Replication of SV40 and Polyoma Virus Chromosomes

DePamphilis, Melvin L.; Bradley, Margaret K.

doi:10.1007/978-1-4613-2221-4_3

Cited by 136 publications

(84 citation statements)

References 721 publications

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“…It is known that most intracellular T antigen is located in the nucleus where it is involved in the regulation of gene activity and in DNA replication (reviewed by DePamphilis and Bradley, 1986), and our finding that T antigen is able to separate the complementary strands in DNA . RNA hybrids suggests a previously unsuspected role in transcriptional regulation.…”

Section: Discussionsupporting

confidence: 58%

Simian‐virus‐40 large‐T‐antigen‐catalyzed DNA and RNA unwinding reactions

Scheffner

Knippers

Stahl

1991

European Journal of Biochemistry

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Simian virus 40 large T antigen is a helicase separating the complementary strands of double-stranded DNA in the presence of hydrolyzable ATP and of double-stranded RNA in the presence of non-ATP nucleotides (GTP, CTP or UTP). We have constructed partially single-stranded nucleic acid substrates consisting of RNA or DNA strands hydrogen bonded to either RNA or DNA complements. We found that ATP is utilized as a cofactor for the T-antigen-catalyzed unwinding reaction when the substrates contain overhanging single-stranded DNA, regardless of whether the double-stranded region is DNA or hybrid DNA . RNA. Conversely, non-ATP nucleotides are used when the overhanging single strand is RNA. Based on these and additional findings, we propose that the bound nucleic acid induces a conformational change in T antigen resulting in a proper orientation of both nucleic acid and nucleotide relative to the active center of the ATPase/helicase domain of the enzyme. The implications of our conclusion for the roles which T antigen may play in vivo are discussed.Large T antigen, the regulatory protein of simian virus 40 (SV40), combines on one polypeptide chain several different functions including that of a helicase which, remarkably, separates not only the hydrogen bonds between complementary strands in double-stranded DNA (Stahl et al., 1986;Wiekowski et al., 1988;Goetz et al., 1988) but also in doublestranded (ds) RNA (Scheffner et al., 1989a). During DNA unwinding, as well as during RNA unwinding, the enzyme proceeds in the 3' to 5' direction of the strand to which it is bound and requires the energy generated by the hydrolysis of nucleoside triphosphates. In spite of these overall similarities there are nevertheless interesting differences between the two nucleic-acid-unwinding reactions.Under in vitro assay conditions T antigen binds to and initiates the unwinding of fully ds DNA of any sequence (Goetz et al., 1988;Scheffner et al., 1989b;Yang et al., 1989). However, the ds segment must be larger than about 60 base pairs to serve as a substrate for the T-antigen-associated DNA helicase activity. Shorter DNA duplices can be unwound by T antigen when they possess 3' single-stranded (ss) extensions Stahl et al., 1988). T antigen binds tightly to its entry site, the junction between ds and ss DNA in partially ds DNA helicase substrates .In contrast, T antigen is unable to initiate the unwinding of completely ds RNA. Rather the enzyme always needs a 3' ss extension of a partially ds RNA substrate as an entry site (Scheffner et al., 1989a). Furthermore, T antigen can unwind many thousand base pairs of ds DNA but fails to unwind ds RNA stretches longer than about 60 bp (Scheffner et al., 1989a).An additional difference between the T-antigen-catalyzed unwinding reactions is that the DNA helicase activity prefer- entially requires the hydrolysis of ATP (or dATP) whereas the in vitro RNA helicase activity depends on a non-ATP nucleotide (UTP, GTP, CTP or the corresponding deoxynucleotide analog) as a cofactor (Scheffner et al., 1989a)....

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Section: Discussionsupporting

confidence: 58%

Simian‐virus‐40 large‐T‐antigen‐catalyzed DNA and RNA unwinding reactions

Scheffner

Knippers

Stahl

1991

European Journal of Biochemistry

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“…The core ori regions of the human (BKV and JCV), monkey (SV40), and murine (Py) papovaviruses are markedly similar (see reference 16 copies during the time interval that host DNA has replicated only once. The organization of the regulatory regions of the two best studied of these viruses, SV40 and Py, is summarized in Fig.…”

Section: Discussionmentioning

confidence: 99%

DNA sequence requirements for replication of polyomavirus DNA in vivo and in vitro.

Prives¹,

Murakami²,

Kern³

et al. 1987

Mol. Cell. Biol.

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Cell extracts of FM3A mouse cells replicate polyomavirus (Py) DNA in the presence of immunoaffinitypurified Py large T antigen, deoxynucleoside triphosphates, ATP, and an ATP-generating system. This system was used to examine the effects of mutations within or adjacent to the Py core origin (on) region in vitro. The analysis of plasmid DNAs containing deletions within the early-gene side of the Py core ori indicated that sequences between nucleotides 41 and 57 define the early boundary of Py DNA replication in vitro. This is consistent with previously published studies on the early-region sequence requirements for Py replication in vivo. Deleting portions of the T-antigen high-affinity binding sites A and B (between nucleotides 57 and 146) on the early-gene side of the core on led to increased levels of replication in vitro and to normal levels of replication in vivo. Point mutations within the core ori region that abolish Py DNA replication in vivo also reduced replication in vitro. A mutant with a reversed orientation of the Py core on region replicated in vitro, but to a lesser extent than wild-type Py DNA. Plasmids with deletions on the late-gene side of the core on, within the enhancer region, that either greatly reduced or virtually abolished Py DNA replication in vivo replicated to levels similar to those of wild-type Py DNA plasmids in vitro. Thus, as has been observed with simian virus 40, DNA sequences needed for Py replication in vivo are different from and more stringent than those required in vitro.Replication of polyomavirus (Py) DNA proceeds bidirectionally from a fixed point within the noncoding region of the viral genome (for a review, see reference 16 and references therein). This replication origin (ori) region (Fig. 1) contains multiple T-antigen (T Ag)-binding sites within a G+C-rich 32-base-pair (bp) sequence of dyad symmetry adjacent to a region in which 13 of 14 residues form A * T pairs. It thus bears structural features similar to the replication ori of simian virus 40 (SV40). However, the relationship of the Py ori to other regulatory signals in the noncoding segment is somewhat different from that of SV40. The number and arrangement of large T Ag high-affinity binding sites on the early side of both viral ori regions differ. Also, the relative affinities of Py and SV40 T Ags for binding sites within their respective ori regions are apparently dissimilar (12,14,28,47). Moreover, while both viruses encode enhancer elements, the Py enhancer is almost directly adjacent to the late boundary of the ori region and consists of a series of discrete elements that bear homologies to other enhancer elements including those of SV40, adenovirus Ela, and mouse immunoglobulin genes (2,22,23,26,31,38,46,51,53). By contrast, the SV40 enhancer, a 72-bp repeated sequence (see reference 22 and references therein), is separated from the core ori by a series of G+C-rich sequences (the 21-bp repeats) that form a distinct transcriptional control element to which the cellular transcription factor, Spl, binds (...

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“…Fill), or a 54-bp tandem duplication of this region (open box, FlOl). The nucleotide numbering system is explained in DePamphilis and Bradley (1986).…”

Section: Gene Expression In Individual Mouse Oocytes and Embryos Is Pmentioning

confidence: 99%

The need for enhancers in gene expression first appears during mouse development with formation of the zygotic nucleus.

Martínez‐Salas

Linney²,

Hassell³

et al. 1989

Genes Dev.

111

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Microinjection of the firefly luciferase gene coupled to a thymidine kinase (tk) promoter provided a quantitative assay to evaluate the requirements for gene expression in individual mouse oocytes and embryos. Polyoma virus (PyV) enhancers had no effect on the level of gene expression or competition for transcription factors as long as the DNA remained either in the oocyte germinal vesicle or the pronuclei of one-cell embryos. Expression of injected genes could be observed in pronuclei because the signal that normally triggers zygotic gene expression in two-cell embryos still occurred in one-cell embryos arrested in S phase. However, when the tk promoter was injected into zygotic nuclei of two-cell embryos, enhancers increased the number of embryos that expressed luciferase as well as the level of luciferase activity per embryo. PyV enhancer mutation FlOl, selected for growth in mouse embryonal carcinoma F9 cells, stimulated expression in developing two-cell embryos about seven times better than the wild-type PyV enhancer and competed effectively for factors required for transcription. These results were consistent with the fact that enhancers are required to activate the PyV origin of DNA replication in developing two-cell embryos but not in one-cell embryos. The maximum levels of gene expression in oocytes, one-cell embryos, and developing two-cell embryos (1 : 67 : 21) were inversely related to the extent of chromatin assembly, but the need for enhancers was independent of chromatin assembly. Therefore, it appears that the need for enhancers to activate promoters or origins of replication results from some negative regulatory factor that first appears as a component of zygotic nuclear structure.

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Replication of SV40 and Polyoma Virus Chromosomes

Cited by 136 publications

References 721 publications

Simian‐virus‐40 large‐T‐antigen‐catalyzed DNA and RNA unwinding reactions

Simian‐virus‐40 large‐T‐antigen‐catalyzed DNA and RNA unwinding reactions

DNA sequence requirements for replication of polyomavirus DNA in vivo and in vitro.

The need for enhancers in gene expression first appears during mouse development with formation of the zygotic nucleus.

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