| transcriptional control of rad51 expression in the ciliate tetrahymena thermophila. | the expression of rad51p, a dna repair protein that mediates homologous recombination, is induced by dna damage and during both meiosis and exconjugant development in the ciliate tetrahymena thermophila. to completely investigate the transcriptional regulation of tetrahymena rad51 expression, reporter genes consisting of the rad51 5' non-translated sequence (5' nts) positioned upstream of either the firefly luciferase or green fluorescent protein coding sequences have been targeted for recombina ... | 2004 | 15304567 |
| cell division induced by mechanical stimulation in starved tetrahymena thermophila: cell cycle without synthesis of macronuclear dna. | starved tetrahymena thermophila cells underwent synchronous cell division 2 h after a mechanical stimulation. the macronucleus showed no obvious increase in dna content before the cell division in the starvation medium, and the dna content was decreased after the cell division. on the other hand, when the starved cells were given nutrient-supplied medium immediately after the mechanical stimulation, cell division was delayed for 3 h. this period was almost the same as that for g1 cells in the st ... | 2004 | 15261157 |
| factorial designs: an efficient approach to choosing the main factors influencing growth and hydrolase production by tetrahymena thermophila. | a fractional factorial design with eight trials was applied to select and model the effects of major factors, individually and in combination, on improving tetrahymena thermophila growth and enzyme production. regulated ph at 6.8 and olive oil at 0.5% (v/v) showed positive effects on fermentation, and increased cell growth parameters including generation time and maximal population formation. lipase and protease production were also improved by these factors and were favoured by cultivation of t ... | 2004 | 15221666 |
| isolation of a tetrahymena thermophila strain which induced metaphase i meiotic arrest: new pathway of abortive conjugation. | a hypodiploid strain of tetrahymena thermophila has been obtained that shows arrest at the stage of condensed nuclei, corresponding to metaphase i of normal conjugants and induced arrest at meiotic metaphase i (i.e. at the stage of condensed, bivalent chromosomes) in its wt partner mate. the metaphase i arrested conjugants retained their old macronuclei and most of them underwent cell fusion, instead of separation of exconjugants. the doublets were viable and cortically integrated. when the arre ... | 2006 | 15218706 |
| homing endonucleases encoded by germ line-limited genes in tetrahymena thermophila have apetela2 dna binding domains. | three insertion elements were previously found in a family of germ line-limited mobile elements, the tlr elements, in the ciliate tetrahymena. each of the insertions contains an open reading frame (orf). sequence analysis of the deduced proteins encoded by the elements suggests that they are homing endonucleases. the genes are designated tie1-1, tie2-1, and tie3-1 for tetrahymena insertion-homing endonuclease. the endonuclease motif occupies the amino terminal half of each tie protein. the c-ter ... | 2004 | 15189989 |
| the epiplasm gene epc1 influences cell shape and cortical pattern in tetrahymena thermophila. | the cortical protein epc1p is the most abundant protein in the membrane skeleton, or epiplasm, of tetrahymena thermophila. a partial sequence of the epc1 gene was obtained and used to obtain a knockout construct that was successful in transforming tetrahymena thermophila cells. the results support the conclusion that epc1p influences cell shape and the fidelity of cortical development. it was further observed that this protein is transferred from plus to minus cells during conjugation, and that ... | 2004 | 15134256 |
| profilin functions in cytokinesis, nuclear positioning, and stomatogenesis in tetrahymena thermophila. | expression of the actin-binding protein profilin was disrupted in the ciliate tetrahymena thermophila by an antisense ribosome method. in cells with the antisense disruption no profilin protein was detected. cultures of cells with the antisense disruption could be maintained, indicating that profilin was not essential for cytokinesis or vegetative growth. disruption of the expression of profilin resulted in many cells that were large and abnormally shaped. formation of multiple micronuclei, whic ... | 2006 | 15132168 |
| structure of n-glycosidic carbohydrates of secretory proteins of tetrahymena thermophila. | glycoproteins secreted by tetrahymena into the culture medium were isolated and the n-glycosidic oligosaccharides analyzed using lectin blots and fluorophore-assisted carbohydrate gel electrophoresis (face). lectin blots showed that the glycoproteins secreted by tetrahymena contain only n-glycosidic structures of the high mannose type. further analysis using the face technology revealed the presence of four different n-glycosidic structures differing only in the number of mannose residues attach ... | 2004 | 15132165 |
| role of micronucleus-limited dna in programmed deletion of mse2.9 during macronuclear development of tetrahymena thermophila. | extensive programmed dna rearrangements occur during the development of the somatic macronucleus from the germ line micronucleus in the sexual cycle of the ciliated protozoan tetrahymena thermophila. using an in vivo processing assay, we analyzed the role of micronucleus-limited dna during the programmed deletion of mse2.9, an internal eliminated sequence (ies). we identified a 200-bp region within mse2.9 that contains an important cis-acting element which is required for the targeting of effici ... | 2004 | 15075259 |
| evaluating the toxicity of triton x-100 to protozoan, fish, and mammalian cells using fluorescent dyes as indicators of cell viability. | three viability assays using fluorescent dyes effectively detected a loss of viability in cultures of three mammalian cell lines (h4iie, caco2, and hepg-2), two fish cell lines (rtgill-w1 and rtl-w1), and a ciliated protozoan, tetrahymena thermophila, after exposure to triton x-100, used as a model toxicant. the dyes were alamar blue (ab), neutral red (nr), and propidium iodide, which respectively monitored energy metabolism, lysosomal activity, and membrane integrity. a fourth fluorescent dye, ... | 2004 | 15041260 |
| modular structure in developmentally eliminated dna in tetrahymena may be a consequence of frequent insertions and deletions. | the work reported here describes insertion-deletion (indel) polymorphisms in two internally eliminated sequences (iess, that are deleted during development in tetrahymena): a 1.8 kb indel at one end of the 1.1 kb h1 ies and a 0.5 kb indel inside the 1.4 kb calmodulin (c) ies. these two iess are located in the proximity of the h1 histone and calmodulin genes, respectively, and are among the ten iess that have been fully sequenced out of an estimated total of 6000. three hundred base-pairs of the ... | 2004 | 15037070 |
| a member of a repeat family is the source of an insertion-deletion polymorphism inside a developmentally eliminated sequence of tetrahymena thermophila. | in tetrahymena thermophila, the development of a transcriptionally active macronucleus from a transcriptionally inert micronucleus is accompanied by the elimination of numerous dna segments, called internally eliminated sequences (iess), many of which belong to dispersed repetitive sequence families. to examine the relationship between the insertion and deletion events expected to occur during evolution of the repeats and the developmental elimination process, iess were compared among different ... | 2004 | 15037069 |
| properties of the full-length heavy chains of tetrahymena ciliary outer arm dynein separated by urea treatment. | an important challenge is to understand the functional specialization of dynein heavy chains. the ciliary outer arm dynein from tetrahymena thermophila is a heterotrimer of three heavy chains, called alpha, beta and gamma. in order to dissect the contributions of the individual heavy chains, we used controlled urea treatment to dissociate tetrahymena outer arm dynein into a 19s beta/gamma dimer and a 14s alpha heavy chain. the three heavy chains remained full-length and retained mgatpase activit ... | 2004 | 14983522 |
| a non-long terminal repeat retrotransposon family is restricted to the germ line micronucleus of the ciliated protozoan tetrahymena thermophila. | the ciliated protozoan tetrahymena thermophila undergoes extensive programmed dna rearrangements during the development of a somatic macronucleus from the germ line micronucleus in its sexual cycle. to investigate the relationship between programmed dna rearrangements and transposable elements, we identified several members of a family of non-long terminal repeat (ltr) retrotransposons (retroposons) in t. thermophila, the first characterized in the ciliated protozoa. this multiple-copy retrotran ... | 2004 | 14871946 |
| histone h3 lysine 9 methylation is required for dna elimination in developing macronuclei in tetrahymena. | genome-wide dna elimination accompanies development of the somatic macronucleus from the germ-line micronucleus during the sexual process of conjugation in the ciliated protozoan tetrahymena thermophila. small rnas, referred to as "scan rnas" (scnrnas), that accumulate only during conjugation are highly enriched in the eliminated sequences, and mutations that prevent dna elimination also affect the accumulation of scnrnas, suggesting that an rna interference (rnai)-like mechanism is involved in ... | 2004 | 14755052 |
| expression of gfp-actin leads to failure of nuclear elongation and cytokinesis in tetrahymena thermophila. | green fluorescent protein (gfp)-tagged actin was used to investigate the distribution and function of actin in tetrahymena. a strain that expresses both gfp-actin and endogenous actin was developed by transformation of tetrahymena thermophila with a ribosomal dna-based replicative vector. confocal microscopy of living cells and immunogold electron microscopy confirmed localization of gfp-actin to basal bodies and the contractile ring. incorporation of the fusion protein into these and other acti ... | 2006 | 14733431 |
| identification of a developmentally regulated translation elongation factor 2 in tetrahymena thermophila. | protein synthesis elongation factor 2 (eef2) catalyzes the translocation of the peptidyl-trna from the a site to the p site of the ribosome. most organisms encode a single ef2 protein and its activity is regulated by phosphorylation. we have identified a family of genes in tetrahymena thermophila that encode proteins homologous to eef2, yet are expressed only during sexual reproduction. these genes have been designated efr for elongation factor 2 related. efr transcripts were not detected in veg ... | 2004 | 14729267 |
| dephosphorylation of inner arm 1 is associated with ciliary reversals in tetrahymena thermophila. | in many organisms, depolarizing stimuli cause an increase in intraciliary ca2+, which results in reversal of ciliary beat direction and backward swimming. the mechanism by which an increase in intraciliary ca2+ causes ciliary reversal is not known. here we show that tetrahymena cells treated with okadaic acid or cantharidin to inhibit protein phosphatases do not swim backwards in response to depolarizing stimuli. we also show that both okadaic acid and cantharidin inhibit backward swimming in re ... | 2004 | 14691947 |
| application of nmr shapes screening to an rna target. | several nmr screening techniques have been developed in recent years to aid in the identification of lead drug compounds. these nmr methods have traditionally been used for protein targets, and here we examine their applicability for an rna target. we used the shapes compound library to test three different nmr screening methodologies: the saturation transfer difference (std), the 2d trnoesy, and the waterlogsy experiments. we found that the waterlogsy experiment was the most sensitive method fo ... | 2003 | 14677945 |
| cloning and sequencing of four new metallothionein genes from tetrahymena thermophila and t. pigmentosa: evolutionary relationships in tetrahymena mt family. | the structure of four new mt (metallothionein) genes of tetrahymena thermophila and t. pigmentosa were characterized. the mt-2 genes from the two species are very similar, differing by 10 out of 2259 sequenced nucleotides, and the deduced amino acid sequences are identical. the mt-1 genes from t. pigmentosa and t thermophila are also very similar, differing only by 3 nucleotides in the 5'-ut region. the promoter regions contain a tata box and many stretches partially matching some regulatory ele ... | 2003 | 14658499 |
| imaging tetrahymena ribozyme splicing activity in single live mammalian cells. | tetrahymena ribozymes hold promise for repairing genetic disorders but are largely limited by their modest splicing efficiency and low production of final therapeutic proteins. ribozyme evolution in intact living mammalian cells would greatly facilitate the discovery of new ribozyme variants with high in vivo activity, but no such strategies have been reported. here we present a study using a new reporter enzyme, beta-lactamase, to report splicing activity in single living cells and perform high ... | 2003 | 14645710 |
| protein binding to expanded telomere repeats in tetrahymena thermophila. | the ends of eukaryotic chromosomes are protected by dna-protein structures called telomeres. telomeric dna is highly conserved, usually consisting of long tracts of a repeating g-rich sequence. tetrahymena thermophila telomeric dna consists of alternating blocks of gggg and tt sequences (i.e. a g4t2 repeat sequence). we examined the relative importance of the guanine and thymine elements of the repeat sequence in promoting in vitro binding by t. thermophila proteins. we identified single- and, f ... | 2013 | 14563172 |
| biochemical evidence for a p2y-like receptor in tetrahymena thermophila. | extracellular nucleotides are ubiquitous signaling molecules. atp signals through two receptor types: the ionotropic p2x receptors, and the metabotropic p2y receptors. atp acts as a chemorepellent in tetrahymena thermophila, where it causes a distinct avoidance response. the intracellular mechanisms by which atp causes avoidance in this organism, however, are unknown. in this study, we use in vivo pharmacological assays along with enzyme immuno-assays to obtain information about the atp chemorep ... | 2003 | 13680132 |
| the fenestrin antigen in submembrane skeleton of the ciliate tetrahymena thermophila is proposed as a marker of cell polarity during cell division and in oral replacement. | tetrahymena thermophila cells have two types of polarized morphogenesis: divisional morphogenesis and oral reorganization (or). the aim of this research is the analysis of cortical patterns of immunostaining during cell division and in or using previously characterized antibodies against fenestrin and epiplasm b proteins. during cell division, the anarchic field of basal body proliferation of the new developing oral apparatus (af) showed concomitant strong binding of the fenestrin antigen and wi ... | 2003 | 13677452 |
| hypoxia regulates assembly of cilia in suppressors of tetrahymena lacking an intraflagellar transport subunit gene. | we cloned a tetrahymena thermophila gene, ift52, encoding a homolog of the chlamydomonas intraflagellar transport protein, ift52. disruption of ift52 led to loss of cilia and incomplete cytokinesis, a phenotype indistinguishable from that of mutants lacking kinesin-ii, a known ciliary assembly transporter. the cytokinesis failures seem to result from lack of cell movement rather than from direct involvement of ciliary assembly pathway components in cytokinesis. spontaneous partial suppressors of ... | 2003 | 12925756 |
| diverse sequences within tlr elements target programmed dna elimination in tetrahymena thermophila. | tlr elements are a novel family of approximately 30 putative mobile genetic elements that are confined to the germ line micronuclear genome in tetrahymena thermophila. thousands of diverse germ line-limited sequences, including the tlr elements, are specifically eliminated from the differentiating somatic macronucleus. macronucleus-retained sequences flanking deleted regions are known to contain cis-acting signals that delineate elimination boundaries. it is unclear whether sequences within dele ... | 2003 | 12912887 |
| effect of alteration in the global body plan on the deployment of morphogenesis-related protein epitopes labeled by the monoclonal antibody 12g9 in tetrahymena thermophila. | we have employed monoclonal antibodies to reinvestigate the janus mutants of the ciliate tetrahymena thermophila, which cause reversal of circumferential polarity on the dorsal surface of the cell. this reversal brings about frequent ectopic expression of ventral cortical landmarks, such as a "secondary" oral apparatus, on the dorsal surface. the principal antibody employed, fxxxix-12g9, immunolabels both transient cortical structures not directly associated with basal bodies (the fission line a ... | 2003 | 12812371 |
| caspase-like activity in programmed nuclear death during conjugation of tetrahymena thermophila. | apoptosis, or programmed cell death, is common in a variety of eucaryotes, from unicellular protozoa to vertebrates. the ciliated protozoan tetrahymena thermophila has a unique apoptosis-like nuclear death during conjugation, called programmed nuclear death. this death program involves nuclear condensation (pyknosis) and oligonucleosomal dna fragmentation in the parental macronucleus. subsequently, the condensed nucleus is entirely resorbed in the autophagosome. here we demonstrate that caspase- ... | 2003 | 12761572 |
| mechanically probing the folding pathway of single rna molecules. | we study theoretically the denaturation of single rna molecules by mechanical stretching, focusing on signatures of the (un)folding pathway in molecular fluctuations. our model describes the interactions between nucleotides by incorporating the experimentally determined free energy rules for rna secondary structure, whereas exterior single-stranded regions are modeled as freely jointed chains. for exemplary rna sequences (hairpins and the tetrahymena thermophila group i intron), we compute the q ... | 2003 | 12719217 |
| multiple monovalent ion-dependent pathways for the folding of the l-21 tetrahymena thermophila ribozyme. | synchrotron hydroxyl radical (*oh) footprinting is a technique that monitors the local changes in solvent accessibility of the rna backbone on milliseconds to minutes time-scales. the mg(2+)-dependent folding of the l-21 sca 1 tetrahymena thermophila ribozyme has been followed using this technique at an elevated concentration of monovalent ion (200 mm nacl) and as a function of the initial annealing conditions and substrate. previous studies conducted at low concentrations of monovalent ion disp ... | 2003 | 12691754 |
| the nonessential h2a n-terminal tail can function as an essential charge patch on the h2a.z variant n-terminal tail. | tetrahymena thermophila cells contain three forms of h2a: major h2a.1 and h2a.2, which make up approximately 80% of total h2a, and a conserved variant, h2a.z. we showed previously that acetylation of h2a.z was essential (q. ren and m. a. gorovsky, mol. cell 7:1329-1335, 2001). here we used in vitro mutagenesis of lysine residues, coupled with gene replacement, to identify the sites of acetylation of the n-terminal tail of the major h2a and to analyze its function in vivo. tetrahymena cells survi ... | 2003 | 12665578 |
| identifying kinetic barriers to mechanical unfolding of the t. thermophila ribozyme. | mechanical unfolding trajectories for single molecules of the tetrahymena thermophila ribozyme display eight intermediates corresponding to discrete kinetic barriers that oppose mechanical unfolding with lifetimes of seconds and rupture forces between 10 and 30 piconewtons. barriers are magnesium dependent and correspond to known intra- and interdomain interactions. several barrier structures are "brittle," breakage requiring high forces but small (1 to 3 nanometers) deformations. barrier crossi ... | 2003 | 12649482 |
| insulin receptor-like proteins in tetrahymena thermophila ciliary membranes. | | 2003 | 12546802 |
| cloning, localization, and axonemal function of tetrahymena centrin. | centrin, an ef hand ca(2+) binding protein, has been cloned in tetrahymena thermophila. it is a 167 amino acid protein of 19.4 kda with a unique n-terminal region, coded by a single gene containing an 85-base pair intron. it has > 80% homology to other centrins and high homology to tetrahymena ef hand proteins calmodulin, tcbp23, and tcbp25. specific cellular localizations of the closely related tetrahymena ef hand proteins are different from centrin. centrin is localized to basal bodies, cortic ... | 2003 | 12529441 |
| confocal fluorescence microscopy for tetrahymena thermophila. | | 2002 | 12512328 |
| sheared aanti.aanti base pairs in a destabilizing 2 x 2 internal loop: the nmr structure of 5'(rggcaagccu)2. | the 5'(rggcaagccu)(2) duplex contains tandem a.a pairs. the three-dimensional structure of the 5'(rggcaagccu)(2) duplex was modeled by molecular dynamics and energy minimization with nmr-derived distance and dihedral angle restraints. although the 5'(rcaag)(2) loop is thermodynamically destabilizing by 1.1 kcal/mol, the tandem a.a pairs adopt a predominant conformation: a sheared anti-anti (a.a trans hoogsteen/sugar-edge) alignment similar to that observed in the crystal structure of the p4-p6 d ... | 2002 | 12475246 |
| proprotein processing within secretory dense core granules of tetrahymena thermophila. | in the ciliate tetrahymena thermophila, the polypeptides stored in secretory dense core granules (dcgs) are generated by proteolytic processing of precursors, and the mature products assemble as a crystal. previous observations suggested that this maturation involves precise cleavage at distinct motifs by a small number of enzymes. to test these inferences, we analyzed the determinants for site-specific processing of pro-grl1p (granule lattice protein 1) by complete gene replacement with modifie ... | 2003 | 12435750 |
| monovalent cations mediate formation of native tertiary structure of the tetrahymena thermophila ribozyme. | the formation of individual tertiary contacts of the tetrahymena l-21 sca i ribozyme has been monitored by hydroxyl radical footprinting and its global conformation by analytical ultracentrifugation as a function of monovalent ion concentration in the absence of divalent ions. advanced methods of data analysis, which allow the hydroxyl radical reactivity of every nucleotide to be quantified, permit monitoring of each and every structural element of the rna. monovalent ion-mediated global compact ... | 2002 | 12434149 |
| external gtp binding and induction of cell division in starved tetrahymena thermophila. | the extracellular nucleotide, guanosine 5'-triphosphate (gtp) is known to be a chemorepellent for ciliated protozoa such as paramecium and tetrahymena. here, we studied the surface localization of gtp binding sites and also its effects on the cell division of tetrahymena thermophila. when a ribose-modified and fluorescent analog of gtp, 2'-(or -3')-o-trinitrophenyl (tnp)-gtp was added to the cells starved in non-nutrient buffer, a remarkable fluorescence was observed at the compound cilia of the ... | 2002 | 12416728 |
| inner arm dynein 1 is essential for ca++-dependent ciliary reversals in tetrahymena thermophila. | cilia in many organisms undergo a phenomenon called ciliary reversal during which the cilia reverse the beat direction, and the cell swims backwards. ciliary reversal is typically caused by a depolarizing stimulus that ultimately leads to a rise in intraciliary ca++ levels. it is this increase in intraciliary ca++ that triggers ciliary reversal. however, the mechanism by which an increase in intraciliary ca++ causes ciliary reversal is not known. we have previously mutated the dyh6 gene of tetra ... | 2002 | 12378538 |
| tetrahymena thermophila contains a conventional gamma-tubulin that is differentially required for the maintenance of different microtubule-organizing centers. | the gene (gtu1) encoding tetrahymena thermophila gamma-tubulin was cloned and analyzed. gtu1 is a single-copy, essential gene encoding a conventional gamma-tubulin. ha-tagged gtu1p localizes to four microtubule-organizing centers (mtocs) in vegetative cells: basal bodies (bbs), macronuclear envelopes, micronuclear envelopes, and contractile vacuole pores. gamma-tubulin function was studied by placing the gtu1 gene under control of an inducible-repressible promoter. overexpression of gtu1 had no ... | 2002 | 12356864 |
| quantitative structure-activity relationships for the toxicity of nitrobenzenes to tetrahymena thermophila. | in this study igc50 (50% inhibitory growth concentration) values of 26 nitrobenzenes were determined for population growth endpoint of tetrahymena thermophila. the toxicity order of the observed compounds has been found as follows: dinitro compounds > mono-nitro compounds; dichloronitrobenzenes > monochloronitrobenzenes; and meta-substituted nitrobenzenes > ortho-/para-substituted nitrobenzenes (nt, nph, nanis) except for the dinitrobenzenes and nitroanilines (dnb, nan). quantitative structure a ... | 2002 | 12046656 |
| a novel family of mobile genetic elements is limited to the germline genome in tetrahymena thermophila. | in the ciliated protozoan tetrahymena thermophila, extensive dna elimination is associated with differentiation of the somatic macronucleus from the germline micronucleus. this study describes the isolation and complete characterization of tlr elements, a family of approximately 30 micronuclear dna sequences that are efficiently eliminated from the developing macronucleus. the data indicate that tlr elements are comprised of an approximately 22 kb internal region flanked by complex and variable ... | 2002 | 12034842 |
| telomerase recognizes its template by using an adjacent rna motif. | telomerase adds telomeric repeats to chromosome 3' ends, forestalling the cellular senescence, apoptosis, and genomic instability that result from telomere loss caused by incomplete dna replication. the telomerase ribonucleoprotein is dedicated to synthesis of tandem, simple-sequence repeats by virtue of its specialization for copying only a specific template region within the integral rna. here, using circularly permuted variants of tetrahymena thermophila telomerase rna, we identify the featur ... | 2002 | 11997465 |
| linkage of monovalent and divalent ion binding in the folding of the p4-p6 domain of the tetrahymena ribozyme. | we have explored the linkage of monovalent and divalent ion binding in the folding of the p4-p6 domain of tetrahymena thermophila ribozyme by examining the mg2+-induced folding and the urea-induced denaturation of the folded state as a function of na+ under equilibrium folding conditions using hydroxyl radical footprinting. these studies allowed a thermodynamic examination of eight discrete protection sites within p4-p6 that are involved in several tertiary structure contacts. monovalent ions co ... | 2002 | 11980483 |
| polymorphism and selection at the serh immobilization antigen locus in natural populations of tetrahymena thermophila. | the serh locus of tetrahymena thermophila is one of several paralogous loci with genes encoding variants of the major cell surface protein known as the immobilization antigen (i-ag). the locus is highly polymorphic, raising questions concerning functional equivalency and selective forces acting on its multiple alleles. here, we compare the sequences and expression of serh1, serh3, serh4, serh5, and serh6. the precursor i-ags are highly similar. they are rich in alanine, serine, threonine, and cy ... | 2002 | 11973302 |
| both carboxy-terminal tails of alpha- and beta-tubulin are essential, but either one will suffice. | microtubules (mts) are organized into distinct systems essential for cell shape, movement, intracellular transport, and division. electron crystallographic analyses provide little information about how mts produce diverse structures and functions, perhaps because they failed to visualize the last 10 residues of the alpha- and the last 18 of the beta-tubulin c-terminal tails (ctts), which likely play a role in mt diversity. ctts define conserved, nonallelic isotypes in mammals, are major sites of ... | 2002 | 11864572 |
| polyglycylation domain of beta-tubulin maintains axonemal architecture and affects cytokinesis in tetrahymena. | polyglycylation occurs through the post-translational addition of a polyglycine peptide to the gamma-carboxyl group of glutamic acids near the c terminus of alpha- and beta-tubulin, and has been found only in cells with axonemes, from protists to humans. in tetrahymena thermophila, multiple sites of polyglycylation on alpha-tubulin are dispensable. by contrast, mutating similar sites on beta-tubulin has site-specific effects, affecting cell motility and cytokinesis, or resulting in cell death. h ... | 2002 | 11862218 |
| functional genomics: the coming of age for tetrahymena thermophila. | over the past decade, researchers have manipulated the unique biology of tetrahymena thermophila to generate a premier experimental organism for functional genomic analysis. a diverse array of dna transformation methods have spearheaded in vivo strategies for discovering and dissecting universal eukaryotic processes, such as telomere addition and chromatin remodeling. compartmentalization of this protist's genome into two functionally distinct nuclei - the silent 'germline' micronucleus and the ... | 2002 | 11750699 |
| regulation of monomeric dynein activity by atp and adp concentrations. | axonemal dyneins are force-generating atpases that produce ciliary and flagellar movement. a dynein has large heavy chain(s) in which there are multiple (4-6) atp-binding consensus sequences (p-loops) as well as intermediate and light chains, constituting a very large complex. we purified a monomeric form of dynein (dynein-a) that has at least three light chains from 14s dyneins of tetrahymena thermophila and characterized it. in in vitro motility assays, dynein-a rotated microtubules around the ... | 2001 | 11746663 |
| cloning and biochemical analysis of the tetrahymena origin binding protein tif1: competitive dna binding in vitro and in vivo to critical rdna replication determinants. | cis-acting type i elements regulate the initiation of dna replication, replication fork movement, and transcription of the tetrahymena thermophila rdna minichromosome and are required for cell cycle-controlled replication and developmentally programmed gene amplification. previous studies identified three in vitro single-stranded type i element binding activities that were proposed to play distinct roles in replication control. here we describe the cloning of one of these genes, tif1, and we pro ... | 2001 | 11577092 |
| targeted gene knockout of inner arm 1 in tetrahymena thermophila. | cilia and flagella contain at least eight different types of dynein arms. it is not entirely clear how the different types of arms are organized along the axoneme. in addition, the role each different type of dynein plays in ciliary or flagellar motility is not known. to initiate studies of dynein organization and function in cilia, we have introduced a mutation into one dynein heavy chain gene (dyh6) in tetrahymena themophila by targeted gene knockout. we have generated mutant cells that lack w ... | 2001 | 11499791 |
| g-overhang dynamics at tetrahymena telomeres. | to learn more about the structure of the dna terminus at tetrahymena thermophila telomeres, we have devised a ligation-mediated primer extension protocol to accurately measure the length of the g-strand overhang. we show that overhang length and the identity of the 3'-terminal nucleotide are tightly regulated. the majority of overhangs terminate in the sequence 5'-ttggggt and >80% are either 14-15 or 20-21 nucleotides in length. no significant changes in overhang length were detected as cells tr ... | 2001 | 11483532 |
| purification of gvbd-inducing protein from the ciliate tetrahymena thermophila. | germinal-vesicle-breakdown (gvbd) was induced if a 132,000-g supernatant of tetrahymena thermophila homogenates was injected into xenopus oocytes. using this induction of gvbd as a bioassay system, a gvbd-inducing substance was purified from the tetrahymena by ultra-filtration, liquid chromatography, and electroelution from a band on native-page gel. proteins eluted from the single band on the native-page gel induced gvbd in the absence of oocyte protein synthesis. this band resolved into two ba ... | 2006 | 11456317 |
| an antisense approach to phenotype-based gene cloning in tetrahymena. | we report a pioneering approach using tetrahymena thermophila that permits rapid identification of genes based on their null or hypomorphic phenotypes. this technique involves cell transformation with a library of plasmids that encode 26s ribosomal subunits containing short insertions. the insertions correspond to antisense sequences for a large number of genes. the majority of cells each acquires a single antisense sequence, which silences a single genomic locus. because the insertion site with ... | 2001 | 11438705 |
| development in electrofused conjugants of tetrahymena thermophila. | electric shock can create parabiotic fusions of living tetrahymena cells. in this study, cells were mated and successful pairs were electrofused with either vegetatively growing cells or other mating pairs. in particular, we electrofused pairs from normal [diploid x diploid] matings with vegetatively dividing cells in g- or m-phase of the cell cycle. we also fused [diploid x diploid] conjugants with mating pairs involving an aneuploid partner [diploid x "star"], which typically undergo an aborti ... | 2006 | 11411835 |
| product analysis illuminates the final steps of ies deletion in tetrahymena thermophila. | dna sequences (ies elements) eliminated from the developing macronucleus in the ciliate tetrahymena thermophila are released as linear fragments, which have now been detected and isolated. a pcr-mediated examination of fragment end structures reveals three types of strand scission events, reflecting three steps in the deletion process. new evidence is provided for two steps proposed previously: an initiating double-stranded cleavage, and strand transfer to create a branched deletion intermediate ... | 2001 | 11406601 |
| cell death in tetrahymena thermophila: new observations on culture conditions. | we previously suggested that the cell fate of the protozoan ciliate, tetrahymena thermophila, effectively relates to a quorum-sensing mechanism where cell-released factors support cell survival and proliferation. the cells have to be present above a critical initial density in a chemically defined nutrient medium in order to release a sufficient level of these factors to allow a new colony to flourish. at a relatively high rate of metabolism and/or macromolecular synthesis and below this critica ... | 2001 | 11407856 |
| chemorepellent signaling through the pacap/lysozyme receptor is mediated through camp and pkc in tetrahymena thermophila. | pituitary adenylate cyclase-activating peptide and lysozyme are potent chemorepellents which act through the same receptor in tetrahymena. using in vivo behavioral studies, we have found that the pituitary adenylate cyclase-activating peptide/lysozyme receptor appears to signal through a g-protein pathway which is mediated through both adenosine 3'5'monophosphate and protein kinase c. avoidance to pituitary adenylate cyclase-activating peptide and lysozyme is inhibited by the g-protein inhibitor ... | 2001 | 11401196 |
| nongenic, bidirectional transcription precedes and may promote developmental dna deletion in tetrahymena thermophila. | a large number of dna segments are excised from the chromosomes of the somatic nucleus during development of tetrahymena thermophila. how these germline-limited sequences are recognized and excised is still poorly understood. we have found that many of these noncoding dnas are transcribed during nuclear development. transcription of the germline-limited m element occurs from both dna strands and results in heterogeneous transcripts of < 200 b to > 1 kb. transcripts are most abundant when develop ... | 2001 | 11358871 |
| reversible unfolding of single rna molecules by mechanical force. | here we use mechanical force to induce the unfolding and refolding of single rna molecules: a simple rna hairpin, a molecule containing a three-helix junction, and the p5abc domain of the tetrahymena thermophila ribozyme. all three molecules (p5abc only in the absence of mg2+) can be mechanically unfolded at equilibrium, and when kept at constant force within a critical force range, are bi-stable and hop between folded and unfolded states. we determine the force-dependent equilibrium constants f ... | 2001 | 11326101 |
| lysosomal enzymes in the macronucleus of tetrahymena during its apoptosis-like degradation. | a key characteristic of apoptosis is its regulated nuclear degradation. apoptosis-like nuclear degradation also occurs in the ciliated unicellular organism, tetrahymena thermophila. chromatin of the macronucleus undergoes massive condensation, a process that can be blocked by caspase inhibitors. the nucleus becomes tunel-positive, and its dna is cleaved into nucleosome-sized fragments. in a matter of hours the macronucleus is completely degraded, and disappears. the condensed nucleus sequesters ... | 2001 | 11319612 |
| gamma-linolenic acid biosynthesis: cryptoregiochemistry of delta6 desaturation. | the valuable nutraceutical gamma-linolenic acid (gla, (6z,9z,12z)-octadecatrienoic acid) is biosynthesized by a series of regio- and stereoselective dehydrogenation reactions that are catalyzed by a set of enzymes known as fatty acid desaturases. as part of ongoing research into the mechanism of these remarkable catalysts, we have examined the cryptoregiochemistry (site of initial oxidation) of delta6 desaturation as it occurs in the protozoan tetrahymena thermophila. two complementary approache ... | 2001 | 11312950 |
| the transition from conjugal development to the first vegetative cell division is dependent on rad51 expression in the ciliate tetrahymena thermophila. | rad51p, the eukaryotic homolog of the prokaryotic reca protein, catalyzes strand exchange between single- and double-stranded dna and is involved in both genetic recombination and double-strand break repair in the ciliate tetrahymena thermophila. we have previously shown that disruption of the tetrahymena rad51 somatic macronuclear locus leads to defective germline micronuclear division and that conjugation of two somatic rad51 null strains results in an early meiotic arrest. we have constructed ... | 2001 | 11290715 |
| structural basis of the enhanced stability of a mutant ribozyme domain and a detailed view of rna--solvent interactions. | the structure of p4-p6, a 160 nucleotide domain of the self-splicing tetrahymena thermophila intron, was solved previously. mutants of the p4-p6 rna that form a more stable tertiary structure in solution were recently isolated by successive rounds of in vitro selection and amplification. | 2001 | 11286889 |
| formation of a gnra tetraloop in p5abc can disrupt an interdomain interaction in the tetrahymena group i ribozyme. | the secondary structure of a truncated p5abc subdomain (tp5abc, a 56-nucleotide rna) of the tetrahymena thermophila group i intron ribozyme changes when its tertiary structure forms. we have now used heteronuclear nmr spectroscopy to determine its conformation in solution. the tp5abc rna that contains only secondary structure is extended compared with the tertiary folded form; both forms coexist in slow chemical exchange (the interconversion rate constant is slower than 1 s(-1)) in the presence ... | 2001 | 11274387 |
| a regulatory light chain of ciliary outer arm dynein in tetrahymena thermophila. | ciliary beat frequency is primarily regulated by outer arm dyneins (22 s dynein). chilcote and johnson (chilcote, t. j., and johnson, k. a. (1990) j. biol. chem. 256, 17257-17266) previously studied isolated tetrahymena 22 s dynein, identifying a protein p34, which showed camp-dependent phosphorylation. here, we characterize the molecular biochemistry of p34 further, demonstrating that it is the functional ortholog of the 22 s dynein regulatory light chain, p29, in paramecium. p34, thiophosphory ... | 2001 | 11274140 |
| determination of macromolecular folding and structure by synchrotron x-ray radiolysis techniques. | radiolysis of water by synchrotron x-rays generates oxygen-containing radicals that undergo reactions with solvent accessible sites of macromolecules inducing stable covalent modifications or cleavage on millisecond time scales. the extent and site of these reactions are determined by gel electrophoresis and mass spectrometry analysis. these data are used to construct a high-resolution map of solvent accessibility at individual reactive sites. the experiments can be performed in a time-resolved ... | 2001 | 11161303 |
| genetic and environmental factors affecting mating type frequency in natural isolates of tetrahymena thermophila. | in tetrahymena thermophila mating type alleles specify temperature sensitive frequency distributions of multiple mating types. a-like alleles specify mating types i, ii, iii, v and vi, whereas b-like alleles specify mating types ii through vii. we have characterized the mating type distributions specified by several a- and b-like genotypes segregated by genomic exclusion from cells isolated from a pond in northwestern pennsylvania. the b-like genotypes are alike in specifying very low frequencie ... | 2006 | 11140456 |
| toward sequencing the tetrahymena genome: exploiting the gift of nuclear dimorphism. | important scientific discoveries have utilized the unique advantages of tetrahymena thermophila as a research organism. recently developed molecular genetic manipulations allow full exploitation of the many scientific dividends that would result from having its genome sequenced. as a typical ciliated protozoan, tetrahymena exhibits "nuclear dimorphism". it possesses two differentiated forms of its nuclear genome: a globally repressed, diploid germline or micronuclear genome, and a polyploid, sit ... | 2007 | 11140445 |
| cis-acting requirements in flanking dna for the programmed elimination of mse2.9: a common mechanism for deletion of internal eliminated sequences from the developing macronucleus of tetrahymena thermophila. | during macronuclear development in the ciliated protozoan tetrahymena thermophila, extensive dna deletions occur, eliminating thousands of internal eliminated sequences (iess). using an rdna-based transformation assay we have analyzed the role during dna deletion of dna flanking mse2.9, an ies within the second intron of a gene encoding an as yet incompletely characterized protein. we establish that a cis-acting sequence for mse2.9 deletion acts at a distance to specify deletion boundaries. a co ... | 2001 | 11139619 |
| the role of cortical geometry in the nuclear development of tetrahymena thermophila. | vegetative cells were subjected to electrofusion and the resulting heteropolar doublets were then mated to normal single cells and followed throughout conjugation using cytological and genetic techniques. the unique cyto-geometry created in a heteropolar doublet--a continuous cytoplasmic compartment bounded by two anterior poles and sharing a fused posterior pole at midbody, and the potential for two conjugal exchange junctions--resulted in instructive perturbations of nuclear behavior. our resu ... | 2006 | 11128713 |
| myo1, a novel, unconventional myosin gene affects endocytosis and macronuclear elongation in tetrahymena thermophila. | targeted gene disruption was used to investigate the function of myo1, an unconventional myosin gene in tetrahymena thermophila. phenotypic analysis of a transformed strain that lacked a functional myo1 gene was conducted at both 20 degrees c and 35 degrees c. at either temperature the delta myo1 strain had a smaller cytoplasm/nucleus ratio than wild type. at 20 degrees c, delta myo1 populations had a longer doubling time than wild type, lower saturation density, and a reduced rate of food vacuo ... | 2013 | 11128708 |
| activation of prostacyclin synthesis by mechanical stimulation in the ciliated protozoan tetrahymena thermophila. | we detected a hplc peak corresponding to 6-keto-pgf(1alpha), a stable metabolite of prostacyclin (pgi(2)), in [1-(14)c]arachidonate metabolites from the ciliated protozoan tetrahymena thermophila. quantitative analysis of 6-keto-pgf(1alpha) by enzyme immunoassay revealed that the synthesis and release were rapidly activated by the mechanical stimulation of a short centrifugation. the activation was suppressed significantly by a cyclooxygenase inhibitor, ibuprofen, and was independent of the extr ... | 2000 | 11118337 |
| molecular characterization of the serl paralogs of tetrahymena thermophila. | in the pond ciliate tetrahymena thermophila, expression of genes encoding variant forms of the cell surface immobilization antigen (i-ag) is regulated by environmental conditions. multiple isoforms of the l i-ags are found on the surface of cells grown at <20 degrees c as well as on the surface of rsec mutants which express serl genes constitutively. five cdnas encoding variant l i-ags of rsec were sequenced and their expression studied. two additional serl genes from natural isolates were seque ... | 2000 | 11095959 |
| screening for and characterization of phospholipase a1 hypersecretory mutants of tetrahymena thermophila. | we have described a procedure for the isolation of mutants of tetrahymena thermophila with hypersecretion of phospholipase a1 (pla1). using random chemical mutagenesis, uniparental cytogamy, genetic crossing and a new, fast and effective screening procedure, four pla1-hypersecretory mutants were isolated. the screening procedure is based on the formation of a halo appearing around cylindrical holes in a lecithin-containing agar plate filled with cell-free supernatants. about 3,940 clones were te ... | 2000 | 11030577 |
| the road to rnase p. | in 1989, sidney altman and thomas r. cech shared the nobel prize in chemistry for their discovery of catalytic properties of rna. cech was studying the splicing of rna in a unicellular organism called tetrahymena thermophila. he found that the precursor rna could splice in vitro in the absence of proteins. altman studied ribonuclease p (rnase p), a ribonucleoprotein that is a key enzyme in the biosynthesis of trna. rnase p is an rna processing endonuclease that specifically cleaves precursors of ... | 2000 | 11017184 |
| two tetrahymena g-dna-binding proteins, tgp1 and tgp3, share novel motifs and may play a role in micronuclear division. | g-dna is a four-stranded dna structure with diverse putative biological roles. we have previously purified and cloned a novel g-dna-binding protein tgp1 from the ciliate tetrahymena thermophila. here we report the molecular cloning of tgp3, an additional g-dna-binding protein from the same organism. the tgp3 cdna encodes a 365 amino acid protein that is homologous to tgp1 (34% identity and 44% similarity). the proteins share a sequence pattern that contains two novel repetitive and homologous mo ... | 2000 | 10908364 |
| replicability and recurrence in the experimental evolution of a group i ribozyme. | in order to explore the variety of possible responses available to a ribozyme population evolving a novel phenotype, five tetrahymena thermophila group i intron ribozyme pools were evolved in parallel for cleavage of a dna oligonucleotide. these ribozyme populations were propagated under identical conditions and characterized when they reached apparent phenotypic plateaus; the populations that reached the highest plateau showed a near 100-fold improvement in dna cleavage activity. a detailed cha ... | 2000 | 10889218 |
| autonomously replicating macronuclear dna pieces are the physical basis of genetic coassortment groups in tetrahymena thermophila. | the macronucleus of the ciliate tetrahymena thermophila contains a fragmented somatic genome consisting of several hundred identifiable chromosome pieces. these pieces are generated by site-specific fragmentation of the germline chromosomes and most of them are represented at an average of 45 copies per macronucleus. in the course of successive divisions of an initially heterozygous macronucleus, the random distribution of alleles of loci carried on these copies eventually generates macronuclei ... | 2000 | 10880474 |
| three telomerases with completely non-telomeric template replacements are catalytically active. | telomerase is a reverse transcriptase minimally composed of a reverse transcriptase protein subunit and an internal rna component that contains the templating region. point mutations of template rna bases can cause loss of enzymatic activity, reduced processivity and misincorporation in vitro. here we report the first complete replacement of the nine base tetrahymena: thermophila telomerase templating region in vivo with non-telomeric sequences. rather than ablating telomerase activity, three su ... | 2000 | 10856255 |
| a single-molecule study of rna catalysis and folding. | using fluorescence microscopy, we studied the catalysis by and folding of individual tetrahymena thermophila ribozyme molecules. the dye-labeled and surface-immobilized ribozymes used were shown to be functionally indistinguishable from the unmodified free ribozyme in solution. a reversible local folding step in which a duplex docks and undocks from the ribozyme core was observed directly in single-molecule time trajectories, allowing the determination of the rate constants and characterization ... | 2000 | 10856219 |
| isolation of a delta7-cholesterol desaturase from tetrahymena thermophila. | cell-free preparations of tetrahymena thermophila catalyze the direct desaturation of cholesterol to delta7-dehydrocholesterol (provitamin d3). the activity was isolated in the microsomal fraction from tetrahymena homogenates. delta7-desaturase activity was stimulated fivefold by the addition of 6 mm atp. other cofactors assayed, including nad, nadp, nadh or nadph, had no significant effect. the activity was found in microsomes prepared from stationary-phase cultures of the ciliate, grown either ... | 2000 | 10855720 |
| molecular mechanisms of microtubular organelle assembly in tetrahymena. | thanks to recent technological advances, the ciliate tetrahymena thermophila has emerged as an attractive model organism for studies on the assembly of microtubular organelles in a single cell. tetrahymena assembles 17 types of distinct microtubules, which are localized in cilia, cell cortex, nuclei, and the endoplasm. these diverse microtubules have distinct morphologies, stabilities, and associations with specific microtubule-associated proteins. for example, kinesin-111, a microtubular motor ... | 2007 | 10847334 |
| polyglycylation of tubulin is essential and affects cell motility and division in tetrahymena thermophila. | we analyzed the role of tubulin polyglycylation in tetrahymena thermophila using in vivo mutagenesis and immunochemical analysis with modification-specific antibodies. three and five polyglycylation sites were identified at glutamic acids near the cooh termini of alpha- and beta-tubulin, respectively. mutants lacking all polyglycylation sites on alpha-tubulin have normal phenotype, whereas similar sites on beta-tubulin are essential. a viable mutant with three mutated sites in beta-tubulin showe ... | 2000 | 10831613 |
| a novel chromodomain protein, pdd3p, associates with internal eliminated sequences during macronuclear development in tetrahymena thermophila. | conversion of the germ line micronuclear genome into the genome of a somatic macronucleus in tetrahymena thermophila requires several dna rearrangement processes. these include (i) excision and subsequent elimination of several thousand internal eliminated sequences (iess) scattered throughout the micronuclear genome and (ii) breakage of the micronuclear chromosomes into hundreds of dna fragments, followed by de novo telomere addition to their ends. chromosome breakage sequences (cbs) that deter ... | 2000 | 10805754 |
| stability and cooperativity of individual tertiary contacts in rna revealed through chemical denaturation. | for proteins, understanding tertiary interactions involved in local versus global unfolding has become increasingly important for understanding the nature of the native state ensemble, the mechanisms of unfolding, and the stability of both the native and intermediate states in folding. in this work we have addressed related questions with respect to rna structure by combining chemical denaturation and hydroxyl radical footprinting methods. we have determined unfolding isotherms for each of 26 di ... | 2000 | 10802732 |
| are cells rescued from 'low density death' by co-operation between phospholipases c and d? | cells of the ciliate tetrahymena thermophila die when transferred at low density to a lipid-free nutritionally complete medium. this death is prevented and they will start to proliferate if protein kinase c is activated and this activation is sustained. we propose that this takes place in two stages. firstly, the phospholipase c pathway beginning with and specific for phosphatidylinositol leads to the formation of diacylglycerol and inositol tris -phosphate. diacylglycerol activates protein kina ... | 2000 | 10772772 |
| rotokinesis, a novel phenomenon of cell locomotion-assisted cytokinesis in the ciliate tetrahymena thermophila. | the mechanism responsible for final cell separation at the end of cytokinesis is currently unknown. knockout strains of the ciliate, tetrahymena thermophila lacking the kinesin-ii homologous molecular motors, kin1p and kin2p are paralyzed due to their complete loss of cilia and undergo frequent cytokinesis failures. observations of live dividing cells revealed that cleavage furrow ingression is normal in kinesin-ii double knockout cells until the final stage of cell separation (brown et al., 199 ... | 1999 | 10772758 |
| tetrahymena macronuclear genome mapping: colinearity of macronuclear coassortment groups and the micronuclear map on chromosome 1l. | the genetics of the ciliate tetrahymena thermophila are richer than for most other eukaryotic cells, because tetrahymena possesses two genomes: a germline (micronuclear) genome that follows a mendelian model of genetic transmission and a somatic (macronuclear) genome, derived from the micronuclear genome by fragmentation, which follows a different genetic transmission model called phenotypic assortment. while genetic markers in the micronucleus fall into classical linkage groups under meiotic re ... | 2000 | 10757760 |
| tetrahymena micronuclear genome mapping. a high-resolution meiotic map of chromosome 1l. | the ciliate tetrahymena thermophila is a useful model organism that combines diverse experimental advantages with powerful capabilities for genetic manipulation. the genetics of tetrahymena are especially rich among eukaryotic cells, because it possesses two distinct but related nuclear genomes within one cytoplasm, contained separately in the micronucleus (mic) and the macronucleus (mac). in an effort to advance fulfillment of tetrahymena's potential as a genetic system, we are mapping both gen ... | 2000 | 10757759 |
| macronuclear development in conjugants of tetrahymena thermophila, which were artificially separated at meiotic prophase. | conjugant pairs of tetrahymena thermophila were mechanically separated by vigorous pipetting at the early stages of meiotic prophase. the complete sequence of conjugational nuclear events including the appearance of pronuclei, development of the new macronuclei (postzygotic development), and resorption of the old macronuclei was observed in the separated cells, without pronuclear exchange. the pronuclei in the separated cells were recognised by the presence of components of the extranuclear cyto ... | 2006 | 10750841 |
| ribosome synthesis in tetrahymena: a quantitative analysis. | we have performed a detailed quantitative analysis of the transcription and accumulation of ribosomal rna and ribosomal protein mrna in the ciliated protozoan tetrahymena thermophila during changes in growth conditions, and found that: (1) nutritional downshifts lead to a rapid decrease in transcriptional activity whereas nutritional upshifts lead to rapid restoration of transcriptional activity, (2) starvation leads to decreased translation of ribosomal protein mrna and (3) the rate of ribosoma ... | 2000 | 10736197 |
| the tetrahymena homolog of bacterial and mammalian 4-hydroxyphenylpyruvate dioxygenases localizes to membranes of the endoplasmic reticulum. | the expression and intracellular localization of the tetrahymena homolog of 4-hydroxyphenylpyruvate dioxygenase (hppd) were investigated in wild-type tetrahymena thermophila strain b1868 vii and the mutant strains iig8, defective in food vacuole formation, ms-1, blocked in secretion of lysosomal enzymes, and sb 281, defective in mucocyst maturation. immunoelectron microscopy and confocal laser scanning microscopy demonstrated that tetrahymena hppd primarily localized to membranes of the endoplas ... | 2000 | 10736196 |
| cloning and characterization of the gene encoding the highly expressed ribosomal protein l3 of the ciliated protozoan tetrahymena thermophila. evidence for differential codon usage in highly expressed genes. | we have cloned and characterized the cdna and the macronuclear genomic copy of the highly conserved ribosomal protein (r-protein) l3 of tetrahymena thermophila. the r-protein l3 is encoded by a single copy gene interrupted by one intron. the organization of the promoter region exhibits features characteristic of ribosomal protein genes in tetrahymena. the codon usage of the l3 gene is highly biased. a thorough analysis of codon usage in tetrahymena genes revealed that genes could be categorized ... | 1999 | 10704239 |
| pacap-38 is a chemorepellent and an agonist for the lysozyme receptor in tetrahymena thermophila. | pituitary adenylate cyclase activating peptide (pacap-38) is a peptide hormone which functions in many mammalian systems, including the nervous and digestive systems. using in vivo behavioral studies, we have found that this hormone functions as a chemore-pellent in tetrahymena thermophila with an ec50 of 10 nm. cells previously adapted to pacap-38 were found to be adapted to lysozyme and vice versa. furthermore, the in vivo behavioral activity of pacap-38 was blocked by addition of the anti-lys ... | 2000 | 10659041 |
| a long stringent sequence signal for programmed chromosome breakage in tetrahymena thermophila. | programmed chromosome breakage occurs at 50-200 specific sites in the genome of tetrahymena thermo-phila during somatic nuclear (macronuclear) differentiation. previous studies have identified a 15 bp sequence, the cbs (for chromosome breakage sequence), that is necessary and sufficient to specify these sites. in this study we determined the effects of mutations in the cbs on its ability to specify the chromosome breakage site and promote new telomere formation in conjugating cells. twenty-one c ... | 2000 | 10648780 |
| three different proteins recognize a multifunctional determinant that controls replication initiation, fork arrest and transcription in tetrahymena. | type i elements regulate the initiation of dna replication, elongation of replication forks and transcription of the tetrahymena thermophila rdna minichromosome. previous studies identified a 24 kda protein, ssa-tibf, which binds the a-rich strand of type i elements. here we describe two additional type i element binding activities (native mol. wt approximately 65 and approximately 250 kda) that interact with dna via previously unidentified 32 and 110 kda polypeptides. the 65 kda activity was pu ... | 2000 | 10637338 |
| allele-specific protein-dna interactions between the single-stranded dna-binding protein, ssa-tibf, and dna replication determinants in tetrahymena. | type i elements are multifunctional, cis-acting determinants that regulate the initiation of dna replication, replication fork movement and transcription of the tetrahymena thermophila rdna minichromosome. previous studies identified a protein, ssa-tibf, that binds specifically to the a-rich strand of type i elements. here, we examine interactions of ssa-tibf with the wild-type c3 allele, and a natural variant, b rdna, which manifests a defect in replication initiation and fork pausing. purified ... | 2000 | 10623536 |
| adenylate kinase is tightly bound to axonemes of tetrahymena cilia. | cilia of tetrahymena thermophila possess adenylate kinase [atp:amp phosphotransferase, ec 2.7.4.3] activity. more than 95% of the total activity was recovered in the axonemal fraction when cilia were demembranated with 0.2% nonidet p-40. there was no loss of the specific activity of adenylate kinase when axonemes were thoroughly washed with hmek solution (10 mm hepes, 5 mm mgcl2, 0.1 mm edta, and 0.1 m kcl, ph 7.4). these results suggest that adenylate kinase is tightly bound to axoneme. solubil ... | 1999 | 10584302 |