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Abstract
The topological state of DNA may play a role in regulating chromatin structure and gene expression in eucaryotes. To test this hypothesis, the arrangements of nucleosomes on circular and unit-length linear simian virus 40 (SV40) DNAs incubated in nuclei of Xenopus oocytes were determined by (i) analyzing changes in the electrophoretic properties of the DNAs and (ii) examining the patterns of DNA fragments resulting from digestions with micrococcal nuclease. Whereas circular DNA became associated with nucleosomes that were arranged along the DNA at regular intervals of approximately 195 base pairs, linear DNA failed to reconstitute into chromatin containing regularly spaced nucleosomes. DNA that failed to form proper chromatin was gradually degraded, indicating that histone proteins in proper association with DNA may be the cellular component that normally protects chromosomal DNA from endonucleolytic attack. When either circular or linear DNA was incubated in an in vitro transcription system made from a whole-cell extract of HeLa cells, most of the molecules did not associate with histone proteins to form regularly spaced nucleosomes. Furthermore, linearization of mRNA-encoding DNAs, including SV40, reduces their transcriptional activity in Xenopus oocytes to a level comparable to that obtained with the in vitro transcription system employed here. Therefore, proper association of DNA with appropriate cellular chromosomal factors may be a prerequisite for proper transcription by RNA polymerase II.
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Affiliation(s)
- J E Mertz
- McArdle Laboratory for Cancer Research, University of Wisconsin, Madison, Wisconsin 53706, USA
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2
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Abstract
The topological state of DNA may play a role in regulating chromatin structure and gene expression in eucaryotes. To test this hypothesis, the arrangements of nucleosomes on circular and unit-length linear simian virus 40 (SV40) DNAs incubated in nuclei of Xenopus oocytes were determined by (i) analyzing changes in the electrophoretic properties of the DNAs and (ii) examining the patterns of DNA fragments resulting from digestions with micrococcal nuclease. Whereas circular DNA became associated with nucleosomes that were arranged along the DNA at regular intervals of approximately 195 base pairs, linear DNA failed to reconstitute into chromatin containing regularly spaced nucleosomes. DNA that failed to form proper chromatin was gradually degraded, indicating that histone proteins in proper association with DNA may be the cellular component that normally protects chromosomal DNA from endonucleolytic attack. When either circular or linear DNA was incubated in an in vitro transcription system made from a whole-cell extract of HeLa cells, most of the molecules did not associate with histone proteins to form regularly spaced nucleosomes. Furthermore, linearization of mRNA-encoding DNAs, including SV40, reduces their transcriptional activity in Xenopus oocytes to a level comparable to that obtained with the in vitro transcription system employed here. Therefore, proper association of DNA with appropriate cellular chromosomal factors may be a prerequisite for proper transcription by RNA polymerase II.
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3
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Miller TJ, Mertz JE. Template structural requirements for transcription in vivo by RNA polymerase II. Mol Cell Biol 2003; 2:1595-607. [PMID: 14582200 PMCID: PMC369967 DOI: 10.1128/mcb.2.12.1595-1607.1982] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Purified simian virus 40 (SV40) DNA is reconstituted into chromatin and transcribed by endogenous RNA polymerase II when microinjected into nuclei of Xenopus laevis oocytes. We have correlated the kinetics of chromatin reconstitution with that of accumulation of virus-specific RNA in this system. A delay of approximately 3 h was found in the appearance of appreciable numbers of both fully supercoiled molecules and transcriptionally active templates. SV40 mini-chromosomes, isolated from virus-infected monkey cells with 0.2 M NaCl, also exhibited this lag in onset of transcriptional activity when microinjected into oocytes. These findings indicate that neither purified SV40 DNA nor SV40 DNA containing a full complement of nucleosomes can function as a template for transcription in vivo before association with appropriate cellular nonhistone chromosomal factors has taken place. In addition, the gradual degradation of linear SV40 DNA in oocytes was not sufficient to account for the fact that it was much less transcriptionally active than circular SV40 DNA. Taken together, these results indicate that the conformational state of the DNA can affect its ability to function as a template for transcription in vivo by RNA polymerase II. In contrast, transcription by RNA polymerase III of purified, circularized cloned DNAs encoding genes for 5S rRNA was detectable long before the injected DNAs had time to reconstitute into chromatin. Therefore, the template structural requirements for transcription in vivo by RNA polymerases II and III are different.
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Affiliation(s)
- T J Miller
- McArdle Laboratory for Cancer Research, University of Wisconsin, Madison, Wisconsin 53706, USA
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4
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Abstract
Purified simian virus 40 (SV40) DNA is reconstituted into chromatin and transcribed by endogenous RNA polymerase II when microinjected into nuclei of Xenopus laevis oocytes. We have correlated the kinetics of chromatin reconstitution with that of accumulation of virus-specific RNA in this system. A delay of approximately 3 h was found in the appearance of appreciable numbers of both fully supercoiled molecules and transcriptionally active templates. SV40 mini-chromosomes, isolated from virus-infected monkey cells with 0.2 M NaCl, also exhibited this lag in onset of transcriptional activity when microinjected into oocytes. These findings indicate that neither purified SV40 DNA nor SV40 DNA containing a full complement of nucleosomes can function as a template for transcription in vivo before association with appropriate cellular nonhistone chromosomal factors has taken place. In addition, the gradual degradation of linear SV40 DNA in oocytes was not sufficient to account for the fact that it was much less transcriptionally active than circular SV40 DNA. Taken together, these results indicate that the conformational state of the DNA can affect its ability to function as a template for transcription in vivo by RNA polymerase II. In contrast, transcription by RNA polymerase III of purified, circularized cloned DNAs encoding genes for 5S rRNA was detectable long before the injected DNAs had time to reconstitute into chromatin. Therefore, the template structural requirements for transcription in vivo by RNA polymerases II and III are different.
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5
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Wu ZA, Murphy C, Callan HG, Gall JG. Small nuclear ribonucleoproteins and heterogeneous nuclear ribonucleoproteins in the amphibian germinal vesicle: loops, spheres, and snurposomes. J Cell Biol 1991; 113:465-83. [PMID: 1826687 PMCID: PMC2288976 DOI: 10.1083/jcb.113.3.465] [Citation(s) in RCA: 159] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We have examined the distribution of snRNPs in the germinal vesicle (GV) of frogs and salamanders by immunofluorescent staining and in situ nucleic acid hybridization. The major snRNAs involved in pre-mRNA splicing (U1, U2, U4, U5, and U6) occur together in nearly all loops of the lampbrush chromosomes, and in hundreds to thousands of small granules (1-4 microns diameter) suspended in the nucleoplasm. The loops and granules also contain several antigens that are regularly associated with snRNAs or spliceosomes (the Sm antigen, U1- and U2-specific antigens, and the splicing factor SC35). A second type of granule, often distinguishable by morphology, contains only U1 snRNA and associated antigens. We propose the term "snurposome" to describe the granules that contain snRNPs ("snurps"). Those that contain only U1 snRNA are A snurposomes, whereas those that contain all the splicing snRNAs are B snurposomes. GVs contain a third type of snRNP granule, which we call the C snurposome. C snurposomes range in size from less than 1 micron to giant structures greater than 20 microns in diameter. Usually, although not invariably, they have B snurposomes on their surface. They may also contain from one to hundreds of inclusions. Because of their remarkably spherical shape, C snurposomes with their associated B snurposomes have long been referred to as spheres or sphere organelles. Most spheres are free in the nucleoplasm, but a few are attached to chromosomes at specific chromosome loci, the sphere organizers (SOs). The relationship of sphere organelles to other snRNP-containing structures in the GV is obscure. We show by immunofluorescent staining that the lampbrush loops and B snurposomes also react with antibodies against heterogeneous nuclear ribonucleoproteins (hnRNPs). Transcription units on the loops are uniformly stained by anti-hnRNP and anti-snRNP antibodies, suggesting that nascent transcripts are associated with hnRNPs and snRNPs along their entire length, perhaps in the form of a unitary hnRNP/snRNP particle. That B snurposomes contain so many components involved in pre-mRNA packaging and processing suggests that they may serve as sites for assembly and storage of hnRNP/snRNP complexes destined for transport to the nascent transcripts on the lampbrush chromosome loops.
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Affiliation(s)
- Z A Wu
- Department of Embryology, Carnegie Institution, Baltimore, Maryland 21210
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6
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Pan ZQ, Ge H, Fu XY, Manley JL, Prives C. Oligonucleotide-targeted degradation of U1 and U2 snRNAs reveals differential interactions of simian virus 40 pre-mRNAs with snRNPs. Nucleic Acids Res 1989; 17:6553-68. [PMID: 2550896 PMCID: PMC318349 DOI: 10.1093/nar/17.16.6553] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We have investigated the roles of U1 and U2 snRNP particles in SV40 pre-mRNA splicing by oligonucleotide-targeted degradation of U1 or U2 snRNAs in Xenopus laevis oocytes. Microinjection of oligonucleotides complementary to regions of U1 or U2 RNAs either in the presence or absence of SV40 DNA resulted in specific cleavage of the corresponding snRNA. Unexpectedly, degradation of U1 or U2 snRNA was far more extensive when the oligonucleotide was injected without, or prior to, introduction of viral DNA. In either co-injected or pre-injected oocytes, these oligonucleotides caused a dramatic reduction in the accumulation of spliced SV40 mRNA expressed from the viral late region, and a commensurate increase in unspliced late RNA. When pre-injected, two different U2 specific oligonucleotides also inhibited the formation of both large and small tumor antigen spliced early mRNAs. However, even when, by pre-injection of a U1 5' end-specific oligonucleotide, greater than 95% degradation of the U1 snRNA 5' ends occurred in oocytes, no reduction in early pre-mRNA splicing was observed. In contrast, the same U1 5' end oligonucleotide, when added to HeLa splicing extracts, substantially inhibited the splicing of SV40 early pre-mRNA, indicating that U1 mRNP is not totally dispensable for early splicing. These findings confirm and extend our earlier observations which suggested that different pre-mRNAs vary in their requirements for snRNPs.
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Affiliation(s)
- Z Q Pan
- Department of Biological Sciences, Columbia University, New York, NY 10027
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7
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Christianson KK, Ingersoll JD, Landon RM, Pfeiffer NE, Gerber JD. Characterization of a temperature sensitive feline infectious peritonitis coronavirus. Arch Virol 1989; 109:185-96. [PMID: 2558634 PMCID: PMC7086852 DOI: 10.1007/bf01311080] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/1989] [Accepted: 09/20/1989] [Indexed: 01/01/2023]
Abstract
The characteristics of a temperature sensitive feline infectious peritonitis virus (TS-FIPV) were examined. TS-FIPV, unlike its parent strain, DF2 wild type FIPV (WT-FIPV), propagated at 31 degrees C (permissive temperature) but not at 39 degrees C (nonpermissive temperature). This temperature preference of TS-FIPV was also demonstrated in cats by the ability of the virus to replicate only at the lower temperature in the upper respiratory tract and not at systemic sites where higher temperatures (38-39 degrees C) prevail. Viral structural proteins and RNA were synthesized at 39 degrees C but some undefined maturational defect prevented the formation of infectious TS-FIPV at its nonpermissive temperature. TS-FIPV was more thermolabile than WT-FIPV which indicated alterations in the structural proteins of TS-FIPV, and a difference in the envelope protein of the two viruses was revealed by Western blot analysis. Plaque assay characterization showed that TS-FIPV produced small plaques in comparison to the large plaques of WT-FIPV. These unique characteristics possessed by TS-FIPV may account for its nonvirulent nature and ability to stimulate protective immune responses in cats.
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Affiliation(s)
- K K Christianson
- Biological Research and Development, Norden Laboratories, Lincoln, Nebraska
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8
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Koltunow AM, Gregg K, Rogers GE. Promoter efficiency depends upon intragenic sequences. Nucleic Acids Res 1987; 15:7795-807. [PMID: 2444923 PMCID: PMC306308 DOI: 10.1093/nar/15.19.7795] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Experiments concerning gene transcription in Xenopus oocytes have revealed that the efficiency of the HSV-TK promoter is dependent upon the nature of the attached gene sequences. Transcriptional efficiency of the TK promoter when attached to its own gene was 30-fold higher than that observed when the promoter was attached either to an avian keratin gene or to the chicken histone H2B gene. Furthermore, attachment of the keratin gene promoter to the TK gene resulted in a 20-fold increase in keratin promoter efficiency. It was found by subsequent experiments that the TK gene is able to exert a stimulatory influence upon attached promoter sequences. This cis effect was shown to be independent of orientation but dependent upon the distance between the DNA sequences involved.
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Affiliation(s)
- A M Koltunow
- Department of Biochemistry, University of Adelaide, SA, Australia
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9
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Michaeli T, Prives C. pBR322 DNA inhibits simian virus 40 gene expression in Xenopus laevis oocytes. Nucleic Acids Res 1987; 15:1579-94. [PMID: 3029720 PMCID: PMC340568 DOI: 10.1093/nar/15.4.1579] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
SV40 DNA form I is expressed efficiently after its injection into the nuclei of Xenopus laevis oocytes, resulting in the synthesis of RNA and protein products of both viral late and early transcription units. However it was observed that injection of SV40 genes cloned into pBR322 or related plasmids yielded vastly reduced quantities of viral DNA and proteins. If SV40 DNA was cleaved from the plasmid, and then recircularized prior to microinjection, viral expression was regained. The inhibition by plasmid DNA was not confined to an effect in cis because coinjection of circular pBR322 DNA along with SV40 DNA, as separate entities, also blocked viral RNA and protein synthesis. As circular but not linear pBR322 DNA was actively transcribed by polymerase II in oocytes, even in the presence of SV40 DNA, it is likely that pBR322 competes for transcription factors required for viral gene expression. Injection of pBR322 as early as two hours after injection of SV40 DNA into the oocyte nucleus did not inhibit SV40 RNA synthesis, indicating that once initiated, SV40 transcription is stable and insensitive to the competition by plasmid DNA. A plasmid vector was developed that allows expression of SV40 DNA in Xenopus laevis oocytes.
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10
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Abstract
Expression of the simian virus 40 (SV40) early and late regions was examined in Xenopus laevis oocytes microinjected with viral DNA. In contrast to the situation in monkey cells, both late-strand-specific (L-strand) RNA and early-strand-specific (E-strand) RNA could be detected as early as 2 h after injection. At all time points tested thereafter, L-strand RNA was synthesized in excess over E-strand RNA. Significantly greater quantities of L-strand, relative to E-strand, RNA were detected over a 100-fold range of DNA concentrations injected. Analysis of the subcellular distribution of [35S]methionine-labeled viral proteins revealed that while the majority of the VP-1 and all detectable small t antigen were found in the oocyte cytoplasm, most of the large T antigen was located in the oocyte nucleus. The presence of the large T antigen in the nucleus led us to investigate whether this viral product influences the relative synthesis of late or early RNA in the oocyte as it does in infected monkey cells. Microinjection of either mutant C6 SV40 DNA, which encodes a large T antigen unable to bind specifically to viral regulatory sequences, or deleted viral DNA lacking part of the large T antigen coding sequences yielded ratios of L-strand to E-strand RNA that were similar to those observed with wild-type SV40 DNA. Taken together, these observations suggest that the regulation of SV40 RNA synthesis in X. laevis oocytes occurs by a fundamentally different mechanism than that observed in infected monkey cells. This notion was further supported by the observation that the major 5' ends of L-strand RNA synthesized in oocytes were different from those detected in infected cells. Furthermore, only a subset of those L-strand RNAs were polyadenylated.
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11
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Lanoix J, Tseng RW, Acheson NH. Duplication of functional polyadenylation signals in polyomavirus DNA does not alter efficiency of polyadenylation or transcription termination. J Virol 1986; 58:733-42. [PMID: 2871197 PMCID: PMC252978 DOI: 10.1128/jvi.58.3.733-742.1986] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
We constructed viable insertion mutants of polyomavirus that contain duplications of the nucleotide sequences surrounding the polyadenylation sites for both E- and L-strand RNAs. Our results showed that formation of poly(A)+ 3'termini of L-strand mRNAs requires sequence elements located between 12 and 87 nucleotides downstream of AAUAAA. No more than 19 nucleotides upstream and 44 nucleotides downstream of AAUAAA are required for polyadenylation of E-strand mRNAs. Our results and those of others suggest that there are three distinct sequence elements required for mRNA 3' end formation: AAUAAA and two downstream elements. An insertion mutant containing two adjacent functional polyadenylation signals produced E-strand and L-strand mRNAs with 3' ends at both sites. However, the overall level of polyadenylation of L-strand RNAs was not increased over the low (10 to 25%) levels seen with wild-type virus. Neither was the efficiency of termination of L-strand transcription increased in mutant virus-infected cells. We conclude that factors required for both polyadenylation and transcription termination are limiting in polyomavirus-infected mouse cells.
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12
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Abstract
Expression of the simian virus 40 (SV40) early and late regions was examined in Xenopus laevis oocytes microinjected with viral DNA. In contrast to the situation in monkey cells, both late-strand-specific (L-strand) RNA and early-strand-specific (E-strand) RNA could be detected as early as 2 h after injection. At all time points tested thereafter, L-strand RNA was synthesized in excess over E-strand RNA. Significantly greater quantities of L-strand, relative to E-strand, RNA were detected over a 100-fold range of DNA concentrations injected. Analysis of the subcellular distribution of [35S]methionine-labeled viral proteins revealed that while the majority of the VP-1 and all detectable small t antigen were found in the oocyte cytoplasm, most of the large T antigen was located in the oocyte nucleus. The presence of the large T antigen in the nucleus led us to investigate whether this viral product influences the relative synthesis of late or early RNA in the oocyte as it does in infected monkey cells. Microinjection of either mutant C6 SV40 DNA, which encodes a large T antigen unable to bind specifically to viral regulatory sequences, or deleted viral DNA lacking part of the large T antigen coding sequences yielded ratios of L-strand to E-strand RNA that were similar to those observed with wild-type SV40 DNA. Taken together, these observations suggest that the regulation of SV40 RNA synthesis in X. laevis oocytes occurs by a fundamentally different mechanism than that observed in infected monkey cells. This notion was further supported by the observation that the major 5' ends of L-strand RNA synthesized in oocytes were different from those detected in infected cells. Furthermore, only a subset of those L-strand RNAs were polyadenylated.
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13
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Kinetics and efficiency of polyadenylation of late polyomavirus nuclear RNA: generation of oligomeric polyadenylated RNAs and their processing into mRNA. Mol Cell Biol 1984. [PMID: 6325893 DOI: 10.1128/mcb.4.4.722] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The rate and efficiency of polyadenylation of late polyomavirus RNA in the nucleus of productively infected mouse kidney cells were determined by measuring incorporation of [3H]uridine into total and polyadenylated viral RNAs fractionated by oligodeoxythymidylic acid-cellulose chromatography. Polyadenylation is rapid: the average delay between synthesis and polyadenylation of viral RNA in the nucleus is 1 to 2 min. However, only 10 to 25% of viral RNA molecules become polyadenylated. Polyadenylated RNAs in the nucleus are a family of molecules which differ in size by an integral number of viral genome lengths (5.3 kilobases). These RNAs are generated by repeated passage of RNA polymerase around the circular viral DNA, accompanied by addition of polyadenylic acid to a unique 3' end situated 2.2 + n(5.3) kilobases from the 5' end of the RNAs (n can be an integer from 0 to at least 3). Between 30 and 50% of the sequences in nuclear polyadenylated RNA are conserved during processing and transport to the cytoplasm as mRNA. This is consistent with the molar ratios of nuclear polyadenylated RNAs in the different size classes, and it suggests that most polyadenylated nuclear RNA is efficiently processed to mRNA. Thus, the low overall conservation of viral RNA sequences between nucleus and cytoplasm is explained by (i) low efficiency of polyadenylation of nuclear RNA and (ii) removal of substantial parts of polyadenylated RNAs during splicing. The correlation between inefficient termination of transcription and inefficient polyadenylation of transcripts suggests that these two events may be causally linked.
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14
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Acheson NH. Kinetics and efficiency of polyadenylation of late polyomavirus nuclear RNA: generation of oligomeric polyadenylated RNAs and their processing into mRNA. Mol Cell Biol 1984; 4:722-9. [PMID: 6325893 PMCID: PMC368788 DOI: 10.1128/mcb.4.4.722-729.1984] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The rate and efficiency of polyadenylation of late polyomavirus RNA in the nucleus of productively infected mouse kidney cells were determined by measuring incorporation of [3H]uridine into total and polyadenylated viral RNAs fractionated by oligodeoxythymidylic acid-cellulose chromatography. Polyadenylation is rapid: the average delay between synthesis and polyadenylation of viral RNA in the nucleus is 1 to 2 min. However, only 10 to 25% of viral RNA molecules become polyadenylated. Polyadenylated RNAs in the nucleus are a family of molecules which differ in size by an integral number of viral genome lengths (5.3 kilobases). These RNAs are generated by repeated passage of RNA polymerase around the circular viral DNA, accompanied by addition of polyadenylic acid to a unique 3' end situated 2.2 + n(5.3) kilobases from the 5' end of the RNAs (n can be an integer from 0 to at least 3). Between 30 and 50% of the sequences in nuclear polyadenylated RNA are conserved during processing and transport to the cytoplasm as mRNA. This is consistent with the molar ratios of nuclear polyadenylated RNAs in the different size classes, and it suggests that most polyadenylated nuclear RNA is efficiently processed to mRNA. Thus, the low overall conservation of viral RNA sequences between nucleus and cytoplasm is explained by (i) low efficiency of polyadenylation of nuclear RNA and (ii) removal of substantial parts of polyadenylated RNAs during splicing. The correlation between inefficient termination of transcription and inefficient polyadenylation of transcripts suggests that these two events may be causally linked.
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15
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Ernoult-Lange M, May P, Moreau P, May E. Simian virus 40 late promoter region able to initiate simian virus 40 early gene transcription in the absence of the simian virus 40 origin sequence. J Virol 1984; 50:163-73. [PMID: 6321788 PMCID: PMC255596 DOI: 10.1128/jvi.50.1.163-173.1984] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
To improve our knowledge of the simian virus 40 (SV40) late promoter control region, we took advantage of the fact that T antigen can be expressed with a heterologous promoter. We constructed three chimeric plasmids (pEMP-273, pEMP-LCAP-162, and pEMP-LCAP-113) each with a putative late promoter sequence positioned immediately upstream from the SV40 early gene coding region but in an orientation opposite to its natural orientation in the SV40 genome. After transfection of the recombinant DNA into HeLa or CV1 cells, T antigen accumulation, as scored by indirect immunofluorescence, was used as a functional test for promoter activity. We found that the sequence mapping from nucleotides 332 to 273 is not sufficient for promoting transcription of SV40 early gene but does potentiate the promoter activity of the 72-base-pair repeats in initiating the transcription at natural late cap sites. Considering that both plasmids pEMP-LCAP-162 and pEMP-LCAP-113 lack all of the sequence of the SV40 replication origin, we conclude that SV40 transcription can be mediated through a putative late promoter in the absence of the sequence for the SV40 replication origin.
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16
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Regulation of adenovirus transcription by an E1a gene in microinjected Xenopus laevis oocytes. Mol Cell Biol 1984. [PMID: 6318084 DOI: 10.1128/mcb.3.12.2131] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The regulation of adenovirus type 5 gene expression by the E1a gene product was examined in microinjected Xenopus laevis oocytes. Chimeric genes were constructed which included the promoter region of early adenovirus type 5 gene 3 and the structural sequence which codes for the bacterial enzyme chloramphenicol-3-O-acetyltransferase (CAT). A plasmid containing this chimeric gene as well as plasmids containing the E1a gene were coinjected into oocyte nuclei. The presence of the E1a gene was shown to increase CAT activity by up to 8.5-fold over basal levels. Synthesis of the functional product from the E1a gene requires the removal of intron sequences by RNA splicing. The E1a gene and a derivative that precisely lacks the intron were equally effective in increasing CAT activity, suggesting that splicing of the primary E1a transcript is efficiently accomplished in the oocyte nucleus. This was confirmed by directly examining the E1a mRNAs by the S1 mapping procedure. A protein extract from adenovirus type 5-infected HeLa cells enriched for the E1a protein may supplant the E1a plasmid in enhancing CAT activity. Synthesis of the CAT enzyme after gene injection is invariant in oocytes from the same frog, but oocytes from different frogs show a high degree of variability in their ability to synthesize the CAT enzyme. Microinjected X. laevis oocytes appear to be an extremely useful system to study the effects of protein elements on transcription.
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17
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McStay B, Bird A. The origin of the rRNA precursor from Xenopus borealis, analysed in vivo and in vitro. Nucleic Acids Res 1983; 11:8167-81. [PMID: 6324076 PMCID: PMC326573 DOI: 10.1093/nar/11.23.8167] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We have determined the origin of the major transcript of Xenopus borealis rDNA by the use of an SI nuclease protection assay. The DNA surrounding the origin of this transcript was sequenced, and the region upstream of the origin was shown to have strong sequence homology with that region from X.laevis rDNA. We have also demonstrated faithful transcription from this origin using cloned X.borealis rDNA in an extract derived from X. laevis culture cells. This in vitro transcription was insensitive to 100 micrograms/ml alpha-amanatin, suggesting that it was mediated by RNA polymerase 1.
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18
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Jones NC, Richter JD, Weeks DL, Smith LD. Regulation of adenovirus transcription by an E1a gene in microinjected Xenopus laevis oocytes. Mol Cell Biol 1983; 3:2131-42. [PMID: 6318084 PMCID: PMC370083 DOI: 10.1128/mcb.3.12.2131-2142.1983] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The regulation of adenovirus type 5 gene expression by the E1a gene product was examined in microinjected Xenopus laevis oocytes. Chimeric genes were constructed which included the promoter region of early adenovirus type 5 gene 3 and the structural sequence which codes for the bacterial enzyme chloramphenicol-3-O-acetyltransferase (CAT). A plasmid containing this chimeric gene as well as plasmids containing the E1a gene were coinjected into oocyte nuclei. The presence of the E1a gene was shown to increase CAT activity by up to 8.5-fold over basal levels. Synthesis of the functional product from the E1a gene requires the removal of intron sequences by RNA splicing. The E1a gene and a derivative that precisely lacks the intron were equally effective in increasing CAT activity, suggesting that splicing of the primary E1a transcript is efficiently accomplished in the oocyte nucleus. This was confirmed by directly examining the E1a mRNAs by the S1 mapping procedure. A protein extract from adenovirus type 5-infected HeLa cells enriched for the E1a protein may supplant the E1a plasmid in enhancing CAT activity. Synthesis of the CAT enzyme after gene injection is invariant in oocytes from the same frog, but oocytes from different frogs show a high degree of variability in their ability to synthesize the CAT enzyme. Microinjected X. laevis oocytes appear to be an extremely useful system to study the effects of protein elements on transcription.
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19
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Abstract
We have noted previously that when circular, but not linear, DNA or chromatin was injected into Xenopus laevis oocytes, much of it went through an intermediate form in which it did not readily enter an agarose gel; after a few hours, it reappeared as monomer DNA that had acquired its full complement of nucleosomes (T. J. Miller and J. E. Mertz, Mol. Cell. Biol. 2:1581-1593, 1982). We determined, using electron microscopy and a variety of biochemical techniques, the structure of this aggregated material. Most of it was oligomeric and multimeric catenanes of the injected sample. In addition, injection of DNA that had been catenated in vitro with DNA gyrase resulted in the conversion of most of it back to monomer circles. These findings demonstrate directly that both catenation and decatenation of DNA occur in vivo under physiological conditions. Whether these reactions play a crucial role in nucleosome formation, as well as in DNA replication and recombination, remains to be determined.
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20
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Abstract
We have noted previously that when circular, but not linear, DNA or chromatin was injected into Xenopus laevis oocytes, much of it went through an intermediate form in which it did not readily enter an agarose gel; after a few hours, it reappeared as monomer DNA that had acquired its full complement of nucleosomes (T. J. Miller and J. E. Mertz, Mol. Cell. Biol. 2:1581-1593, 1982). We determined, using electron microscopy and a variety of biochemical techniques, the structure of this aggregated material. Most of it was oligomeric and multimeric catenanes of the injected sample. In addition, injection of DNA that had been catenated in vitro with DNA gyrase resulted in the conversion of most of it back to monomer circles. These findings demonstrate directly that both catenation and decatenation of DNA occur in vivo under physiological conditions. Whether these reactions play a crucial role in nucleosome formation, as well as in DNA replication and recombination, remains to be determined.
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Mertz JE, Murphy A, Barkan A. Mutants deleted in the agnogene of simian virus 40 define a new complementation group. J Virol 1983; 45:36-46. [PMID: 6296443 PMCID: PMC256384 DOI: 10.1128/jvi.45.1.36-46.1983] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Analysis of the DNA sequence of the late leader region of simian virus 40 indicates that it might encode a 61-amino acid, highly basic protein, LP-1. Mutants deleted in this region are viable, but they produce infectious progeny more slowly than wild-type virus in established monkey cells. On the basis of the rates of appearance and the sizes of mixed plaques formed after cotransfections with pairs of mutants, we found that mutants defective in the synthesis of LP-1 complementation was also observed in infections with virions and was bidirectional. Therefore, these mutants define a new complementation group, group G. In addition, a protein of the appropriate molecular weight for LP-1 (approximately 8 X 10(3) ) was synthesized by wild-type virus-infected cells but not by mock-infected or group G gene mutant-infected cells. This protein, whose identity has been established definitively by Jay et al. (Nature (London) 291:346-349, 1981), was synthesized at a high rate at late times after infection, was present predominantly in the cytoplasmic fraction of cells, possessed a fairly short half-life, and was absent from mature virions. Once formed, virions of group G gene mutants behaved biologically and physically like virions of wild-type virus. On the basis of these findings and other known properties of LP-1 and mutants defective in LP-1 synthesis, we hypothesize that LP-1 functions to facilitate virion assembly, possibly by serving as a nonreusable scaffolding protein.
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