Simian Virus 40 Induces Multiple S Phases with the Majority of Viral DNA Replication in the G2 and Second S Phase in CV-1 Cells

Lehman, John M.; Laffin, Judith; Friedrich, Thomas

doi:10.1006/excr.2000.4927

Cited by 25 publications

(23 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Determi- nation of the rate of a Ͼ G 2 DNA content showed that 80% of infected CV-1 cells had DNA contents of Ͼ4N at 64 hpi. Thus, the data confirmed that SV40 lytic infection of permissive cells, such as CV-1, induces the reinitiation of DNA synthesis within a single cell cycle, resulting in the production of polyploid cells (28). Moreover, infected TO-CV-1-shRNAp21 cells, in which Dox-induced expression of shRNAp21 knocks down endogenous p21 at the RNA level (Fig.…”

Section: Resultssupporting

confidence: 71%

Simian Virus 40 Activates ATR-Δp53 Signaling To Override Cell Cycle and DNA Replication Control

Rohaly

Korf

Dehde

et al. 2010

J Virol

View full text Add to dashboard Cite

During infection, simian virus 40 (SV40) attempts to take hold of the cell, while the host responds with various defense systems, including the ataxia-telangiectasia mutated/ATM-Rad3 related (ATM/ATR)-mediated DNA damage response pathways. Here we show that upon viral infection, ATR directly activates the p53 isoform ⌬p53, leading to upregulation of the Cdk inhibitor p21 and downregulation of cyclin A-Cdk2/1 (AK) activity, which force the host to stay in the replicative S phase. Moreover, downregulation of AK activity is a prerequisite for the generation of hypophosphorylated, origin-competent DNA polymerase ␣-primase (hypoPol␣), which is, unlike AK-phosphorylated Pol␣ (P-Pol␣), recruited by SV40 large T antigen (T-Ag) to initiate viral DNA replication. Prevention of the downregulation of AK activity by inactivation of ATR-⌬p53-p21 signaling significantly reduced the T-Ag-interacting hypo-Pol␣ population and, accordingly, SV40 replication efficiency. Moreover, the ATR-⌬p53 pathway facilitates the proteasomal degradation of the 180-kDa catalytic subunit of the non-T-Ag-interacting P-Pol␣, giving rise to T-Ag-interacting hypo-Pol␣. Thus, the purpose of activating the ATR-⌬p53-p21-mediated intra-S checkpoint is to maintain the host in S phase, an optimal environment for SV40 replication, and to modulate the host DNA replicase, which is indispensable for viral amplification.Infection of quiescent CV-1 cells with the primate polyomavirus simian virus 40 (SV40) induces cell cycle progression and stimulates host cell DNA replication, which is mandatory for viral amplification. SV40 uses only a single viral protein, T antigen (T-Ag), for its own replication; all other components have to be provided by the host. Initially, a specifically phosphorylated subclass of T-Ag binds to a palindromic sequence in the SV40 origin (43), and in the presence of ATP, T-Ag forms a double-hexamer nucleoprotein complex leading to structural distortion and unwinding of origin DNA sequences (5). In concert with the cellular single-strand DNA binding protein RPA and topoisomerase I, the DNA helicase activity of T-Ag promotes more-extensive origin unwinding, forming a preinitiation complex (pre-RC), resulting in an initiation complex (53). Once the initiation complex forms, the primase activity of the heterotetrameric DNA polymerase ␣-primase (Pol␣) complex, consisting of the p180 catalytic subunit, the p70 regulatory subunit, and the p48/58 primase subunits, synthesizes a short RNA primer on each template strand, which is extended by the DNA polymerase activity of Pol␣ (6, 17). Immediately after the first nascent RNA/DNA primer is synthesized, the complete replication machinery is assembled, and elongation at both forks by the processive DNA polymerase ␦ ensues (62). Thus, during the initiation of SV40 replication, T-Ag performs many of the functions attributed to the eukaryotic pre-RC complex proteins, including Orc, Cdc6, Cdt1, and kinase-independent cyclin E, which facilitates loading of the putative replication helicase Mcm2-7 onto the e...

show abstract

Section: Resultssupporting

confidence: 71%

Simian Virus 40 Activates ATR-Δp53 Signaling To Override Cell Cycle and DNA Replication Control

Rohaly

Korf

Dehde

et al. 2010

J Virol

View full text Add to dashboard Cite

show abstract

“…These results suggest that JCV DNA is replicated in G 2 -arrested cells, with the recovery from such arrest occurring as the abundance of TAg declines. In contrast to SV40 (43), infection with JCV does not appear to induce abnormal replication of cellular DNA resulting in a DNA content of Ͼ4 N. The replication of JCV DNA is thus accomplished during G 2 arrest without a second round of cellular DNA synthesis.…”

Section: Discussionmentioning

confidence: 87%

Large T Antigen Promotes JC Virus Replication in G2-arrested Cells by Inducing ATM- and ATR-mediated G2 Checkpoint Signaling

Orba

Suzuki

Makino

et al. 2010

Journal of Biological Chemistry

View full text Add to dashboard Cite

The human polyomavirus JC virus (JCV) 2 is the causative agent of progressive multifocal leukoencephalopathy (PML), a fatal demyelinating disease of the central nervous system. JCV infection usually occurs during childhood, but remains subclinical. However, opportunistic reactivation of JCV results in the development of PML in individuals with a compromised immune system, such as those with acquired immunodeficiency syndrome (AIDS) or advanced-stage malignant tumors, or those recently having undergone organ transplantation with immunosuppressive therapy (1). There is currently no effective or specific therapy for PML, even though the incidence of this condition is increasing with the growing number of individuals with AIDS.JCV is a small virus with a double-stranded DNA genome that encodes early proteins (large T antigen, small t antigen, and TЈ antigen) and late proteins (VP1, VP2, VP3, and agnoprotein) (2). The entry of JCV into the nucleus of an infected cell is followed by transcription of the early genes and the production of large T antigen (TAg). The replication of JCV DNA progresses in association with the accumulation of TAg, which subsequently stimulates transcription of late genes and represses that of the early genes (3). JCV TAg shares 72% amino acid sequence identity with TAg of simian virus 40 (SV40), another primate polyomavirus, and, like SV40 TAg, it is necessary for replication of the viral genome as a result of its DNA binding and helicase activities. The replication of polyomaviruses also requires DNA replication proteins of the host cell, such as DNA polymerase ␣, topoisomerases, and replication protein A (RPA) (4, 5), with such host cell factors being thought to serve as determinants of host specificity (6).The utilization of such cellular proteins requires that polyomaviruses replicate in a phase of the cell cycle in which they are available. Polyomavirus TAg thus modulates cellular signaling pathways to induce quiescent cells to enter S phase, in which cellular DNA is replicated (7). A key event in this process is the interaction of TAg with members of the retinoblastoma protein family, which results in inactivation of retinoblastoma protein and in consequent progression of the cell cycle (8). Moreover, polyomaviruses are thought to take advantage of the DNA damage response to enhance viral replication. SV40 lytic infection thus triggers the DNA damage checkpoint, resulting in a bypass of mitosis and additional replication of cellular and viral DNA (9), and murine polyomavirus-infected cells accumulate in S and G 2 phases (10). Replication of viral DNA in cells *

show abstract

“…This synthesis, however, may occur out of normal cell cycle control, and it does not involve a full round of the cell cycle since mitosis does not follow the S phase (197,198). However, in vivo studies in our laboratory have provided no evidence for DNA synthesis following Py infection in vivo (233).…”

Section: Dna Synthesismentioning

confidence: 87%

Natural Biology of Polyomavirus Middle T Antigen

Gottlieb

Villarreal

2001

Microbiol Mol Biol Rev

View full text Add to dashboard Cite

“It has been commented by someone that ‘polyoma’ is an adjective composed of a prefix and suffix, with no root between—a meatless linguistic sandwich” (C. J. Dawe). The very name “polyomavirus” is a vague mantel: a name given before our understanding of these viral agents was clear but implying a clear tumor life-style, as noted by the late C. J. Dawe. However, polyomavirus are not by nature tumor-inducing agents. Since it is the purpose of this review to consider the natural function of middle T antigen (MT), encoded by one of the seemingly crucial transforming genes of polyomavirus, we will reconsider and redefine the virus and its MT gene in the context of its natural biology and function. This review was motivated by our recent in vivo analysis of MT function. Using intranasal inoculation of adult SCID mice, we have shown that polyomavirus can replicate with an MT lacking all functions associated with transformation to similar levels to wild-type virus. These observations, along with an almost indistinguishable replication of all MT mutants with respect to wild-type viruses in adult competent mice, illustrate that MT can have a play subtle role in acute replication and persistence. The most notable effect of MT mutants was in infections of newborns, indicating that polyomavirus may be highly adapted to replication in newborn lungs. It is from this context that our current understanding of this well-studied virus and gene is presented

show abstract

Simian Virus 40 Induces Multiple S Phases with the Majority of Viral DNA Replication in the G2 and Second S Phase in CV-1 Cells

Cited by 25 publications

References 28 publications

Simian Virus 40 Activates ATR-Δp53 Signaling To Override Cell Cycle and DNA Replication Control

Simian Virus 40 Activates ATR-Δp53 Signaling To Override Cell Cycle and DNA Replication Control

Large T Antigen Promotes JC Virus Replication in G2-arrested Cells by Inducing ATM- and ATR-mediated G2 Checkpoint Signaling

Natural Biology of Polyomavirus Middle T Antigen

Contact Info

Product

Resources

About