Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.1 (S1 nuclease)
 3,660 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The requirement for tnv, a tat-env-rev fusion protein expressed by the IIIB strain of HIV-1, was tested. The expression of tnv was prevented by altering the 5' splice site that flanks the central coding exon of tnv. Mutants that carry such an altered 5' splice site replicate normally in an established T-cell line and in peripheral blood lymphocytes, demonstrating that tnv has no effect on virus replication. However, two mutants that carry an alteration in the 3' splice site of the same exon are replication defective. The 3' splice site mutations result in significant reduction in the expression of the 16-kDa tat protein and induce the expression of large amounts of a 19-kDa rev-related protein that initiates within the central coding exon of tnv. S1 nuclease analysis reveals that splicing to the central tnv exon occurs with substantially increased efficiency via the use of an alternate 3' splice site six nucleotides 3' from the mutated site. The effect of the 3' splice site mutations on viral protein expression and replication are fully reversed by a second site mutation that eliminates the alternate splice site.
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PMID:The role of the tnv protein and tnv RNA splicing signals in replication of HIV-1 IIIB isolates. 164 82

Mapping of transcripts of the human foamy virus genome was carried out in permissive human embryonic fibroblast cells by Northern blot hybridization and S1 nuclease analysis. Since several splice sites that are localized within a relatively narrow genomic region were detected, the polymerase chain reaction (PCR) was employed, and cloning and sequencing of the splice site junctions of the corresponding viral cDNAs were subsequently performed. All spumavirus transcripts have a common but relatively short leader RNA. Genomic, singly spliced env mRNAs and several singly and multiply spliced subgenomic transcripts were identified. The multiply spliced viral mRNAs consist of various exons located in the central or 3' part of the viral genome. At least four novel gene products, termed Bet, Bes, Beo, and Bel3, are predicted to exist. The poly(A) addition site that defines the boundary of the R and U5 region in the 3' long terminal repeat was determined. The pattern of spumavirus splicing is more complex than that of oncoviruses and more similar to that of lentiviruses. One of the characteristic features of spumavirus transcription is the existence of singly spliced bel1 and bel2 mRNAs that alternatively are multiply spliced, thereby generating a complexity comparable to, but different from, that of lentiviruses and from that of other known retroviruses. The complex spumavirus transcriptional pattern of human spumavirus and the coding potential of the 10 exons identified are discussed.
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PMID:Analysis of splicing patterns of human spumaretrovirus by polymerase chain reaction reveals complex RNA structures. 184 94

The nef gene is conserved among all human and simian lentiviruses. However, the amino acid similarity between simian immunodeficiency virus (SIV) and human immunodeficiency virus type 1 NEF is only 38%. To assess the role of SIV NEF on virus replication and compare its activity with that of its human immunodeficiency virus type 1 counterpart, we examined the activity of an intact nef gene from proviral clone pSIV 102, an isolate from SIV-MAC-251-infected cells. Proviral clone pSIV BA was constructed by introducing a premature termination codon at codon 40 of the nef gene without altering the predicted amino acid sequence of the overlapping env gene. These two clones were transfected into CD4- COS cells, and virus replication was monitored by p27 enzyme-linked immunosorbent assay kits. In seven independent experiments, clone pSIV BA afforded two- to sixfold greater levels of viral antigen compared with those in clone pSIV 102 and two- to sixfold-increased levels of viral mRNAs as indicated with Northern (RNA) blot and S1 nuclease protection analyses. Nuclear run-on assays demonstrated a two- to threefold increased rate of RNA synthesis with nuclei isolated from cells transfected with pSIV BA compared with that from cells transfected with pSIV 102. In contrast, there was no apparent destabilization of SIV mRNAs by NEF, as measured in dactinomycin-treated cells. This study demonstrates that SIV NEF is a negative regulator of virus replication and acts by suppressing the level of mRNA synthesis and accumulation in COS cells.
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PMID:Simian immunodeficiency virus negative factor suppresses the level of viral mRNA in COS cells. 204 Oct 81

Rev is an essential regulatory protein of the human immunodeficiency virus type 1 (HIV-1) that affects the transport and half-life of certain viral mRNAs. Rev exerts its function via a unique element, the Rev-responsive element (RRE), located within the env region of HIV-1. It has been previously demonstrated that Rev affects the relative levels of RRE-containing and RRE-lacking mRNAs. We have studied the effects of Rev on the expression of the three different groups of small, multiply spliced mRNAs that lack the RRE sequence and encode the regulatory proteins Tat, Rev, and Nef. To monitor the tat, rev, and nef mRNAs we generated specific S1 nuclease mapping probes that distinguish among them. Analysis of all the mRNA species producing Tat, Rev, and Nef revealed that their levels are coordinately regulated by Rev. They are increased in the absence of Rev protein and are down regulated in the presence of Rev. The corresponding proteins were measured by immunoprecipitations, and their levels are in agreement with the RNA levels. These results verify the model proposing that Rev is a general regulator indirectly affecting all the multiply spliced mRNAs to a similar extent. Therefore, Rev down regulates its own expression and the expression of Tat and Nef.
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PMID:Feedback regulation of human immunodeficiency virus type 1 expression by the Rev protein. 219 81

We examined the mos-specific intracellular RNA species in 6m2 cells, an NRK cell line nonproductively infected with the ts110 mutant of Moloney murine sarcoma virus. These cells present a normal phenotype at 39 degrees C and a transformed phenotype at 28 or 33 degrees C, expressing two viral proteins, termed P85gag-mos and P58gag, at 28 to 33 degrees C, whereas only P58gag is expressed at 39 degrees C. It has been previously shown that 6m2 cells contain two virus-specific RNA species, a 4.0-kilobase (kb) RNA coding for P58gag and a 3.5-kb RNA coding for P85gag-mos. Using both Northern blot and S1 nuclease analyses, we show here that the 3.5-kb RNA is the predominant viral RNA species in 6m2 cells grown at 28 degrees C, whereas only the 4.0-kb RNA is detected at 39 degrees C. During temperature shift experiments, the 3.5-kb RNA species disappears after a shift from 28 to 39 degrees C and is detected again after a shift back from 39 to 28 degrees C. By Southern blot analysis, we have detected only one ts110 proviral DNA in the 6m2 genome. This observation, as well as previously published heteroduplex and S1 nuclease analyses which showed that the 3.5-kb RNA species lacks about 430 bases found at the gag gene-mos gene junction in the 4.0-kb RNA, suggests that the 3.5-kb RNA is a splicing product of the 4.0-kb RNA. The absence of the 3.5-kb RNA when 6m2 cells are grown at 39 degrees C indicates that the splicing reaction is thermosensitive. The splicing defect of the ts110 Moloney murine sarcoma virus viral RNA in 6m2 cells cannot be complemented by acute Moloney murine leukemia virus superinfection, since no 3.5-kb ts110 RNA was detected in acutely superinfected 6m2 cells maintained at 39 degrees C. The spliced Moloney murine leukemia virus env mRNA, however, is found in acutely infected cells maintained at 39 degrees C, suggesting that the lack of ts110 viral RNA splicing at 39 degrees C is not due to an obvious host defect. In sharp contrast, however, 6m2 cells chronically superinfected with Moloney murine leukemia virus produce a 3.5-kb RNA species at 39 degrees C as well as at 28 degrees C and contain proviral DNAs corresponding to the two viral RNA species.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Temperature-sensitive viral RNA expression in Moloney murine sarcoma virus ts110-infected cells. 298 39

Large deletion (LD) mutants of Prague strain Rous sarcoma virus, subgroup B (PrB), derived by serial undiluted passage through chicken (C/E) cells, were isolated and characterized. Individual LD viruses were initially isolated by cloning in soft agar of infected, chemically transformed quail (QT6) cells. Two regions of the PrB genome were deleted in the formation of the LD virus. This resulted in the junction of gag sequences in p12 to env sequences in gp37, and in the loss of the src gene. DNA restriction analysis of biologically active lambda Charon 27-LD recombinant clones indicated that individual LD viruses contained similar but not identical deletion endpoints. Two LD isolates, LD25 and LD85, were further subcloned into pBR322, and the deletion junctions were examined by DNA sequencing. Although the gag-env deletion endpoints were identical in the two subclones, heterogeneity was observed across the src deletion in that both mutants analyzed had the same 5' endpoint but slightly different 3' endpoints. In all cases, only a single homologous base (always an A residue) was found at the deletion endpoint. S1 nuclease analysis of the RNA from a number of QT6-LD clones gave similar results, indicating that the LD population was composed of viruses with similar but not identical deletion endpoints. Such viruses may have been generated from errors during reverse transcription of the virion RNA with subsequent selection assuring their dominance in the population.
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PMID:Evolutionary variants of Rous sarcoma virus: large deletion mutants do not result from homologous recombination. 298 61

The human T-cell leukemia viruses (HTLV) are replication-competent retroviruses whose genomes contain gag, pol, and env genes as well as a fourth gene, termed x, which is believed to be the transforming gene of HTLV. The product of the x gene is now shown to be encoded by a 2.1-kilobase messenger RNA derived by splicing of at least two introns. By means of S1 nuclease mapping of this RNA and nucleic acid sequence analysis of a complementary DNA clone, the complete primary structure of the x-gene product has been determined. It is encoded by sequences containing the env initiation codon and one nucleotide of the next codon spliced to the major open reading frame of the HTLV-I and HTLV-II x gene.
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PMID:HTLV x-gene product: requirement for the env methionine initiation codon. 299 32

The subgenomic mRNA's of Rous sarcoma virus share a common 5' leader sequence spliced from genomic RNA. We have examined the 5' terminal sequences of four Rous sarcoma virus RNAs: virion RNA and three species of intracellular mRNA which direct the synthesis of the RSV gene products. The lengths of the leaders on the RNAs were determined by the extent that they could protect cloned Rous sarcoma virus DNA fragments from S1 nuclease digestion after RNA-DNA hybridization. We found that the subgenomic mRNA's that direct the synthesis of the env and src gene products have uninterrupted spliced leader sequences of approximately 390 nucleotides, whereas virion RNA and full-length intracellular viral RNA have 5' termini homologous to the cloned viral DNA probe over at least the first 735 bases. In the accompanying manuscript we have determined the nucleotide sequence of the 5' end of the Rous sarcoma virus genome, including the candidate splice donor site identified here (Swanstrom et al., J. Virol. 41:535-541, 1982).
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PMID:The leader sequence of the subgenomic mRNA's of Rous sarcoma virus is approximately 390 nucleotides. 628 64

The human foamy or spumaretrovirus (HSRV) is a complex retrovirus that encodes the three retroviral genes gag, pol, and env and, in addition, at least three bel genes. The HSRV Bel-1 protein was identified as a transcriptional trans-activator. HSRV transcription starts in the 5' long terminal repeat at a defined guanine residue. We report here that a second efficiently utilized start site of transcription is contained within a HSRV env DNA sequence upstream of the bel genes. Bel-specific transcripts that initiate at the internal transcriptional start site at nt 9196 were identified in HSRV-infected cells by primer extension and S1 nuclease analysis, and the intragenic promoter was shown to be constitutively activated by Bel-1 in the HSRV provirus. In transient expression assays with indicator gene constructs, expression by the HSRV intragenic promoter/enhancer is Bel-1 dependent. The data provide evidence for an intragenic start site of transcription in the genome of a complex, exogenous human retrovirus and are discussed in terms of a model for regulating spumaretroviral gene expression.
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PMID:Human foamy virus genome possesses an internal, Bel-1-dependent and functional promoter. 839 17