| the dynein heavy chain gene family in tetrahymena thermophila. | the dynein atpases are a family of motor enzymes that drive microtubule sliding in cilia and flagella and contribute to microtubule-based transport inside cells. the multi-dynein hypothesis makes two predictions: 1) axonemes contain multiple dynein heavy chain (dhc) isoforms, each encoded by a different gene; 2) each isoform performs a specific role in ciliary beating. we used pcr-based techniques to clone thirteen different dhc sequences from tetrahymena genomic dna. all thirteen genes appeared ... | 2009 | 10568033 |
| a cytogenetic study of development in mechanically disrupted pairs of tetrahymena thermophila. | we examined the nuclear behavior of mating tetrahymena cells that had been mechanically disrupted at various times throughout conjugation. disruption was achieved by agitating conjugating tetrahymena in the presence of 0.1-3 mm glass beads. two minutes of agitation with 1 mm beads yielded optimal pair disruption (70%) with high viability (92%). disrupting pairs between 0-4.7 h after the initiation of mating produced mostly disrupted conjugants in which development was aborted. however, as many a ... | 2006 | 10568032 |
| nucleosome positioning is independent of histone h1 in vivo. | nucleosome positioning in the somatic macronuclear genome of the ciliated protozoan tetrahymena thermophila was analyzed by indirect end labeling. nucleosomes were positioned nonrandomly in three different regions of the tetrahymena genome. nucleosome repeat length varied between adjacent nucleosomes. nucleosome positioning in a histone h1 knockout strain was indistinguishable from that in a strain with wild type histone h1. | 1999 | 10551870 |
| novel aberrant nuclear behavior in abortive conjugation of tetrahymena thermophila: joint selection of a meiotic product and macronucleus during nuclear selection. | in conjugation of tetrahymena thermophila, the paroral zone, cortical cytoplasm in the vicinity of the cytostome, is the site where nuclear selection occurs; one of the four meiotic products is selected in this site prior to the production of gametic pronuclei. during inbreeding cross experiments, several sterile strains were obtained which showed aberrant nuclear behavior. conjugants of these strains normally underwent meiosis, resulting in the generation of four meiotic products. they, however ... | 1999 | 10549130 |
| identification of an essential proximal sequence element in the promoter of the telomerase rna gene of tetrahymena thermophila. | telomerase is a ribonucleoprotein reverse transcriptase that synthesizes and maintains telomeric dna. studies of telomeres and telomerase are facilitated by the large number of linear dna molecules found in ciliated protozoa, such as tetrahymena thermophila. to examine the expression of telomerase, we investigated the transcription of the rna polymerase iii-directed gene encoding the rna subunit (ter1) of this enzyme. a chimeric gene containing the glaucoma chattoni ter1 transcribed region flank ... | 1999 | 10518620 |
| kinesin-ii is preferentially targeted to assembling cilia and is required for ciliogenesis and normal cytokinesis in tetrahymena. | we cloned two genes, kin1 and kin2, encoding kinesin-ii homologues from the ciliate tetrahymena thermophila and constructed strains lacking either kin1 or kin2 or both genes. cells with a single disruption of either gene showed partly overlapping sets of defects in cell growth, motility, ciliary assembly, and thermoresistance. deletion of both genes resulted in loss of cilia and arrests in cytokinesis. mutant cells were unable to assemble new cilia or to maintain preexisting cilia. double knocko ... | 1999 | 10512852 |
| codon usage in tetrahymena thermophila. | | 2000 | 10503219 |
| genetic nomenclature rules for tetrahymena thermophila. | | 2000 | 10503218 |
| creation and use of antisense ribosomes in tetrahymena thermophila. | | 2000 | 10503216 |
| transient and stable dna transformation of tetrahymena thermophila by electroporation. | | 2000 | 10503213 |
| microinjection of tetrahymena thermophila. | | 2000 | 10503212 |
| preparation of cytoskeletal fractions from tetrahymena thermophila. | | 2000 | 10503209 |
| regulated protein secretion in tetrahymena thermophila. | | 2000 | 10503203 |
| cell biology of tetrahymena thermophila. | | 2000 | 10503189 |
| long range cooperative interactions regulate the initiation of replication in the tetrahymena thermophila rdna minichromosome. | the tetrahymena thermophila rdna exists as a 21 kb palindromic minichromosome with two initiation sites for replication in each half palindrome. these sites localize to the imperfect, repeated 430 bp segments that include the nucleosome-free domains 1 and 2 (d1 and d2). to determine if the d1 and d2 segments act independently or in concert to control initiation, stable dna transformation assays were performed. single domain derivatives of the plasmid prd1 failed to support autonomous replication ... | 1999 | 10454603 |
| staurosporine-induced cell death in tetrahymena thermophila has mixed characteristics of both apoptotic and autophagic degeneration. | staurosporine blocks signal transduction associated with cell survival, proliferation and chemosensory behaviour in the ciliated protozoan, tetrahymena thermophila. staurosporine inhibits cell proliferation and in vivo protein phosphorylation induced by phorbol ester. it also reduces the in vitro phosphorylation of the pkc-specific substrate, myelin basic protein fragment 4-14. our results show that cell death in the presence of staurosporine is associated with morphological and ultrastructural ... | 1998 | 10452827 |
| in vitro selection of rnas with increased tertiary structure stability. | an in vitro selection system was devised to select rnas based on their tertiary structural stability, independent of rna activity. selection studies were conducted on the p4-p6 domain from the tetrahymena thermophila group i intron, an autonomous self-folding unit that contains several important tertiary folding motifs including the tetraloop receptor and the a-rich bulge. partially randomized p4-p6 molecules were selected based on their ability to fold into compact structures using native gel e ... | 1999 | 10445885 |
| flanking regulatory sequences of the tetrahymena r deletion element determine the boundaries of dna rearrangement. | in the ciliate tetrahymena thermophila, thousands of dna segments of variable size are eliminated from the developing somatic macronucleus by specific dna rearrangements. it is unclear whether rearrangement of the many different dna elements occurs via a single mechanism or via multiple rearrangement systems. in this study, we characterized in vivo cis-acting sequences required for the rearrangement of the 1.1-kbp r deletion element. we found that rearrangement requires specific sequences flanki ... | 1999 | 10409752 |
| analysis of genomic g + c content, codon usage, initiator codon context and translation termination sites in tetrahymena thermophila. | in recent years, the amount of molecular sequencing data from tetrahymena thermophila has dramatically increased. we analyzed g + c content, codon usage, initiator codon context and stop codon sites in the extremely a + t rich genome of this ciliate. average g + c content was 38% for protein coding regions, 21% for 5' non-coding sequences, 19% for 3' non-coding sequences, 15% for introns, 19% for micronuclear limited sequences and 17% for macronuclear retained sequences flanking micronuclear spe ... | 2006 | 10377985 |
| chemosensory responses of tetrahymena thermophila to cb2, a 24-amino-acid fragment of lysozyme. | while lysozyme is a depolarizing chemorepellent in tetrahymena, the entire lysozyme molecule is not necessary to activate the lysozyme receptor. reduced lysozyme was cut into three fragments by cyanogen bromide cleavage and the fragments (cb1, cb2 and cb3) were separated by hplc. behavioral bioassays showed that the carboxy-terminal 24-amino-acid fragment, which we call cb2, is 100 times more active than intact lysozyme as a chemorepellent. cb2 appears to activate the same receptor as lysozyme b ... | 1999 | 10377982 |
| new axonemal dynein heavy chains from tetrahymena thermophila. | two dyneins can be extracted from tetrahymena ciliary axonemes. the 22s dynein contains three heavy chains (hc), sediments at 22s in a sucrose gradient, and makes up the outer arms. the 14s dynein contains two to six hcs, sediments at 14s, and is thought to contribute to formation of the inner arms. we have identified two large proteins that are extracted from tetrahymena axonemes with high salt and that sediment together at approximately 18s. the two large proteins cleave when subjected to uv l ... | 2009 | 10361736 |
| affinity-purification of concanavalin a-binding ciliary glycoconjugates of starved and feeding tetrahymena thermophila. | development of mating competency in tetrahymena thermophila requires starvation for at least 70 min in low ionic strength buffer. pair formation between conjugating cells is blocked at early stages by the lectin concanavalin a (con a). to investigate the role of con a-binding proteins in this induced cellular change and pairing, and to confirm and extend an earlier study from our laboratory, a method was developed for preparation of con a-binding proteins from ciliary membrane-rich fractions of ... | 2003 | 10361735 |
| the telomerase rna pseudoknot is critical for the stable assembly of a catalytically active ribonucleoprotein. | telomerase is a ribonucleoprotein reverse transcriptase that synthesizes telomeric dna. a pseudoknot structure is phylogenetically conserved within the rna component of telomerase in all ciliated protozoans examined. here, we report that disruptions of the pseudoknot base pairing within the telomerase rna from tetrahymena thermophila prevent the stable assembly in vivo of an active telomerase. restoring the base-pairing potential of the pseudoknot by compensatory changes restores telomerase acti ... | 1999 | 10359761 |
| cultivation of tetrahymena thermophila in a 1.5-m3 airlift bioreactor. | a large-scale cultivation system for the mass cell production and extraction of the protozoon tetrahymena thermophila has been developed on the basis of a low-cost complex nutrient medium. cell growth and the production of extracellular proteases were investigated using a 15-l stirred-tank reactor and 13-l and 1500-l airlift reactors. processes using defined and complex medium formulations were compared. after cell mass production by 1200 l cell suspension in the large airlift bioreactor, two di ... | 1999 | 10341428 |
| identification and mutation of phosphorylation sites in a linker histone. phosphorylation of macronuclear h1 is not essential for viability in tetrahymena. | linker histone phosphorylation has been suggested to play roles in both chromosome condensation and transcriptional regulation. in the ciliated protozoan tetrahymena, in contrast to many eukaryotes, histone h1 of macronuclei is highly phosphorylated during interphase. macronuclei divide amitotically without overt chromosome condensation in this organism, suggesting that requirements for phosphorylation of macronuclear h1 may be limited to transcriptional regulation. here we report the major site ... | 1999 | 10329641 |
| a nonessential hp1-like protein affects starvation-induced assembly of condensed chromatin and gene expression in macronuclei of tetrahymena thermophila. | heterochromatin represents a specialized chromatin environment vital to both the repression and expression of certain eukaryotic genes. one of the best-studied heterochromatin-associated proteins is drosophila hp1. in this report, we have disrupted all somatic copies of the tetrahymena hhp1 gene, which encodes an hp1-like protein, hhp1p, in macronuclei (h. huang, e. a. wiley, r. c. lending, and c. d. allis, proc. natl. acad. sci. usa 95:13624-13629, 1998). unlike the drosophila hp1 gene, hhp1 is ... | 1999 | 10207086 |
| lysosomal glycerophosphocholine phosphodiesterase in tetrahymena. | the purification and characterization of a novel phosphodiesterase (pde) is presented. the activity was detected in the extracellular medium of tetrahymena thermophila cultures, by the release of p-nitrophenol from p-nitrophenylphosphocholine (pnppc) with an acidic ph optimum. in cell homogenates, it is sedimentable, shows a latency similar to that of acid phosphatase and is co-secreted with this enzyme, indicating that it is a lysosomal hydrolase. pnppc-pde was purified to homogeneity from the ... | 1999 | 10205674 |
| the conjusome: a novel structure in tetrahymena found only during sexual reorganization. | a unique structure, the conjusome, has been identified and initially characterized in tetrahymena thermophila. the conjusome appears only during a specific phase of conjugation. immunofluorescence microscopy reveals that the conjusome is strongly labeled by antibodies to the protein pdd1p. pdd1p is a chromodomain protein and participates in the formation of chromatin-containing structures in developing macronuclear anlagen. recent studies suggest that pdd1p is physically associated with the elim ... | 1999 | 10198282 |
| interface-mediated death of unconditioned tetrahymena cells: effect of the medium composition. | we have previously shown that the cell death of tetrahymena thermophila in low inocula cultures in a chemically-defined medium is not apoptotic. the death is caused by a cell lysis occurring at the medium-air interface and can be prevented by the addition of insulin or pluronic f-68. here, we report that cell death can also be caused by the medium. the specific effects of several medium constituents were tested in the presence and absence of an interface. four of the 19 amino acids (arginine, as ... | 2006 | 10188256 |
| gene knockouts reveal separate functions for two cytoplasmic dyneins in tetrahymena thermophila. | in many organisms, there are multiple isoforms of cytoplasmic dynein heavy chains, and division of labor among the isoforms would provide a mechanism to regulate dynein function. the targeted disruption of somatic genes in tetrahymena thermophila presents the opportunity to determine the contributions of individual dynein isoforms in a single cell that expresses multiple dynein heavy chain genes. substantial portions of two tetrahymena cytoplasmic dynein heavy chain genes were cloned, and their ... | 1999 | 10069817 |
| a method for the preparation of tetrahymena thermophila phospholipase a1 suitable for large-scale production. | a rapid and economical method for the purification of phospholipase a1 (pla1) from the extracellular medium of the ciliate tetrahymena thermophila is presented. essentially, the procedure, here designated as purification by selective interaction (psi), entails the incubation of media containing pla1 with liposomes made of soy bean phospholipids. the pla1-lipid complexes are precipitated by the addition of cacl2 and collected by centrifugation. elution of the pla1 is effected by treating the comp ... | 1999 | 10063621 |
| atp reception and chemosensory adaptation in tetrahymena thermophila. | micromolar concentrations of adenosine triphosphate (atp) and its non-hydrolyzable analog &bgr;- &ggr; -methylene atp are both effective depolarizing chemorepellents in tetrahymena thermophila. chemorepellent behavior consists of repeated bouts of backward swimming (avoidance reactions) that can easily be quantified to provide a convenient bioassay for purinergic reception studies. chemosensory adaptation occurs following prolonged exposure (10 min) to the repellents, and cells regain normal swi ... | 1999 | 9914148 |
| a preorganized active site in the crystal structure of the tetrahymena ribozyme. | group i introns possess a single active site that catalyzes the two sequential reactions of self-splicing. an rna comprising the two domains of the tetrahymena thermophila group i intron catalytic core retains activity, and the 5.0 angstrom crystal structure of this 247-nucleotide ribozyme is now described. close packing of the two domains forms a shallow cleft capable of binding the short helix that contains the 5' splice site. the helix that provides the binding site for the guanosine substrat ... | 1998 | 9841391 |
| maturation of phagosomes is accompanied by specific patterns of small gtpases. | in this study we purified phagosomes of the ciliated protozoan tetrahymena thermophila to analyze aspects of the maturation pathway of phagocytotic vesicles. phagosomes were labeled with magnetic microparticles and then purified in high amounts with the help of a permanent magnet. by combining a pulse-chase labeling protocol with the magnetic separation procedure we were able to isolate phagosomes of defined ages, which represent distinct stages of their maturation pathway. gtp-overlay assays sh ... | 1998 | 9820978 |
| abortive conjugation induced by uv-b irradiation at meiotic prophase in tetrahymena thermophila. | conjugating tetrahymena were irradiated by ultraviolet-b (uv-b) at various stages of conjugation. when the conjugants were exposed to the uv-b at late meiotic prophase (the stage from pachytene to diplotene), abortive conjugation was induced a high frequencies. after completing meiosis, a significant number of the conjugants showed marked anomalies, i.e., failure of nuclear selection after meiosis, and abortion of the subsequent conjugation process such as a postmeiotic division to form gametic ... | 1998 | 9770271 |
| tetrahymena mutants with short telomeres. | telomere length is dynamic in many organisms. genetic screens that identify mutants with altered telomere lengths are essential if we are to understand how telomere length is regulated in vivo. in tetrahymena thermophila, telomeres become long at 30 degrees, and growth rate slows. a slow-growing culture with long telomeres is often overgrown by a variant cell type with short telomeres and a rapid-doubling rate. here we show that this variant cell type with short telomeres is in fact a mutant wit ... | 1998 | 9755196 |
| rna folding causes secondary structure rearrangement. | the secondary structure of the p5abc subdomain (a 56-nt rna) of the tetrahymena thermophila group i intron ribozyme has been determined by nmr. its base pairing in aqueous solution in the absence of magnesium ions is significantly different from the rna in a crystal but is consistent with thermodynamic predictions. on addition of magnesium ions, the rna folds into a tertiary structure with greatly changed base pairing consistent with the crystal structure: three watson-crick base pairs, three g. ... | 1998 | 9751704 |
| a practical assay of lipoate in biologic fluids and liver in health and disease. | a procedure for assaying lipoic acid concentration in biologic fluids and tissues was devised using a eukaryotic protozoan tetrahymena thermophila. t.thermophila has a specific and sensitive (30 pg/ml) requirement for lipoic acid. unlike humans and other microorganisms, t.thermophila can not synthesize lipoic acid; hence, its requirement for exogenous lipoic acid is specific. the lipoic acid supplied to t. thermophila by the processing of biologic fluids and tissues during the assay procedure, p ... | 1998 | 9741583 |
| folding intermediates of a self-splicing rna: mispairing of the catalytic core. | the tetrahymena thermophila self-splicing rna is trapped in an inactive conformation during folding reactions at physiological temperatures. the structure of this metastable intermediate was probed by chemical modification interference and site-directed mutagenesis. in the inactive structure, an incorrect base-pairing, which we call alt p3, displaces the p3 helix in the catalytic core of the intron. mutations that stabilize alt p3 increase the fraction of pre-rrna that becomes trapped in the ina ... | 1998 | 9677291 |
| telomerase reverse transcriptase genes identified in tetrahymena thermophila and oxytricha trifallax. | telomerase reverse transcriptase (tert) has been identified as the catalytic subunit of the chromosome end-replicating enzyme in euplotes, yeasts, and mammals. however, it was not reported among the protein components of purified tetrahymena telomerase, the first telomerase identified and the most thoroughly studied. it therefore seemed possible that tetrahymena used an alternative telomerase that lacked a tert protein. we now report the cloning and sequencing of a tetrahymena thermophila gene w ... | 1998 | 9671703 |
| two types of telomeric chromatin in tetrahymena thermophila. | the telomeric d(ggggtt).d(aacccc) repeat tracts (g4t2 repeats) in tetrahymena thermophila macronuclei were shown previously to be packaged in a non-nucleosomal dna-protein complex. here, we demonstrate that these telomeric repeats, together with a short region of the immediately adjacent non-telomeric sequence, exist in two distinct types of chromatin. the non-nucleosomal complex (type i complex) comprises approximately 90 to 97% of telomeric dna, has no apparent underlying periodic nucleosomal ... | 1998 | 9665840 |
| proposed genetic nomenclature rules for tetrahymena thermophila, paramecium primaurelia and paramecium tetraurelia. the seventh international meeting on ciliate molecular biology genetics nomenclature. | | 1998 | 9660671 |
| phosphorylation of histone h3 at serine 10 is correlated with chromosome condensation during mitosis and meiosis in tetrahymena. | h3 phosphorylation has been correlated with mitosis temporally in mammalian cells and spatially in ciliated protozoa. in logarithmically growing tetrahymena thermophila cells, for example, h3 phosphorylation can be detected in germline micronuclei that divide mitotically but not in somatic macronuclei that divide amitotically. here, we demonstrate that micronuclear h3 phosphorylation occurs at a single site (ser-10) in the amino-terminal domain of histone h3, the same site phosphorylated during ... | 1998 | 9636175 |
| a pcr screen identifies a novel, unconventional myosin heavy chain gene (myo1) in tetrahymena thermophila. | degenerate primers for two regions of sequence homology in the myosin head domain were used in a polymerase chain reaction screen of tetrahymena thermophila genomic dna to amplify a 765 bp fragment that was cloned and sequenced. based on the presence of conserved, myosin-specific sequences, the 765 bp pcr product was identified as a fragment of a myosin gene, the first to be discovered in ciliated protozoa and herein referred to as myo1. an inverse polymerase chain reaction strategy was used to ... | 2013 | 9627986 |
| an intragenic suppressor of cold sensitivity identifies potentially interacting bases in the peptidyl transferase center of tetrahymena rrna. | peptidyl transfer of a growing peptide on a ribosome-bound transfer rna (trna) to an incoming amino acyl trna is the central step in translation, and it may be catalyzed primarily by the large subunit (lsu) ribosomal rna (rrna). genetic and biochemical evidence suggests that the central loop of domain v of the lsu rrna plays a direct role in peptidyl transfer. it was previously found that a single base change at a universally conserved site in this region of the tetrahymena thermophila lsu rrna ... | 1998 | 9611204 |
| autocrine/paracrine activator of cell proliferation: purification of a 4-6 kd compound with growth-factor-like effects in tetrahymena thermophila. | extracellular medium from cultures of tetrahymena thermophila was collected, concentrated and fractionated by ultrafiltration and low-pressure column chromatography. the effect on proliferation of various fractions was tested on cultures of t. thermophila in synthetic medium at low initial cell densities (< 250 cells/ml). in unsupplemented cultures, cells failed to thrive and died before proliferation. addition of the fraction isolated from the extracellular medium in the molecular weight range ... | 1998 | 9617475 |
| purification, characterization and molecular cloning of tgp1, a novel g-dna binding protein from tetrahymena thermophila. | g-dna, a polymorphic family of four-stranded dna structures, has been proposed to play roles in a variety of biological processes including telomere function, meiotic recombination and gene regulation. here we report the purification and cloning of tgp1, a g-dna specific binding protein from tetrahymena thermophila. tgp1 was purified by three-column chromatographies, including a g-dna affinity column. two major proteins (approximately 80 and approximately 40 kda) were present in the most highly ... | 1998 | 9512530 |
| a promoter region mutation affecting replication of the tetrahymena ribosomal dna minichromosome. | in the ciliated protozoan tetrahymena thermophila the ribosomal dna (rdna) minichromosome replicates partially under cell cycle control and is also subject to a copy number control mechanism. the relationship between rdna replication and rrna gene transcription was investigated by the analysis of replication, transcription, and dna-protein interactions in a mutant rdna, the rmm3 rdna. the rmm3 (for rdna maturation or maintenance mutant 3) rdna contains a single-base deletion in the rrna promoter ... | 1998 | 9566921 |
| a developmentally eliminated sequence in the flanking region of the histone h1 gene in tetrahymena thermophila contains short repeats. | in tetrahymena, as in other ciliated protozoans, a transcriptionally active, 'somatic' macronucleus develops from a transcriptionally inactive 'germline' micronucleus after conjugation. the process of development involves elimination of germline dna segments at thousands of locations in the genome. the characterization of one of these segments in tetrahymena thermophila is described here. this micronucleus-specific dna has been identified by comparing the sequence of the corresponding micronucle ... | 2007 | 9561773 |
| proteolytic processing and ca2+-binding activity of dense-core vesicle polypeptides in tetrahymena. | formation and discharge of dense-core secretory vesicles depend on controlled rearrangement of the core proteins during their assembly and dispersal. the ciliate tetrahymena thermophila offers a simple system in which the mechanisms may be studied. here we show that most of the core consists of a set of polypeptides derived proteolytically from five precursors. these share little overall amino acid identity but are nonetheless predicted to have structural similarity. in addition, sites of proteo ... | 1998 | 9450970 |
| purification and characterization of a novel chemorepellent receptor from tetrahymena thermophila. | chemosensory transduction and adaptation are important aspects of signal transduction mechanisms in many cell types, ranging from prokaryotes to differentiated tissues such as neurons. the eukaryotic ciliated protozoan, tetrahymena thermophila, is capable of responding to both chemoattractants (o'neill et al., 1985; leick, 1992; kohidai, karsa & csaba, 1994, 1995) and chemorepellents (francis & hennessey, 1995; kuruvilla, kim & hennessey, 1997). an example of a nontoxic, depolarizing chemorepell ... | 1998 | 9516237 |
| experimental evolution of complexity: in vitro emergence of intermolecular ribozyme interactions. | in the course of evolving variants of the tetrahymena thermophila group i ribozyme for improved dna cleavage in vitro, we witnessed the unexpected emergence of a derived molecular species, capable of acting as a partner for the ribozyme, but no longer autocatalytic. this new rna species exhibits a deletion in the catalytic core and participates in a productive intermolecular interaction with an active ribozyme, thus insuring its survival in the population. these novel rna molecules have evolved ... | 1998 | 9510329 |
| physical characterization and atpase activity of 14s dynein fractions from tetrahymena thermophila. | using anion-exchange fast protein liquid chromatography, 14s dynein was separated into four fractions (designated 1-4). these fractions were distinguished with respect to polypeptide composition, and at least four unique heavy chains were identified. each fraction was shown to exhibit atpase activity. fraction 2 has a specific activity 2-3 times greater than that of fractions 1, 3, and 4; the fractions showed a consistent trend of decreasing activity in the order 2 > 3 > 1 > 4. in all cases, the ... | 1997 | 9429162 |
| regulatory sequences for the amplification and replication of the ribosomal dna minichromosome in tetrahymena thermophila. | we have analyzed the cis-acting sequences that regulate rrna gene (rdna) replication in tetrahymena thermophila. the macronucleus of this ciliated protozoan contains 9,000 copies of a 21-kbp minichromosome in the form of a palindrome comprising two copies of the rdna. these are derived from a single chromosomally integrated copy during conjugation through selective amplification and are maintained by replicating once per cell cycle during vegetative growth. we have developed a transformation vec ... | 1997 | 9372956 |
| constitutive expression, not a particular primary sequence, is the important feature of the h3 replacement variant hv2 in tetrahymena thermophila. | although quantitatively minor replication-independent (replacement) histone variants have been found in a wide variety of organisms, their functions remain unknown. like the h3.3 replacement variants of vertebrates, hv2, an h3 variant in the ciliated protozoan tetrahymena thermophila, is synthesized and deposited in nuclei of nongrowing cells. although hv2 is clearly an h3.3-like replacement variant by its expression, sequence analysis indicates that it evolved independently of the h3.3 variants ... | 1997 | 9343391 |
| the trnatyr-isoacceptors and their genes in the ciliate tetrahymena thermophila: cytoplasmic trnatyr has a qpsia anticodon and is coded by multiple intron-containing genes. | in the ciliated protozoa tetrahymena thermophila introns have been detected in rrna and mrnas until now. we have isolated and sequenced seven trnatyr genes from the t.thermophila nuclear genome. all of these genes contain introns of identical length and sequence. the 11 bp long intervening sequences are located 1 nt 3' to the anticodon as found in other eukaryotic nuclear trna genes. tetrahymena trnatyr genes are efficiently transcribed in hela cell nuclear extract. moreover, processing and spli ... | 1997 | 9336446 |
| analysis of exocytosis mutants indicates close coupling between regulated secretion and transcription activation in tetrahymena. | stimulation of regulated secretory cells promotes protein release via the fusion of cytoplasmic storage vesicles with the plasma membrane. in tetrahymena thermophila, brief exposure to secretagogue results in synchronous fusion of the entire set of docked dense-core granules with the plasma membrane. we show that stimulation is followed by rapid new dense-core granule synthesis involving gene induction. two genes encoding granule matrix proteins, grl1 and grl4, are shown to undergo induction fol ... | 1997 | 9380694 |
| alternate junctions and microheterogeneity of tlr1, a developmentally regulated dna rearrangement in tetrahymena thermophila. | a large number of developmentally regulated dna rearrangements occur during the development of the macronucleus in tetrahymena thermophila. tlr1 is a deletion element which has large inverted repeats near the rearrangement junctions and deletes more than 13 kbp of internal dna. previous analysis of caryonidal lines revealed alternate left junctions for the tlr1 rearrangement in b strain cells. we show here that c2 strain tetrahymena also use alternate rearrangement junctions. we have mapped and ... | 2008 | 9304822 |
| cloning and sequencing of a cdna encoding glyceraldehyde-3-phosphate dehydrogenase from tetrahymena thermophila: growth-associated changes in its mrna expression. | glyceraldehyde-3-phosphate dehydrogenase is a key enzyme in the glycolytic pathway. since its transcript levels do not vary in most experimental conditions, it has been often used as a control in northern blot or reverse transcriptase-polymerase chain reaction analysis. we have cloned and sequenced a gene encoding glyceraldehyde-3-phosphate dehydrogenase (tthgapdh) from tetrahymena thermophila cdna library and determined whether the tthgapdh mrna is a loading control in gene expression studies o ... | 2005 | 9304812 |
| a mutational analysis of conjugation in tetrahymena thermophila. 2. phenotypes affecting middle and late development: third prezygotic nuclear division, pronuclear exchange, pronuclear fusion, and postzygotic development. | conjugation following pair formation in tetrahymena can be divided into three distinct sequences of events: prezygotic development, postzygotic development, and exconjugant development. the decision to proceed with postzygotic development is governed by a developmental checkpoint occurring sometime during the middle stages of conjugation. a second developmental decision is made to initiate pair separation and exconjugant development. this paper examines the phenotypes of five newly isolated conj ... | 1997 | 9299116 |
| a mutational analysis of conjugation in tetrahymena thermophila. 1. phenotypes affecting early development: meiosis to nuclear selection. | conjugation in the freshwater ciliate tetrahymena thermophila involves a developmental program that models meiosis, fertilization, and early developmental events characteristic of multicellular eukaryotes. we describe a gallery of five early-acting conjugation mutations. these mutants, cnj1-5, exhibit phenotypes in which specific steps in the conjugal pathway have been altered or eliminated. specifically, cnj1 and cnj2 fail to condense their micronuclear chromatin prior to each of the three prez ... | 1997 | 9299115 |
| a second catalytic metal ion in group i ribozyme. | although only a subset of protein enzymes depend on the presence of a metal ion for their catalytic function, all naturally occurring rna enzymes require metal ions to stabilize their structure and for catalytic competence. in the self-splicing group i intron from tetrahymena thermophila, several divalent metals can serve structural roles, but only mg2+ and mn2+ promote splice-site cleavage and exon ligation. a study of a ribozyme reaction analogous to 5'-splice-site cleavage by guanosine uncove ... | 1997 | 9285596 |
| the intranuclear organization of normal, hemizygous and excision-deficient rrna genes during developmental amplification in tetrahymena thermophila. | in the ciliated protozoan, tetrahymena thermophila, the diploid germinal micronucleus contains two allelic copies of the gene for ribosomal rna (rdna). during genesis of new somatic macronuclei the germline rdna gene is excised by developmentally programmed chromosome breakage and preferentially amplified to approximately 9, 000 copies. we have studied this process by fluorescence in situ hybridization. we find that initially rdna amplification is restricted to two separate and highly confined r ... | 1997 | 9254725 |
| solution conformation of a five-nucleotide rna bulge loop from a group i intron. | we present the solution conformation, determined by nmr spectroscopy, of a five-nucleotide rna bulge loop. the bulge interrupts the stem of a 25-nucleotide rna hairpin, and its sequence and flanking sequences are those of a conserved bulge from a group i intron. the secondary structure of the bulge loop in the hairpin context is that predicted by the secondary structure prediction algorithm of zuker. it differs, however, from the secondary structure deduced from sequence covariation of the bulge ... | 1997 | 9254623 |
| effects of divalent metal ions on individual steps of the tetrahymena ribozyme reaction. | the tetrahymena thermophila l-21 scai ribozyme utilizes mg2+ to catalyze a site-specific endonuclease reaction analogous to the first step of self-splicing. to better understand the contribution of mg2+ to ribozyme activity, the mg2+ concentration dependence of individual rate constants was examined at concentrations greater than those required for ribozyme folding (>2 mm; at 50 degrees c and ph 6.7). analysis of metal ion inhibition of the chemical step of the reaction indicated that two ca2+ i ... | 1997 | 9204875 |
| germline and somatic transformation of mating tetrahymena thermophila by particle bombardment. | mating tetrahymena thermophila were bombarded with ribosomal dna-coated particles at various times in development. both macronuclear and micronuclear transformants were recovered. optimal developmental stages for transformation occurred during meiosis for the micronucleus and during anlagen formation for the macronucleus. evidence is given for transient retention of the introduced plasmid. genetic and molecular tests confirmed that sexually heritable transformation was associated with integratio ... | 1997 | 9136007 |
| a rapid bioassay to detect mycotoxins using a melanin precursor overproducer mutant of the ciliate tetrahymena thermophila. | four different mycotoxins (patulin, t-2 toxin, diacetoxyscirpenol and roquefortine) were used to study growth inhibitory effects on a melanin precursor overproducer mutant of the ciliate tetrahymena thermophila. this strain is especially sensitive to diacetoxyscirpenol and t-2 toxin. the secretion capacity of melanin precursors into the culture medium by this mutant and its biosensor capacity are very useful characteristics to elaborate a rapid bioassay to detect some specific mycotoxins. | 1997 | 9204533 |
| a functional telomerase rna swap in vivo reveals the importance of nontemplate rna domains. | the ribonucleoprotein (rnp) enzyme telomerase is required for replication of eukaryotic chromosomal termini. the rna moiety of telomerase is essential for enzyme function and provides the template for telomeric dna synthesis. however, the roles of its nontemplate domains have not been explored. here we demonstrate that a novel interspecies telomerase rna swap in vivo creates a functional but aberrant telomerase. telomerase rna from the ciliate glaucoma chattoni was expressed in tetrahymena therm ... | 1997 | 9096304 |
| block in anaphase chromosome separation caused by a telomerase template mutation. | telomeres are essential for chromosome stability, but their functions at specific cell-cycle stages are unknown. telomeres are now shown to have a role in chromosome separation during mitosis. in telomeric dna mutants of tetrahymena thermophila, created by expression of a telomerase rna with an altered template sequence, division of the germline nucleus was severely delayed or blocked in anaphase. the mutant chromatids failed to separate completely at the midzone, becoming stretched to up to twi ... | 1997 | 9045613 |
| germ-line knockout heterokaryons of an essential alpha-tubulin gene enable high-frequency gene replacement and a test of gene transfer from somatic to germ-line nuclei in tetrahymena thermophila. | the haploid tetrahymena thermophila genome contains a single alpha-tubulin (atu) gene. using biolistic transformation, we disrupted one of the two copies of the atu gene in the diploid germ-line micronucleus. the heterozygous germ-line transformants were made homozygous in the micronucleus by mating to a star strain containing a defective micronucleus. this mating, known as round 1 genomic exclusion, resulted in two heterokaryon clones of different mating types which have both copies of the atu ... | 1997 | 9037049 |
| phosphorylation of linker histones by a protein kinase a-like activity in mitotic nuclei. | micronuclear linker histones of the ciliated protozoan, tetrahymena thermophila, are extensively phosphorylated in vivo. each of these polypeptides, alpha, beta, gamma, and delta, contains sites for phosphorylation by cyclic-amp dependent protein kinase (pka) but not cdc2 kinase, and some data have been presented implicating pka kinase in their phosphorylation in vitro and in vivo (sweet, m. t., and allis, c. d. (1993) chromosoma 102, 637-647; sweet, m. t., jones, k., and allis, c. d. (1996) j. ... | 1997 | 8995382 |
| phosphorylation of a 70 kd tetrahymena ciliary membrane protein is associated with ciliogenesis. | to identify proteins in tetrahymena thermophila which were phosphorylated during ciliary assembly, the antiphosphoprotein antibody mpm-2 was used to probe blots of total ciliary protein or axonemal and ciliary membrane/matrix fractions from full-length cilia, regenerating cilia, or cilia that had grown to full-length following deciliation. a 70 kd protein was recognized by mpm-2 only in blots of total ciliary protein from regenerating cilia and of the membrane/matrix fraction from regenerating c ... | 1997 | 9670473 |
| effects of protein kinase c activators and staurosporine on protein kinase activity, cell survival, and proliferation in tetrahymena thermophila. | autocrine factors prevent cell death in the ciliate tetrahymena thermophila, a unicellular eukaryote, in a chemically defined medium. at certain growth conditions these factors are released at a sufficient concentration by > 500 cells ml-1 to support cell survival and proliferation. the protein kinase c activators phorbol 12-myristate 13-acetate (pma) or 1-oleyl 2-acetate glycerol (oag) when added to 250 cells ml-1 supported cell survival and proliferation. in the presence of the serine and thre ... | 1997 | 9523425 |
| new loop-loop tertiary interactions in self-splicing introns of subgroup ic and id: a complete 3d model of the tetrahymena thermophila ribozyme. | group i introns self-splice via two consecutive trans-esterification reactions in the presence of guanosine cofactor and magnesium ions. comparative sequence analysis has established that a catalytic core of about 120 nucleotides is conserved in all known group i introns. this core is generally not sufficient for activity, however, and most self-splicing group i introns require non-conserved peripheral elements to stabilize the complete three-dimensional (3d) structure. the physico-chemical prop ... | 1996 | 9000010 |
| mapping three classical isozyme loci in tetrahymena: meiotic linkage of esta to the chxa linkage group. | we demonstrate a reliable method for mapping conventional loci and obtaining meiotic linkage data for the ciliated protozoan tetrahymena thermophila. by coupling nullisomic deletion mapping with meiotic linkage mapping, loci known to be located on a particular chromosome or chromosome arm can be tested for recombination. this approach has been used to map three isozyme loci, esta (esterase a), estb (esterase b), and acpa (acid phosphatase a), with respect to the chxa locus (cycloheximide resista ... | 1996 | 8978038 |
| investigation of the structural basis for thermodynamic stabilities of tandem gu mismatches: solution structure of (rgaggucuc)2 by two-dimensional nmr and simulated annealing. | the duplex (rgaggucuc)2 contains the motif [sequence: see text] which is unusually stable compared with other symmetric tandem gu mismatches and occurs in the p5 helix of the group i intron of tetrahymena thermophila. the three-dimensional solution structure of (rgaggucuc)2 was determined using two-dimensional nmr and a simulated annealing protocol. the structure is remarkably similar to the a-dna crystal structure of (dggggtccc)2 [kneale, g., brown, t., & kennard, o. (1985) j. mol. biol. 186, 8 ... | 1996 | 8916893 |
| metal-binding sites in the major groove of a large ribozyme domain. | group i self-splicing introns catalyze sequential transesterification reactions within an rna transcript to produce the correctly spliced product. often several hundred nucleotides in size, these ribozymes fold into specific three-dimensional structures that confer activity. the 2.8 a crystal structure of a central component of the tetrahymena thermophila group i intron, the 160-nucleotide p4-p6 domain, provides the first detailed view of metal binding in an rna large enough to exhibit side-by-s ... | 1996 | 8939748 |
| an engineered tetrahymena trnagln for in vivo incorporation of unnatural amino acids into proteins by nonsense suppression. | a new trna, thg73, has been designed and evaluated as a vehicle for incorporating unnatural amino acids site-specifically into proteins expressed in vivo using the stop codon suppression technique. the construct is a modification of trnagln(cua) from tetrahymena thermophila, which naturally recognizes the stop codon uag. using electrophysiological studies of mutations at several sites of the nicotinic acetylcholine receptor, it is established that thg73 represents a major improvement over previo ... | 1996 | 8798511 |
| crystal structure of a group i ribozyme domain: principles of rna packing. | group i self-splicing introns catalyze their own excision from precursor rnas by way of a two-step transesterification reaction. the catalytic core of these ribozymes is formed by two structural domains. the 2.8-angstrom crystal structure of one of these, the p4-p6 domain of the tetrahymena thermophila intron, is described. in the 160-nucleotide domain, a sharp bend allows stacked helices of the conserved core to pack alongside helices of an adjacent region. two specific long-range interactions ... | 1996 | 8781224 |
| sequence effects on rna bulge-induced helix bending and a conserved five-nucleotide bulge from the group i introns. | bulge loops introduce bends in rna double helices. thus, a role for bulge loops in the tertiary folding of rna is to orient helical elements. the location, size, and sequence of a five-nucleotide bulge are conserved in many of the self-splicing group i introns. we have used gel electrophoretic analysis of helix bending to test the hypothesis that this bulge loop is conserved to control the angle between the flanking helices. interruption of an rna duplex by the five-nucleotide bulge of the group ... | 1996 | 8794748 |
| mutations in the tetrahymena ribozyme internal guide sequence: effects on docking of the p1 helix into the catalytic core and correlation with catalytic activity. | binding of substrate by the ribozyme derived from the self-splicing intron of tetrahymena thermophila involves at least two steps. in the first step, base pairing between the ribozyme internal guide sequence (igs) and the substrate forms a helical duplex (p1). through specific tertiary interactions between p1 and the ribozyme core, p1 is then docked into the ribozyme active site. we have investigated the effects of compensatory mutations in positions 2-6 of the p1 helix on docking of p1 into the ... | 1996 | 8784205 |
| induction of blocks in nuclear divisions and overcondensation of meiotic chromosomes with cycloheximide during conjugation of tetrahymena thermophila. | during conjugation, the micronucleus of tetrahymena thermophila undergoes five consecutive nuclear divisions: meiosis, third prezygotic division (pregamic mitosis) and two postzygotic mitoses of the synkaryon. the four products of the synkaryon differentiate into macronuclear anlagen and new micronuclei and the old macronucleus is resorbed. the protein synthesis inhibitor cycloheximide, applied during conjugation, induced several developmental blocks. pairs shifted to the drug during early meiot ... | 2013 | 8822808 |
| linker histone h1 regulates specific gene expression but not global transcription in vivo. | in a linker histone h1 knockout strain (delta h1) of tetrahymena thermophila, the number of mature rnas produced by genes transcribed by pol i and pol iii and of most genes transcribed by pol ii remains unchanged. however, h1 is required for the normal basal repression of a gene (ngoa) in growing cells but is not required for its activated expression in starved cells. surprisingly, h1 is required for the activated expression of another gene (cyp) in starved cells but not for its repression in gr ... | 1996 | 8756729 |
| tetrahymena nuclear proteins that bind to a micronucleus-specific sequence during vegetative growth. | tetrahymena thermophila has two nuclei: a micronucleus is transcriptionally silent during vegetative growth and a macronucleus is active. extensive programmed dna rearrangement is known to occur during the development of the somatic macronucleus from the germ-line micronucleus. we previously found a 1.4 kb micronucleus-specific sequence, c-element, which was located upstream of the micronuclear calmodulin gene and was eliminated from the macronuclear genome during macronuclear development. here, ... | 1996 | 8940907 |
| ribonuclease p of tetrahymena thermophila. | ribonuclease p (rnase p) is responsible for the generation of mature 5' termini of trna. the rna component of this complex encodes the enzymatic activity in bacteria and is itself catalytically active under appropriate conditions in vitro. the role of the subunits in eucaryotes has not yet been established. we have partially purified rnase p activity from the ciliate protozoan tetrahymena thermophila to learn more about the biochemical characteristics of rnase p from a lower eucaryote. the tetra ... | 1996 | 8663280 |
| mitochondrial import of only one of three nuclear-encoded glutamine trnas in tetrahymena thermophila. | the mitochondrial genome of tetrahymena does not appear to encode enough trnas to perform mitochondrial protein synthesis. it has therefore been proposed that nuclear-encoded trnas are imported into the mitochondria. t.thermophila has three major glutamine trnas: trna(gln)(uug), trna(gln)(uua) and trna(gln)(cua). each of these trnas functions in cytosolic translation. however, due to differences between the tetrahymena nuclear and mitochondrial genetic codes, only trna(gln)(uug) has the capacity ... | 1996 | 8670829 |
| non-mendelian, heritable blocks to dna rearrangement are induced by loading the somatic nucleus of tetrahymena thermophila with germ line-limited dna. | site-specific dna deletion occurs at thousands of sites within the genome during macronuclear development of tetrahymena thermophila. these deletion elements are usually not detected in macronuclear chromosomes. we have interfered with the normal deletion of two of these elements, the adjacent m and r elements, by loading vegetative macronuclei with these elements prior to sexual conjugation. transformed cell lines containing the exogenous m or r element, carried on high-copy-number vectors cont ... | 1996 | 8668182 |
| developmentally programmed dna deletion in tetrahymena thermophila by a transposition-like reaction pathway. | we provide a molecular description of key intermediates in the deletion of two internal eliminated sequences (ies elements), the m and r regions, during macronuclear development in tetrahymena thermophila. using a variety of pcr-based methods in vivo, double-strand breaks are detected that are generated by hydrolytic cleavage and correspond closely to the observed chromosomal junctions left behind in the macronuclei. the breaks exhibit a temporal and structural relationship to the deletion react ... | 1996 | 8654384 |
| identification, mapping and linkage analysis of randomly amplified dna polymorphisms in tetrahymena thermophila. | using the random amplified polymorphic dna (rapd) technique and exploiting the unique genetics of tetrahymena thermophila, we have identified and characterized 40 dna polymorphisms occurring between two inbred strains (b and c3) of this ciliated protozoan. these rapd markers permit the pcr amplification of a dna species using template dna from sb1969 (b strain) but fail to do so using dna from c3-368-5 (c3 strain). polymorphisms were mapped to chromosomes using a panel of monosomic strains const ... | 1996 | 8725229 |
| programmed dna rearrangement from an intron during nuclear development in tetrahymena thermophila: molecular analysis and identification of potential cis-acting sequences. | during macronuclear development in the ciliate tetrahymena thermophila, extensive rearrangement events occur as dna deletions. we have studied a developmentally programmed deletion called mse2.9 that occurs within an intron in a gene in both genomic dna and in an rdna vector introduced into the cell by transformation. extensive microheterogeneity at the deletion junctions has been found in caryonidal strains and in the rdna in transformed cells. a transformation assay has been used to identify s ... | 1996 | 8657578 |
| an improved method to obtain high molecular weight dna from purified micro- and macronuclei of tetrahymena thermophila. | an improved method to obtain high molecular weight dna from purified macro- and micronuclei of tetrahymena thermophila is described. micro- and macronuclear dna obtained using previously described protocols was degraded and not suitable for the cloning of large (>100 kb) dna fragments. based on the data reported here, we propose that dna degradation is mainly due to nuclease activity; some micronuclear dna degradation is due to mechanical shearing as a result of extended periods of blending. we ... | 2013 | 8640190 |
| a voltage-dependent chloride channel from tetrahymena ciliary membrane incorporated into planar lipid bilayers. | membrane vesicles from cilia of tetrahymena thermophila were incorporated into a planar phospholipid bilayer membrane, and single-channel currents across the planar membrane were recorded under voltage-clamp conditions. a novel and reproducible chloride channel was observed when a mixture of phosphatidylethanolamine and phosphatidylcholine was used to form the planar lipid membrane but not when acidic phospholipid mixtures such as asolectin or a mixture containing phosphatidylserine. using symme ... | 1996 | 8639695 |
| new telomere formation coupled with site-specific chromosome breakage in tetrahymena thermophila. | programmed chromosome breakage occurs in many ciliated protozoa and is accompanied by efficient new telomere formation. in this study, we have investigated the relationship between programmed chromosome breakage and telomere formation in tetrahymena thermophila. using specially constructed dna clones containing the breakage signal cbs in transformation studies, we have determined the locations of telomere addition around the breakage sites. they occur at variable positions, over 90% of which are ... | 1996 | 8622671 |
| ph dependencies of the tetrahymena ribozyme reveal an unconventional origin of an apparent pka. | the l-21 scai ribozyme derived from the tetrahymena thermophila pre-rrna group i intron catalyzes a site-specific endonucleolytic cleavage of rna, dna, and chimeric rna/dna oligonucleotides: cccucua5 + g-->cccucu + ga5. the ph-rate dependence was determined for the reaction of the e.g complex with the oligonucleotide substrate d(cccuc)r(u)d(a5) [(kcat/km)s conditions]. although it was shown that the ph dependence is not affected by specific buffers, there is inhibition by specific monovalent cat ... | 1996 | 8634287 |
| involvement of active cellular mechanisms on the disorganization of oral apparatus in amicronucleate cells in tetrahymena thermophila. | ciliated protozoa, a group of unicellular eukaryotes, have two kinds of nuclei, a macronucleus (somatic nucleus) and a micronucleus (germinal nucleus) in a single cell. we previously reported that amicronucleate cells of tetrahymena thermophila induced by nocodazole gradually lost their oral apparatus (oa) and ciliary rows but that amacronucleate cells did not. since the macronucleus is responsible for the gene expression in the vegetative phase, the effects of actinomycin d and cycloheximide on ... | 1996 | 8726476 |
| tetrahymena thermophila: analysis of phospholipids and phosphonolipids by high-field 1h-nmr. | the phospholipids of control and lipid-modified tetrahymena thermophila were identified and quantified, using 1-d and 2-d cosy proton nmr spectroscopy on intact lipids, before and after hplc separation. the results are comparable to those obtained using classical lipid analytical techniques. the results indicate that the study of enzyme pathways and other metabolic processes involving phospholipids in tetrahymena and related protozoa can be carried out using proton nmr spectroscopy as the invest ... | 1996 | 8555261 |
| a mechanistic framework for the second step of splicing catalyzed by the tetrahymena ribozyme. | a simple model system is described which mimics the second step of splicing and reverse cyclization reactions of the self-splicing intron from tetrahymena thermophila. this model is based on the l-21 sca i catalyzed ligation reaction between exogenously added oligomers: cucu + ucga l-21 sca i cucua + ucg. steady-state kinetics for the forward and reverse direction were measured at 15 degrees c to find oligonucleotides that exhibit michaelis-menten behavior with acceptable kms. cucu and ucga fit ... | 1996 | 8555239 |
| effects of the transcription inhibitor actinomycin d on postzygotic development of tetrahymena thermophila conjugants. | during tetrahymena thermophila conjugation, new somatic macronuclei develop from a common zygotic nucleus derived from meiotic products of the germline, and the old parental somatic nucleus is destroyed. the transcription inhibitor actinomycin d disrupts many events of postzygotic conjugation (cycloheximide causes indistinguishable effects). early treatment causes a block of all postzygotic development, suggesting a transcription requirement for conjugants to pass a checkpoint, allowing entry in ... | 1996 | 8575619 |
| genome downsizing during ciliate development: nuclear division of labor through chromosome restructuring. | the ciliated protozoa divide the labor of germline and somatic genetic functions between two distinct nuclei. the development of the somatic (macro-) nucleus from the germinal (micro-) nucleus occurs during sexual reproduction and involves large-scale, genetic reorganization including site-specific chromosome breakage and dna deletion. this intriguing process has been extensively studied in tetrahymena thermophila. characterization of cis-acting sequences, putative protein factors, and possible ... | 1996 | 8982465 |
| recent progress in understanding the temporal behavior of unicellular organisms. | this survey summarizes the findings concerning endogenous oscillations of three unicellular organisms: the dinophyte gonyaulax polyedra, the ciliate tetrahymena thermophila and the euglenophyte euglena gracilis. all of them behave rhythmically and show the common features of zeitgeber action, differential sensitivity and temperature compensation; however, they exhibit some species-specific peculiarities that make each of them suitable for addressing particular chronobiological questions. althoug ... | 1996 | 8731337 |