| rev/rre-independent mason-pfizer monkey virus constitutive transport element-dependent propagation of sivmac239 vectors using a single round of replication assay. | in a step toward creating live-attenuated or dna subunit vaccines for aids, the replication of simian immunodeficiency virus (siv) was studied independently of the rev and rre (rev-responsive element) regulatory system, over a single round. to accomplish this, the env gene of an siv vector was made defective by the insertion of a sv40 promoter/enhancer hygromycin b phosphotransferase gene cassette. using this vector as the backbone, molecular clones of siv were generated that contained a mutated ... | 1996 | 8806531 |
| role of mason-pfizer monkey virus (mpmv) constitutive transport element (cte) in the propagation of mpmv vectors by genetic complementation using homologous/heterologous env genes. | to study mason-pfizer monkey virus (mpmv) replication over a single round, virus particles were generated that contain a replication-defective vector encoding a dominant selectable marker, the hygromycin b phosphotransferase (hyg) gene. genetic complementation with a homologous mpmv envelope glycoprotein (env-gp) or pseudotyping by several heterologous env-gps from a variety of viruses resulted in infectious mpmv particles containing the replication-defective rna. recently, it has been shown tha ... | 1996 | 8874512 |
| a structured retroviral rna element that mediates nucleocytoplasmic export of intron-containing rna. | a common feature of gene expression in all retroviruses is that unspliced, intron-containing rna is exported to the cytoplasm despite the fact that cellular rnas which contain introns are usually restricted to the nucleus. in complex retroviruses, the export of intron-containing rna is mediated by specific viral regulatory proteins (e.g., human immunodeficiency virus type 1 [hiv-1] rev) that bind to elements in the viral rna. however, simpler retroviruses do not encode such regulatory proteins. ... | 1997 | 8972193 |
| characterization of enzootic nasal tumor virus capsid antigen. | the rt-pcr was carried out on tumor tissue from sheep with enzootic nasal tumor (ent), using primers designed from conserved amino acid regions of related type d retroviruses. a 591 bp pcr fragment, corresponding to 90% of the capsid antigen was cloned, sequenced and expressed in e. coli. alignment with ovine pulmonary carcinoma (opc) virus showed 93% nucleotide and 96% amino acid homology. no amplification occurred when dna from ovine fetal cell line was used as template. the recombinant protei ... | 1996 | 9008337 |
| cleavage of vimentin by different retroviral proteases. | proteases (prs) of retroviruses cleave viral polyproteins into their mature structural proteins and replication enzymes. besides this essential role in the replication cycle of retroviruses, prs also cleave a variety of host cell proteins. we have analyzed the in vitro cleavage of mouse vimentin by proteases of human immunodeficiency virus type 1 (hiv-1) and type 2 (hiv-2), bovine leukemia virus (blv), mason-pfizer monkey virus (m-pmv), myeloblastosis-associated virus (mav), and two active-site ... | 2000 | 10845700 |
| solution structure and backbone dynamics of mason-pfizer monkey virus (mpmv) nucleocapsid protein. | retroviral nucleocapsid proteins (ncps) are cchc-type zinc finger proteins that mediate virion rna binding activities associated with retrovirus assembly and genomic rna encapsidation. mason-pfizer monkey virus (mpmv), a type d retrovirus, encodes a 96-amino acid nucleocapsid protein, which contains two cys-x2-cys-x4-his-x4-cys (cchc) zinc fingers connected by an unusually long 15-amino acid linker. homonuclear, two-dimensional sensitivity-enhanced 15n-1h, three-dimensional 15n-1h, and triple re ... | 1998 | 9827993 |
| requirements for efficient production and transduction of human immunodeficiency virus type 1-based vectors. | a number of human immunodeficiency type 1 (hiv-1)-based vectors have recently been shown to transduce nondividing cells in vivo as well as in vitro. however, if these vectors are to be considered for eventual clinical use, a major consideration is to reduce the probability of unintended generation of replication-competent virus. this can be achieved by eliminating viral genetic elements involved in the generation of replication-competent virus without impairing vector production. we have designe ... | 1999 | 9971760 |
| type d retroviruses from human cells do not contain a minor glycoprotein shared by old world monkey type d viruses. | the protein patterns of type d retroviruses isolated either from permanent human cells (hela virus, hela v, and hep-2 virus, hep-2v) or from spectacled langur (langur virus, lv), an old world monkey, were investigated using sodium dodecyl sulfate polyacrylamide gel electrophoresis. labeling with 14c-amino acids and 3h-glucosamine revealed for each of these isolates five polypeptides with molecular weights of 10,000, 12,000, 15,000, 25,000 and about 68,000 and identified the 68,000 d-protein as a ... | 1981 | 7332488 |
| analysis of mason-pfizer monkey virus gag domains required for capsid assembly in bacteria: role of the n-terminal proline residue of ca in directing particle shape. | mason-pfizer monkey virus (m-pmv) preassembles immature capsids in the cytoplasm prior to transporting them to the plasma membrane. expression of the m-pmv gag precursor in bacteria results in the assembly of capsids indistinguishable from those assembled in mammalian cells. we have used this system to investigate the structural requirements for the assembly of gag precursors into procapsids. a series of c- and n-terminal deletion mutants progressively lacking each of the mature gag domains (mat ... | 2000 | 10954545 |
| identification of a cytoplasmic targeting/retention signal in a retroviral gag polyprotein. | retroviral capsid assembly can occur by either of two distinct morphogenic processes: in type c viruses, the capsid assembles and buds at the plasma membrane, while in type b and d viruses, the capsid assembles within the cytoplasm and is then transported to the plasma membrane for budding. we have previously reported that a single-amino-acid substitution of a tryptophan for an arginine in the matrix protein (ma) of mason-pfizer monkey virus (mpmv) converts its capsid assembly from that of a typ ... | 1999 | 10364290 |
| serum antibodies reactive with non-human primate retroviruses identified in acute onset schizophrenia. | schizophrenia is a pervasive neuropsychiatric disease of uncertain etiology. previous studies have postulated that retroviruses may contribute to the etiology of some cases of schizophrenia. we examined the possible relationship between retroviral infection and schizophrenia by measuring antibodies to a number of different primate retroviruses in the sera of individuals undergoing their first hospitalization for this disease. sera from patients with first onset schizophrenia and matched healthy ... | 2000 | 11175321 |
| detection of squirrel monkey retroviral sequences in interferon samples. | interferons have been used therapeutically in viral infections, and as immunomodulants in the treatment of different types of cancers. interferons have been prepared from human lymphoid cell-lines, such as namalwa, that contain integrated copies of squirrel monkey retrovirus proviral dna. squirrel monkey retrovirus is related to simian type d retroviruses, such as mason-pfizer monkey virus. thus it is important to determine if these retroviral sequences are present in interferon preparations pur ... | 1998 | 9551676 |
| cofactor requirements for nuclear export of rev response element (rre)- and constitutive transport element (cte)-containing retroviral rnas. an unexpected role for actin. | nuclear export of proteins containing leucine-rich nuclear export signals (ness) is mediated by the export receptor crm1/exportin1. however, additional protein factors interacting with leucine-rich ness have been described. here, we investigate human immunodeficiency virus type 1 (hiv-1) rev-mediated nuclear export and mason-pfizer monkey virus (mpmv) constitutive transport element (cte)-mediated nuclear export in microinjected xenopus laevis oocytes. we show that eukaryotic initiation factor 5a ... | 2001 | 11238447 |
| a proline-rich motif (pppy) in the gag polyprotein of mason-pfizer monkey virus plays a maturation-independent role in virion release. | virus assembly represents one of the last steps in the retrovirus life cycle. during this process, gag polyproteins assemble at specific sites within the cell to form viral capsids and induce membrane extrusion (viral budding) either as assembly progresses (type c virus) or following formation of a complete capsid (type b and type d viruses). finally, the membrane must undergo a fusion event to pinch off the particle in order to release a complete enveloped virion. structural elements within the ... | 1998 | 9557699 |
| defective lentiviral vectors are efficiently trafficked by hiv-1 and inhibit its replication. | gene therapy against hiv infection should involve vector-mediated delivery of anti-hiv therapeutic genes into t-lymphocytes and macrophages or, alternatively, hematopoietic progenitors. transduction of mature cells with defective vectors would have limited success because the vector would disappear with cell turnover. however, if a vector could be trafficked by wild-type hiv, initial transduction of a majority of the population would not be required, as the vector would be able to spread. we des ... | 2001 | 11407907 |
| analysis of autoprocessing of mason-pfizer monkey virus proteinase in vitro. three active forms of proteinase. | | 1998 | 9561206 |
| three active forms of aspartic proteinase from mason-pfizer monkey virus. | mason-pfizer monkey virus (m-pmv) proteinase, released by the autocatalytic cleavage of gag-pro and gag-pro-pol polypeptide precursors, catalyzes the processing of viral precursors to yield the structural proteins and enzymes of the virion. in retroviruses, usually only one proteolytically active form of proteinase exists. here, we describe an unusual feature of m-pmv, the existence of three active forms of a retroviral proteinase with molecular masses of 17, 13, and 12 kda as determined by mass ... | 1998 | 9636364 |
| leptomycin b inhibits equine infectious anemia virus rev and feline immunodeficiency virus rev function but not the function of the hepatitis b virus posttranscriptional regulatory element. | human immunodeficiency virus type 1 rev export depends upon the presence of the nuclear export signal (nes), a leucine-rich stretch of hydrophobic amino acids. recently, the nuclear nes-binding receptor has been identified as crm1 or exportin 1. rev export has been shown to be crm1 dependent. the function of the atypical nes-containing rev-like proteins of equine infectious anemia virus (eiav) and feline immunodeficiency virus (fiv) is inhibited by leptomycin b, a drug that specifically blocks n ... | 1998 | 9696859 |
| analysis of the rna binding specificity of the human tap protein, a constitutive transport element-specific nuclear rna export factor. | the human tap protein has been proposed to mediate mason pfizer monkey virus constitutive transport element (cte)-dependent nuclear rna export and may also play a role in global mrna export. here, we have used in vivo assays, in both yeast and human cells, together with in vitro assays, to further characterize the rna binding properties of tap, which has been proposed to contain a novel leucine-rich rna binding motif. using the yeast three hybrid assay, we selected rna molecules that retain tap ... | 1999 | 10489353 |
| a lentivirus packaging system based on alternative rna transport mechanisms to express helper and gene transfer vector rnas and its use to study the requirement of accessory proteins for particle formation and gene delivery. | a lentivirus-based packaging system was designed to reduce the chance of recombination between helper and gene transfer vector sequences by using the constitutive transport element (cte) derived from mason-pfizer monkey virus for expression of the viral proteins and the rev-rev response element (rre) combination for expression of the gene transfer vector. using this approach, we evaluated a series of human immunodeficiency virus type 1 packaging constructs that express one or more accessory prot ... | 1999 | 10516068 |
| cellular motor protein kif-4 associates with retroviral gag. | previously we demonstrated that murine retroviral gag proteins associate with a cellular motor protein, kif-4. using the yeast two-hybrid assay, we also found an association of kif-4 with gag proteins of mason-pfizer monkey virus (mpmv), simian immunodeficiency virus (siv), and human immunodeficiency virus type 1 (hiv-1). studies performed with mammalian cell systems confirmed that the hiv-1 gag protein associates with kif-4. soluble cytoplasmic proteins from cells infected with recombinant vacc ... | 1999 | 10559369 |
| inhibition of human immunodeficiency virus rev and human t-cell leukemia virus rex function, but not mason-pfizer monkey virus constitutive transport element activity, by a mutant human nucleoporin targeted to crm1. | the hypothesis that the cellular protein crm1 mediates human immunodeficiency virus type 1 (hiv-1) rev-dependent nuclear export posits that crm1 can directly interact both with the rev nuclear export signal (nes) and with cellular nucleoporins. here, we demonstrate that crm1 is indeed able to interact with active but not defective forms of the hiv-1 rev nes and of ness found in other retroviral nuclear export factors. in addition, we demonstrate that crm1 can bind the rev nes when rev is assembl ... | 1998 | 9765402 |
| structural and functional analysis of the avian leukemia virus constitutive transport element. | the observation that cells restrict the nuclear export of incompletely spliced transcripts via the canonical nuclear mrna export pathway implies that all retroviruses should have evolved a way to direct the unspliced form of their genomic rna into an alternate export pathway. while the crm1-dependent pathway used by complex retroviruses to export incompletely spliced viral transcripts is now fairly well understood, less is known about how simple retroviruses accomplish this task. however, the ma ... | 1999 | 10606274 |
| a cell-line-specific defect in the intracellular transport and release of assembled retroviral capsids. | retrovirus assembly involves a complex series of events in which a large number of proteins must be targeted to a point on the plasma membrane where immature viruses bud from the cell. gag polyproteins of most retroviruses assemble an immature capsid on the cytoplasmic side of the plasma membrane during the budding process (c-type assembly), but a few assemble immature capsids deep in the cytoplasm and are then transported to the plasma membrane (b- or d-type assembly), where they are enveloped. ... | 2000 | 10623740 |
| multiple copies of the mason-pfizer monkey virus constitutive rna transport element lead to enhanced hiv-1 gag expression in a context-dependent manner. | retroviral gene expression requires nuclear export and translation of incompletely spliced rna. in the case of human immunodeficiency virus (hiv), this is facilitated by the viral rev protein binding to its cognate rna response element (rre), while other retroviruses contain constitutive transport elements (cte) binding to cellular factors. these cte can substitute for the hiv-1 rev/rre system, albeit with reduced efficiency. here, we show that multimeric copies of the cte restore hiv-1 protein ... | 2000 | 10648781 |
| the nmr structure of the nucleocapsid protein from the mouse mammary tumor virus reveals unusual folding of the c-terminal zinc knuckle. | the nucleocapsid protein (nc) from the mouse mammary tumor virus (mmtv) has been overexpressed in escherichia coli and purified to homogeneity for structural studies by nuclear magnetic resonance (nmr) spectroscopy. the protein contains two copies of a conserved zinc-coordinating "cchc array" or "zinc knuckle" motif common to the nucleocapsid proteins of nearly all known retroviruses. the residues comprising and adjacent to the zinc knuckles were assigned by standard two-dimensional (1)h and thr ... | 2000 | 10677209 |
| improved safety and titre of murine leukaemia virus (mlv)-based retroviral vectors. | many retroviral vectors based on murine leukaemia virus (mlv) contain the first 420 nucleotides of the gag gene, as this was reported to increase vector titre by increasing the efficiency of rna packaging. in this study, deletion of this gag sequence from its original location did not decrease the titre of two retroviral vectors, pbabe puro and mfg-s-. the two vectors could be improved by replacing the gag sequence with a cte from mason-pfizer monkey virus (mpmv). this substitution improved vect ... | 2000 | 10694810 |
| role of matrix protein in the type d retrovirus replication cycle: importance of the arginine residue at position 55. | we previously reported that a mutant of mason-pfizer monkey virus (m-pmv), which has an amino acid substitution in the matrix (ma) protein at position 55, ma-r55w, showed altered viral morphogenesis, reduced glycoprotein incorporation, and loss of infectivity. in this report, we show that two additional amino acid substitutions at this site in ma, r55f and r55y, also result in similar altered morphogenesis, env incorporation, and infectivity, demonstrating that these changes are not specific for ... | 2000 | 10704360 |
| type d retrovirus markers in healthy africans from guinea. | sixteen matching sera and dna samples from healthy african blood donors living in rural areas of guinea were analysed for the presence of type d retrovirus markers. screening for the antibodies against structural proteins of mason-pfizer monkey virus (m-pmv) was carried out by western blot with a purified m-pmv as an antigen. eight out of 16 sera samples were found to contain antibodies against at least two gag gene-coded proteins, and three of these were weakly positive against env gene-coded p ... | 1996 | 8958587 |
| mason-pfizer monkey virus (mpmv) constitutive transport element (cte) functions in a position-dependent manner. | the mason-pfizer monkey virus (mpmv) constitutive transport element (cte) is a cis-acting rna element located in the 3' untranslated region (utr) of the viral genome. the hiv-1 and siv rev/rre regulatory system can be replaced with mpmv cte (bray et al., 1994; zolotukhin et al., 1994; rizvi et al., 1996a); similarly, cte function can also be replaced by the hiv or siv rev/rre regulatory system (rizvi et al., 1996b; ernst et al., 1997). in addition, we have shown that in the context of the siv ge ... | 1997 | 9299624 |
| the constitutive transport element (cte) of mason-pfizer monkey virus (mpmv) accesses a cellular mrna export pathway. | the constitutive transport elements (ctes) of type d retroviruses are cis-acting elements that promote nuclear export of incompletely spliced mrnas. unlike the rev response element (rre) of human immunodeficiency virus type 1 (hiv-1), ctes depend entirely on factors encoded by the host cell genome. we show that an rna comprised almost entirely of the cte of mason-pfizer monkey virus (cte rna) is exported efficiently from xenopus oocyte nuclei. the cte rna and an rna containing the rre of hiv-1 ( ... | 1997 | 9405378 |
| type d retrovirus capsid assembly and release are active events requiring atp. | mason-pfizer monkey virus (m-pmv), the prototype type d retrovirus, differs from most other retroviruses by assembling its gag polyproteins into procapsids in the cytoplasm of infected cells. once assembled, the procapsids migrate to the plasma membrane, where they acquire their envelope during budding. because the processes of m-pmv protein transport, procapsid assembly, and budding are temporally and spatially unlinked, we have been able to determine whether cellular proteins play an active ro ... | 1998 | 9525635 |
| novel tat-encoding bicistronic human immunodeficiency virus type 1-based gene transfer vectors for high-level transgene expression. | we describe bicistronic single-exon tat (72-amino-acid tat [tat72])- and full-length tat (tat86)-encoding gene transfer vectors based on human immunodeficiency virus type 1 (hiv-1). we created versions of these vectors that were rendered rev independent by using the constitutive transport element (cte) from mason-pfizer monkey virus (mpmv). tat72-encoding vectors performed better than tat86-expressing vectors in gene transfer experiments. cte-containing vectors, produced in a rev-independent pac ... | 2000 | 10864682 |
| identification of two intracellular mechanisms leading to reduced expression of oncoretrovirus envelope glycoproteins at the cell surface. | all retrovirus glycoproteins have a cytoplasmic domain that plays several roles in virus replication. we have determined whether and how the cytoplasmic domains of oncoretrovirus glycoproteins modulate their intracellular trafficking, by using chimeric proteins that combined the alpha-chain of the interleukin-2 receptor with the glycoprotein cytoplasmic domains of five oncoretroviruses: human t-cell leukemia virus type 1 (htlv-1), rous sarcoma virus (rsv), bovine leukemia virus (blv), murine leu ... | 2000 | 11090173 |
| an intact tar element and cytoplasmic localization are necessary for efficient packaging of human immunodeficiency virus type 1 genomic rna. | although most reports defining the human immunodeficiency virus type 1 (hiv-1) genomic rna packaging signal have focused on the region downstream of the major 5' splice site, others have suggested that sequences upstream of the splice site may also play an important role. in this study we have directly examined the role played by the hiv-1 tar region in rna packaging. for these experiments we used a proviral expression system that is largely independent of tat for transcriptional activation. thi ... | 1999 | 10196309 |
| type d retrovirus gag polyprotein interacts with the cytosolic chaperonin tric. | the carboxy terminus-encoding portion of the gag gene of mason-pfizer monkey virus (m-pmv), the prototype immunosuppressive primate type d retrovirus, encodes a 36-amino-acid, proline-rich protein domain that, in the mature virion, becomes the p4 capsid protein. the p4 domain has no known role in m-pmv replication. we found that two mutants with premature termination codons that remove half or all of the p4 domain produced lower levels of stable gag protein and of self-assembled capsids. interes ... | 2001 | 11222675 |
| primate and feline lentivirus vector rna packaging and propagation by heterologous lentivirus virions. | development of safe and effective gene transfer systems is critical to the success of gene therapy protocols for human diseases. currently, several primate lentivirus-based gene transfer systems, such as those based on human and simian immunodeficiency viruses (hiv/siv), are being tested; however, their use in humans raises safety concerns, such as the generation of replication-competent viruses through recombination with related endogenous retroviruses or retrovirus-like elements. due to the gr ... | 2001 | 11333894 |
| the envelope of mason-pfizer monkey virus has immunosuppressive properties. | we have demonstrated previously that the envelope protein of a murine retrovirus, moloney murine leukaemia virus, has immunosuppressive properties in vivo. this property was manifested by the ability of the protein, when expressed by tumour cells normally rejected by engrafted mice, to allow the env-expressing cells to escape immune rejection and to proliferate. here, it is shown that this property is not restricted to the envelope of a murine retrovirus, but is also shared by the envelope encod ... | 2001 | 11413370 |
| identification of a conserved residue of foamy virus gag required for intracellular capsid assembly. | in contrast to all retroviruses but similar to the hepatitis b virus, foamy viruses (fv) require expression of the envelope protein for budding of intracellular capsids from the cell, suggesting a specific interaction between the gag and env proteins. capsid assembly occurs in the cytoplasm of infected cells in a manner similar to that for the b- and d-type viruses; however, in contrast to these retroviruses, fv gag lacks an n-terminal myristylation signal and capsids are not targeted to the pla ... | 2001 | 11435565 |
| type d retrovirus specific sequences in lymphocytes of the children with burkitt-type lymphoma and their parents. | type d retroviruses cause immunodeficiency in monkey. earlier we have revealed genetical and serological markers of type d retroviruses in children with burkitt-type lymphoma. using pcr/southern blotting assay we have found sequences related to mpmv in pbmc's dna from children with burkitt-type lymphoma and from their parents. moreover, the data on sequencing of virus specific sequences from one ill child and from his mother have been presented. | 2001 | 11470152 |
| a spontaneously occuring mammary gland ductal carcinoma in situ in a rhesus macaque (macaca mulatta) and a review of spontaneous mammary gland tumors in rhesus monkeys. | a spontaneous mammary gland ductal carcinoma in situ was diagnosed in a 6-8-year-old female rhesus macaque (macaca mulatta). to our knowledge, this is only the tenth case of spontaneous mammary gland tumors to be reported in rhesus monkeys. despite the paucity of case reports, several theories exist to explain the occurrence of mammary tumors. the mason pfizer monkey virus, a type d retrovirus similar to the virus that causes simian acquired immunodeficiency syndrome, has been implicated as a po ... | 2001 | 11491405 |
| backbone resonance assignment of protease from mason-pfizer monkey virus. | | 2001 | 11519753 |
| analysis of mason-pfizer monkey virus gag particles by scanning transmission electron microscopy. | mason-pfizer monkey virus immature capsids selected from the cytoplasm of baculovirus-infected cells were imaged by scanning transmission electron microscopy. the masses of individual selected gag particles were measured, and the average mass corresponded to 1,900 to 2,100 gag polyproteins per particle. a large variation in gag particle mass was observed within each population measured. | 2001 | 11533218 |
| sequences in the 5' leader of mason-pfizer monkey virus which affect viral particle production and genomic rna packaging: development of mpmv packaging cell lines. | we used a series of deletion mutations in the 5' untranslated region of the prototype d type retrovirus, mason-pfizer monkey virus (mpmv), to analyse rna encapsidation. a region was identified upstream of the major splice donor which reduced particle production but had a proportionally greater effect on rna packaging. a small deletion downstream of the splice donor had little effect on rna production and caused no significant packaging defect. a large deletion encompassing the end of the primer ... | 2001 | 11543660 |
| the full-length envelope of an herv-h human endogenous retrovirus has immunosuppressive properties. | we have demonstrated previously that the envelope proteins of a murine retrovirus (moloney murine leukaemia virus) and a simian retrovirus (mason-pfizer monkey virus) have immunosuppressive properties in vivo. this property was manifested by the ability of the proteins, when expressed by tumour cells normally rejected by engrafted mice, to allow the envelope-expressing cells to escape immune rejection and to proliferate. here, it is shown that this property is not restricted to the envelope of i ... | 2001 | 11562544 |
| comparison of classical and affinity purification techniques of mason-pfizer monkey virus capsid protein: the alteration of the product by an affinity tag. | the efficiencies of different procedures for purification of the capsid protein (ca) of mason-pfizer monkey virus are compared. plasmids encoding both wild-type ca and two c-terminally modified sequences of ca suitable for affinity chromatography purification were prepared. ca was expressed in escherichia coli (i) as a wild-type protein, (ii) c-terminally extended with a six-histidine tag (ca 6his), and (iii) as a protein containing a c-terminal fusion to a viral protease cleavage site followed ... | 2001 | 11570848 |
| rna export mediated by tap involves nxt1-dependent interactions with the nuclear pore complex. | nuclear export of ribonucleoprotein complexes requires cis-acting signals and recognition by receptors that mediate translocation through the nuclear pore complex. translocation is likely to involve a series of physical interactions between the ribonucleoprotein complex and nucleoporins within the nuclear pore complex. here, we have characterized the function of nxt1 in the context of the tap-dependent rna export pathway. tap has been implicated in the nuclear export of rna transcripts derived f ... | 2001 | 11579093 |
| a new rna element located in the coding region of a murine endogenous retrovirus can functionally replace the rev/rev-responsive element system in human immunodeficiency virus type 1 gag expression. | nuclear export of incompletely spliced rnas is a prerequisite for retroviral replication. complex retroviruses like human immunodeficiency virus (hiv) encode a viral transport factor (rev), which binds to its target sequence on the rna genome and directs it into the crm-1-mediated export pathway. other retroviruses, like mason-pfizer monkey virus, contain cis-acting constitutive rna transport elements (cte) which achieve nuclear export of intron-containing rna via cellular transport factors. her ... | 2001 | 11602709 |
| activation of the mason-pfizer monkey virus protease within immature capsids in vitro. | for all retroviruses, the completion of the viral budding process correlates with the activation of the viral protease by an unknown mechanism, and, as the structural (gag) polyproteins are cleaved by the viral protease, maturation of the immature virus-like particle into an infectious virion. unlike most retroviruses, the mason-pfizer monkey virus gag polyproteins assemble into immature capsids within the cytoplasm of the cell before the viral budding event. the results reported here describe a ... | 2001 | 11724937 |
| overexpression of the n-terminal domain of tsg101 inhibits hiv-1 budding by blocking late domain function. | efficient budding of hiv-1 from the plasma membrane of infected cells requires the function of a 6-kda protein known as p6. a highly conserved pro-thr-ala-pro (ptap) motif (the "late" or "l" domain), is critical for the virus-budding activity of p6. recently, it was demonstrated that the product of tumor susceptibility gene 101 (tsg101), which contains at its n terminus a domain highly related to ubiquitin-conjugating (e2) enzymes, binds hiv-1 gag in a p6-dependent fashion. we examined the impac ... | 2002 | 11805336 |
| the murine endogenous retrovirus mia14 encodes an active aspartic proteinase that is functionally similar to proteinases from d-type retroviruses. | murine intracisternal a-type particles (iaps) are endogenous retroviruses showing sequence homologies to b/d- and avian c-type retroviruses and a gene expression strategy similar to that of d-type retroviruses. these viruses form immature particles in the endoplasmic reticulum and do not release extracellular virions, but are competent for retrotransposition within the virus-producing cell. it had been assumed that lack of polyprotein processing and maturation is due to a defect in the viral pro ... | 2002 | 11831858 |
| molecular organization of mason-pfizer monkey virus capsids assembled from gag polyprotein in escherichia coli. | we describe the results of a study by electron microscopy and image processing of gag protein shells-immature capsids--of mason-pfizer monkey virus assembled in escherichia coli from two truncated forms of the gag precursor: deltap4gag, in which the c-terminal p4gag was deleted, and pro(-)ca.nc, in which the n-terminal peptides and proline 1 of the ca domain were deleted. negative staining of capsids revealed small patches of holes forming a trigonal or hexagonal pattern most clearly visible on ... | 2002 | 11932398 |
| spectroscopic characterization of co(ii)-, ni(ii)-, and cd(ii)-substituted wild-type and non-native retroviral-type zinc finger peptides. | the nucleocapsid protein (ncp) from mason-pfizer monkey virus (mpmv) contains two evolutionary invariant cys-x2-cys-x4-his-x4-cys retroviral-type zinc finger structures, where the cys and his residues provide ligands to a tetrahedrally coordinated zn(ii) ion. the n-terminal zinc finger (f1) of ncp from mpmv contains an immediately contiguous cys in the -1 position relative to the start of this conserved motif: cys-cys-x2-cys-x4-his-x4-cys. metal complexes of 18-amino acid peptides which model th ... | 2000 | 10766441 |
| analysis of cellular factors that mediate nuclear export of rnas bearing the mason-pfizer monkey virus constitutive transport element. | there is now convincing evidence that the human tap protein plays a critical role in mediating the nuclear export of mrnas that contain the mason-pfizer monkey virus constitutive transport element (cte) and significant evidence that tap also participates in global poly(a)(+) rna export. previously, we had mapped carboxy-terminal sequences in tap that serve as an essential nucleocytoplasmic shuttling domain, while others had defined an overlapping tap sequence that can bind to the fg repeat domai ... | 2000 | 10846066 |
| sam68 enhances the cytoplasmic utilization of intron-containing rna and is functionally regulated by the nuclear kinase sik/brk. | cells normally restrict the nuclear export and expression of intron-containing mrna. in many cell lines, this restriction can be overcome by inclusion of cis-acting elements, such as the mason-pfizer monkey virus constitutive transport element (cte), in the rna. in contrast, we observed that cte-mediated expression from human immunodeficiency virus gag-pol reporters was very inefficient in 293 and 293t cells. however, addition of sam68 led to a dramatic increase in the amount of gag-pol proteins ... | 2003 | 12482964 |
| [integration of the type d mason-pfizer monkey virus into the human chromosome]. | | 2002 | 12500538 |
| rabbit endogenous retrovirus-h encodes a functional protease. | recent studies have revealed that 'human retrovirus-5' sequences found in human samples belong to a rabbit endogenous retrovirus family named rerv-h. a part of the gag-pro region of the rerv-h genome was amplified by pcr from dna in human samples and several forms of rerv-h protease were expressed in bacteria. the rerv-h protease was able to cleave itself from a precursor protein and was also able to cleave the rerv-h gag polyprotein precursor in vitro whereas a form of the protease with a mutat ... | 2003 | 12533718 |
| retroviruses have differing requirements for proteasome function in the budding process. | proteasome inhibitors reduce the budding of human immunodeficiency virus types 1 (hiv-1) and 2, simian immunodeficiency virus, and rous sarcoma virus. to investigate this effect further, we examined the budding of other retroviruses from proteasome inhibitor-treated cells. the viruses tested differed in their gag organization, late (l) domain usage, or assembly site from those previously examined. we found that proteasome inhibition decreased the budding of murine leukemia virus (plasma membrane ... | 2003 | 12610113 |
| a tyrosine motif in the cytoplasmic domain of mason-pfizer monkey virus is essential for the incorporation of glycoprotein into virions. | mason-pfizer monkey virus (m-pmv) encodes a transmembrane (tm) glycoprotein with a 38-amino-acid-long cytoplasmic domain. after the release of the immature virus, a viral protease-mediated cleavage occurs within the cytoplasmic domain, resulting in the loss of 17 amino acids from the carboxy terminus. this maturational cleavage occurs between a histidine at position 21 and a tyrosine at position 22 in the cytoplasmic domain of the tm protein. we have demonstrated previously that a truncated tm g ... | 2003 | 12692221 |
| sequences within both the 5' untranslated region and the gag gene are important for efficient encapsidation of mason-pfizer monkey virus rna. | it has previously been shown that the 5' untranslated leader region (utr), including about 495 bp of the gag gene, is sufficient for the efficient encapsidation and propagation of mason-pfizer monkey virus (mpmv) based retroviral vectors. in addition, a deletion upstream of the major splice donor, sd, has been shown to adversely affect mpmv rna packaging. however, the precise sequence requirement for the encapsidation of mpmv genomic rna within the 5' utr and gag remains largely unknown. in this ... | 2003 | 12726736 |
| specific in vitro cleavage of mason-pfizer monkey virus capsid protein: evidence for a potential role of retroviral protease in early stages of infection. | processing of gag polyproteins by viral protease (pr) leads to reorganization of immature retroviral particles and formation of a ribonucleoprotein core. in some retroviruses, such as hiv and rsv, cleavage of a spacer peptide separating capsid and nucleocapsid proteins is essential for the core formation. we show here that no similar spacer peptide is present in the capsid-nucleocapsid (ca-nc) region of mason-pfizer monkey virus (m-pmv) and that the ca protein is cleaved in vitro by the pr withi ... | 2003 | 12781718 |
| variable sensitivity to substitutions in the n-terminal heptad repeat of mason-pfizer monkey virus transmembrane protein. | the transmembrane protein of mason-pfizer monkey virus contains two heptad repeats that are predicted to form amphipathic alpha-helices that mediate the conformational change necessary for membrane fusion. to analyze the relative sensitivity of the predicted hydrophobic face of the n-terminal heptad repeat to the insertion of uncharged, polar, and charged substitutions, mutations that introduced alanine, serine, or glutamic acid into positions 436, 443, 450, and 457 of the envelope protein were ... | 2003 | 12829817 |
| dutpase and nucleocapsid polypeptides of the mason-pfizer monkey virus form a fusion protein in the virion with homotrimeric organization and low catalytic efficiency. | betaretroviruses encode dutpase, an essential factor in dna metabolism and repair, in the pro open reading frame located between gag and pol. ribosomal frame-shifts during expression of retroviral proteins provide a unique possibility for covalent joining of nucleocapsid (nc) and dutpase within gag-pro polyproteins. by developing an antibody against the prototype betaretrovirus mason-pfizer monkey virus dutpase, we demonstrate that i) the nc-dutpase fusion protein exists both within the virions ... | 2003 | 12869552 |
| a hepadnavirus regulatory element enhances expression of a type 2 bovine viral diarrhea virus e2 protein from a bovine herpesvirus 1 vector. | recently, the possibility of using virus vectors to immunize cattle against selected bovine viral diarrhea virus (bvdv) genes has gained widespread interest. however, when we attempted to express the e2 protein from type 2 (890 strain) bvdv in a bovine herpesvirus 1 (bhv1) vector, we observed that expression was poor. this often happens when genes from a cytoplasmic virus are expressed in the cell nucleus. to counter this effect, we attempted to enhance expression by a strategy employed by virus ... | 2003 | 12885896 |
| luminometric method for screening retroviral protease inhibitors. | we have developed a sensitive luminometric assay for determining the activity of retroviral proteases that uses proteolytic cleavage of polypeptide substrate immobilized on ni-nta hissorb strips microplates. the protease substrate derived from the gag precursor protein of mason-pfizer monkey virus (m-pmv) was conjugated with horseradish peroxidase (hrp), which catalyzes oxidation of luminol in the assay. the cleavage of the substrate was monitored as a decrease in luminescent signal caused by th ... | 2005 | 16125122 |
| the mason-pfizer monkey virus pppy and psap motifs both contribute to virus release. | late (l) domains are required for the efficient release of several groups of enveloped viruses. three amino acid motifs have been shown to provide l-domain function, namely, ppxy, pt/sap, or ypdl. the retrovirus mason-pfizer monkey virus (mpmv) carries closely spaced pppy and psap motifs. mutation of the pppy motif results in a complete loss of virus release. here, we show that the psap motif acts as an additional l domain and promotes the efficient release of mpmv but requires an intact pppy mo ... | 2003 | 12915562 |
| nedd4 regulates egress of ebola virus-like particles from host cells. | ebola virus budding is mediated by two proline-rich motifs, ppxy and ptap, within the viral matrix protein vp40. we have previously shown that a nedd4-like protein bul1, but not nedd4, positively regulates budding of type d retrovirus mason-pfizer monkey virus (j. yasuda, e. hunter, m. nakao, and h. shida, embo rep. 3:636-640, 2002). here, we report that the cellular e3 ubiquitin ligase nedd4 regulates budding of vp40-induced virus-like particles (vlps) through interaction with the ppxy motif. m ... | 2003 | 12941909 |
| the m-pmv cytoplasmic targeting-retention signal directs nascent gag polypeptides to a pericentriolar region of the cell. | intracytoplasmic protein targeting in mammalian cells is critical for organelle function as well as virus assembly, but the signals that mediate it are poorly defined. we show here that mason-pfizer monkey virus specifically targets gag precursor proteins to the pericentriolar region of the cytoplasm in a microtubule dependent process through interactions between a short peptide signal, known as the cytoplasmic targeting-retention signal, and the dynein/dynactin motor complex. the gag molecules ... | 2003 | 12956869 |
| m-pmv capsid transport is mediated by env/gag interactions at the pericentriolar recycling endosome. | cytoplasmic transport of gag molecules to the site of budding is an important but poorly understand process in retroviral assembly. our previous studies of mason-pfizer monkey virus showed that, for this retrovirus, gag is assembled into capsids at a pericentriolar region and that env is necessary for efficient transport out of the site. an env requirement for cytoplasmic transport implicates vesicular trafficking in this process even though the capsids remain cytoplasmic and do not bud into int ... | 2003 | 12956870 |
| rescue of internal scaffold-deleted mason-pfizer monkey virus particle production by plasma membrane targeting. | the mason-pfizer monkey virus (m-pmv) gag protein follows a morphogenesis pathway in which immature capsids are preassembled within the cytoplasm before interaction with and budding through the plasma membrane. intracytoplasmic assembly is facilitated by sequences within the p12 domain of gag that we have termed the internal scaffold domain (isd). if m-pmv utilizes an isd then what provides the equivalent function for most other retroviruses that assemble at the plasma membrane? to investigate t ... | 2006 | 16297423 |
| mason-pfizer monkey virus gag proteins interact with the human sumo conjugating enzyme, hubc9. | retroviral gag proteins function during early and late stages of the viral life cycle. to gain additional insight into the cellular requirements for viral replication, a two-hybrid screen was used to identify cellular proteins that interact with the mason-pfizer monkey virus gag protein. one of the cellular proteins found was identified as hubc9, a nuclear pore-associated e2 sumo conjugating enzyme. in vitro protein interaction assays verified the association and mapped the interaction domain to ... | 2003 | 14517060 |
| three-dimensional structure of a monomeric form of a retroviral protease. | the assembly of mason-pfizer monkey virus gag polyproteins into immature capsids and their cleavage by the encoded protease are temporally and spatially separated processes, making the virus a particularly useful model for investigation of protease activation. here we present a high resolution nmr structure of a fully folded monomer of a 12 kda m-pmv protease (wt 12 pr) and of a cys7ala/asp26asn/cys106ala mutant (12 pr(d26n/c7a/c106a)). the overall structures of both wt 12 pr and 12 pr(d26n/c7a/ ... | 2003 | 14568536 |
| [construction of recombinant lentivirus vaccine with single round replication]. | to develop a safe and effective lentivirus vaccine model and provide insights into the development of other lentivirus vaccines. | 2006 | 16792898 |
| the endogenous langur type d retrovirus po-1-lu and its exogenous counterparts in macaque and langur monkeys. | po-1-lu, the endogenous type d retrovirus of langurs (trachypithecus obscurus) has previously been considered a progenitor to the prototype type d retrovirus, mason pfizer monkey virus (m-pmv/srv-3), that became established in macaque monkeys (macaca spp.) following a zoonosis. this study reevaluates this hypothesis to include other exogenous srvs. new sequence information from the gp70(su)-encoding region of po-1-lu shows striking similarity to the newly identified exogenous langur retrovirus, ... | 2003 | 14585330 |
| mutational analysis of the predicted secondary rna structure of the mason-pfizer monkey virus packaging signal. | the 5' end of the mason-pfizer monkey virus (mpmv) genomic rna has been predicted to fold into a complex stem/loop structure that is thought to play a role in specific rna encapsidation. in this study, we used a set of mutations that either abrogated or recreated the first four stem loops predicted within the 5' untranslated region (5' utr) for effects on rna packaging. test of these mutations in our biological assay revealed that only stem loop 1 (sl1) was important for the packaging potential ... | 2004 | 14687944 |
| functional involvement of a novel nedd4-like ubiquitin ligase on retrovirus budding. | in this study, we have identified a novel nedd4-like ubiquitin ligase, bul1, as the host factor involved in budding of type d retrovirus mason-pfizer monkey virus (m-pmv). overexpression of bul1 enhanced virus particle release, while a bul1 mutant in which a w to g substitution was introduced into a ww domain, w791g, lost the ability to bind to the viral gag protein and abolished its ability to mediate virus budding. in addition, a fragment of bul1 containing only the ww domains inhibited virus ... | 2002 | 12101095 |
| the betaretrovirus mason-pfizer monkey virus selectively excludes simian apobec3g from virion particles. | the apobec3 protein family can constitute a potent barrier to the successful infection of mammalian species by retroviruses. therefore, any retrovirus that has evolved the ability to replicate in a given animal must have developed mechanisms that allow it to avoid or inhibit the apobec3 proteins expressed in that animal. here, we demonstrate that mason-pfizer monkey virus (mpmv) is resistant to inhibition by the apobec3g protein expressed in its normal host, the rhesus macaque, but highly suscep ... | 2006 | 17035335 |
| ru5 of mason-pfizer monkey virus 5' long terminal repeat enhances cytoplasmic expression of human immunodeficiency virus type 1 gag-pol and nonviral reporter rna. | retroviruses utilize an unspliced version of their primary transcription product as an rna template for synthesis of viral gag and pol structural and enzymatic proteins. cytoplasmic expression of the gag-pol rna is achieved despite the lack of intron removal and the presence of a long and highly structured 5' untranslated region that inhibits efficient ribosome scanning. in this study, we have identified for the first time that the 5' long terminal repeat (ltr) of mason-pfizer monkey virus (mpmv ... | 2002 | 12239296 |
| the mason-pfizer monkey virus internal scaffold domain enables in vitro assembly of human immunodeficiency virus type 1 gag. | the mason-pfizer monkey virus (m-pmv) gag protein possesses the ability to assemble into an immature capsid when synthesized in a reticulocyte lysate translation system. in contrast, the human immunodeficiency virus (hiv) gag protein is incapable of assembly in parallel assays. to enable the assembly of hiv gag, we have combined or inserted regions of m-pmv gag into hiv gag. by both biochemical and morphological criteria, several of these chimeric gag molecules are capable of assembly into immat ... | 2002 | 12368324 |
| close proximity of the mpmv cte to the polyadenylation sequences is important for efficient function in the subgenomic context. | the constitutive transport element (cte) of mason-pfizer monkey virus (mpmv) is a short cis-acting sequence element critical for virus gene expression. analogous to the rev/rev responsive element (rre) of primate lentiviruses, cte allows the nucleocytoplasmic transport of unspliced viral mrnas. in fact, cte can functionally replace rev/rre in the genomic context and has been used successfully in the expression of viral and cellular genes from expression vectors as well. however, unlike rre, cte ... | 2004 | 15351494 |
| proteinases of betaretroviruses bind single-stranded nucleic acids through a novel interaction module, the g-patch. | retroviral proteinases (prs) are essential for retrovirus infectivity but the mechanism of their activity regulation is poorly understood. we investigated possible involvement in this process of the c-terminal domain (ctd) of betaretroviral prs. we found that the presence of ctd attenuates proteolytic activity of mason-pfizer monkey virus pr, while it does not significantly affect the activity of mouse intracisternal a-particle retrovirus pr. however, both prs bind single-stranded nucleic acids ... | 2004 | 15474050 |
| integrase of mason-pfizer monkey virus. | the gene encoding an integrase of mason-pfizer monkey virus (m-pmv) is located at the 3'-end of the pol open reading frame. the m-pmv integrase has not been previously isolated and characterized. we have now cloned, expressed, isolated, and characterized m-pmv integrase and compared its activities and primary structure with those of hiv-1 and other retroviral integrases. m-pmv integrase prefers untranslated 3'-region-derived long-terminal repeat sequences in both the 3'-processing and the strand ... | 2005 | 15634344 |
| localization of self-interacting domains within betaretrovirus gag polyproteins. | the betaretrovirus genus is characterized by the ability to preassemble immature capsids within the cytoplasm. for mason-pfizer monkey virus (m-pmv) this ability depends in part upon the unique internal scaffold domain (isd) within the p12 region of gag. in this study, we have further characterized the ability of m-pmv p12 to promote gag-gag interaction and have examined the gag polyprotein of the related mouse mammary tumor virus (mmtv) to potentially identify a region with equivalent function. ... | 2005 | 15680431 |
| amino acid preferences for a critical substrate binding subsite of retroviral proteases in type 1 cleavage sites. | the specificities of the proteases of 11 retroviruses representing each of the seven genera of the family retroviridae were studied using a series of oligopeptides with amino acid substitutions in the p2 position of a naturally occurring type 1 cleavage site (val-ser-gln-asn-tyr pro-ile-val-gln; the arrow indicates the site of cleavage) in human immunodeficiency virus type 1 (hiv-1). this position was previously found to be one of the most critical in determining the substrate specificity differ ... | 2005 | 15767422 |
| pre-mrna processing enhancer (ppe) elements from intronless genes play additional roles in mrna biogenesis than do ones from intron-containing genes. | most mrna-encoding genes require introns for efficient expression in high eukaryotes. however, mrnas can efficiently accumulate in the cytoplasm without intron excision if they contain cis-acting elements such as the post-transcriptional regulatory element (pre) of hepatitis b virus (hbv), the constitutive transport element (cte) of mason-pfizer monkey virus (mpmv), or the pre-mrna processing enhancer (ppe) of herpes simplex virus' thymidine kinase (hsv-tk) gene. we compared the activities of th ... | 2005 | 15843684 |
| analysis of the contribution of reverse transcriptase and integrase proteins to retroviral rna dimer conformation. | all retroviruses contain two copies of genomic rna that are linked noncovalently. the dimeric rna of human immunodeficiency virus type 1 (hiv-1) undergoes rearrangement during virion maturation, whereby the dimeric rna genome assumes a more stable conformation. previously, we have shown that the packaging of the hiv-1 polymerase (pol) proteins reverse transcriptase (rt) and integrase (in) is essential for the generation of the mature rna dimer conformation. analysis of hiv-1 mutants that are def ... | 2005 | 15858017 |
| assignment of 1h, 13c, and 15n resonances of wt matrix protein and its r55f mutant from mason-pfizer monkey virus. | | 2005 | 15929014 |
| viral interactions with the nuclear transport machinery: discovering and disrupting pathways. | viruses have been invaluable tools for discovering key pathways of nucleocytoplasmic transport. conversely, disruption of specific nuclear transport pathways, are crucial for the productive life cycle of some viruses. the major cellular mrna export pathway, which uses tap (nxf1)/p15(nxt) as receptor, was discovered as a result of tap interaction with cte-containing rnas from mason-pfizer monkey virus. in addition, crm1 or exportin 1, which is a transport receptor that mediates nuclear export of ... | 2005 | 16036565 |
| amino acid residues in the cytoplasmic domain of the mason-pfizer monkey virus glycoprotein critical for its incorporation into virions. | assembly of an infectious retrovirus requires the incorporation of the envelope glycoprotein complex during the process of particle budding. we have recently demonstrated that amino acid substitutions of a tyrosine residue in the cytoplasmic domain block glycoprotein incorporation into budding mason-pfizer monkey virus (m-pmv) particles and abrogate infectivity (c. song, s. r. dubay, and e. hunter, j. virol. 77:5192-5200, 2003). to investigate the contribution of other amino acids in the cytopla ... | 2005 | 16140733 |
| activity of the mason-pfizer monkey virus fusion protein is modulated by single amino acids in the cytoplasmic tail. | mason-pfizer monkey virus (m-pmv) encodes a transmembrane glycoprotein with a 38-amino-acid-long cytoplasmic tail. after the release of the immature virus, a viral protease-mediated cleavage of the cytoplasmic tail (ct) results in the loss of 17 amino acids from the carboxy terminus and renders the envelope protein fusion competent. to investigate the role of individual amino acid residues in the ct in fusion, a series of mutations was introduced, and the effects of these mutations on glycoprote ... | 2005 | 16140734 |
| the rna binding g-patch domain in retroviral protease is important for infectivity and d-type morphogenesis of mason-pfizer monkey virus. | retroviral proteases (prs) cleave the viral polyprotein precursors into functional mature proteins late during particle release and are essential for viral replication. unlike most retroviruses, beta-retroviruses, including mason-pfizer monkey virus (m-pmv), assemble immature capsids within the cytoplasm of the cell. the activation of beta-retroviral proteases must be highly regulated, because processing of the gag-related polyprotein precursors occurs only after transport of immature capsids to ... | 2005 | 16257973 |
| the pp24 phosphoprotein of mason-pfizer monkey virus contributes to viral genome packaging. | the gag protein of mason-pfizer monkey virus, a betaretrovirus, contains a phosphoprotein that is cleaved into the np24 protein and the phosphoprotein pp16/18 during virus maturation. previous studies by yasuda and hunter (j. virology. 1998. 72:4095-4103) have demonstrated that pp16/18 contains a viral late domain required for budding and that the np24 protein plays a role during the virus life cycle since deletion of this n-terminal domain blocked virus replication. the function of the np24 dom ... | 2005 | 16274484 |
| the impact of altered polyprotein ratios on the assembly and infectivity of mason-pfizer monkey virus. | most retroviruses employ a frameshift mechanism during polyprotein synthesis to balance appropriate ratios of structural proteins and enzymes. to investigate the requirements for individual precursors in retrovirus assembly, we modified the polyprotein repertoire of mason-pfizer monkey virus (m-pmv) by mutating the frameshift sites to imitate the polyprotein organization of rous sarcoma virus (gag-pro and gag-pro-pol) or human immunodeficiency virus (gag and gag-pro-pol). for the "rous-like" vir ... | 2009 | 19062065 |
| evolution of primate oncornaviruses: an endogenous virus from langurs (presbytis spp.) with related virogene sequences in other old world monkeys. | gene sequences related to a retrovirus (oncornavirus type d) isolated from a lung cell culture from spectacled langur (presbytis obscurus) are found in multiple copies (20-40 per haploid genome) in langur cellular dna; partially homologous virogene sequences are present in the dna of related old world monkey species. primates thus contain gene sequences for at least two distinct classes of genetically transmitted oncornaviruses, the type c class (isolated from baboons) and the type d class descr ... | 1977 | 16592456 |
| foamy virus capsid assembly occurs at a pericentriolar region through a cytoplasmic targeting/retention signal in gag. | foamy viruses (fv) are unusual retroviruses that differ in many aspects of their life cycle from the orthoretroviruses such as human immunodeficiency virus. similar to mason-pfizer monkey virus (mpmv), fv assemble into capsids intracellularly. the capsids are then transported to a cellular membrane for acquisition of envelope (env) glycoproteins and budding. however, unlike mpmv, budding of fv is dependent upon the presence of env. previous work suggested that fv env proteins are localized to th ... | 2006 | 16749903 |
| nonmyristoylated matrix protein from the mason-pfizer monkey virus forms oligomers. | we studied the oligomeric properties of betaretroviral nonmyristoylated matrix protein (ma) and its r55f mutant from the mason-pfizer monkey virus in solution by means of chemical crosslinking and nmr spectroscopy. by analyzing crosslinked products and using concentration-dependent nmr chemical shift mapping, we have proven that the wild-type (wt) ma forms oligomers in solution. conversely, no oligomerization was observed for the r55f mutant. structural comparison of mas explained their differen ... | 2009 | 19481092 |
| novel engineered hiv-1 east african clade-a gp160 plasmid construct induces strong humoral and cell-mediated immune responses in vivo. | hiv-1 sequences are highly diverse due to the inaccuracy of the viral reverse transcriptase. this diversity has been studied and used to categorize hiv isolates into subtypes or clades, which are geographically distinct. to develop effective vaccines against hiv-1, immunogens representing different subtypes may be important for induction of cross-protective immunity, but little data exist describing and comparing the immunogenicity induced by different subtype-based vaccines. this issue is furth ... | 2003 | 14517067 |
| cross-packaging of genetically distinct mouse and primate retroviral rnas. | the mouse mammary tumor virus (mmtv) is unique from other retroviruses in having multiple viral promoters, which can be regulated by hormones in a tissue specific manner. this unique property has lead to increased interest in studying mmtv replication with the hope of developing mmtv based vectors for human gene therapy. however, it has recently been reported that related as well as unrelated retroviruses can cross-package each other's genome raising safety concerns towards the use of candidate ... | 2009 | 19602292 |
| distinct roles for nucleic acid in in vitro assembly of purified mason-pfizer monkey virus canc proteins. | in contrast to other retroviruses, mason-pfizer monkey virus (m-pmv) assembles immature capsids in the cytoplasm. we have compared the ability of minimal assembly-competent domains from m-pmv and human immunodeficiency virus type 1 (hiv-1) to assemble in vitro into virus-like particles in the presence and absence of nucleic acids. a fusion protein comprised of the capsid and nucleocapsid domains of gag (canc) and its n-terminally modified mutant (deltaprocanc) were used to mimic the assembly of ... | 2006 | 16809314 |
| an intron with a constitutive transport element is retained in a tap messenger rna. | alternative splicing is a key factor contributing to genetic diversity and evolution. intron retention, one form of alternative splicing, is common in plants but rare in higher eukaryotes, because messenger rnas with retained introns are subject to cellular restriction at the level of cytoplasmic export and expression. often, retention of internal introns restricts the export of these mrnas and makes them the targets for degradation by the cellular nonsense-mediated decay machinery if they conta ... | 2006 | 16971948 |