Article

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

Department of Molecular Pathobiology, Research Center for Zoonosis Control, Hokkaido University, N20, W10, Kita-ku, Sapporo 001-0020, Japan.
Journal of Biological Chemistry (Impact Factor: 4.57). 11/2009; 285(2):1544-54. DOI: 10.1074/jbc.M109.064311
Source: PubMed

ABSTRACT Large T antigen (TAg) of the human polyomavirus JC virus (JCV) possesses DNA binding and helicase activities, which, together with various cellular proteins, are required for replication of the viral genome. We now show that JCV-infected cells expressing TAg accumulate in the G(2) phase of the cell cycle as a result of the activation of ATM- and ATR-mediated G(2) checkpoint pathways. Transient transfection of cells with a TAg expression vector also induced G(2) checkpoint signaling and G(2) arrest. Analysis of TAg mutants with different subnuclear localizations suggested that the association of TAg with cellular DNA contributes to the induction of G(2) arrest. Abrogation of G(2) arrest by inhibition of ATM and ATR, Chk1, and Wee1 suppressed JCV genome replication. In addition, abrogation of the G(2)-M transition by Cdc2 depletion disabled Wee1 depletion-induced suppression of JCV genome replication, suggesting that JCV replication is facilitated by G(2) arrest resulting from G(2) checkpoint signaling. Moreover, inhibition of ATM and ATR by caffeine suppressed JCV production. The observation that oligodendrocytes productively infected with JCV in vivo also undergo G(2) arrest suggests that G(2) checkpoint inhibitors such as caffeine are potential therapeutic agents for JCV infection.

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    • "Inspection of Fig. 3C (top line) provides additional evidence that in C33A cells, JCV T-ag is in the nuclei where it clusters in discrete foci. An analogous punctate distribution of T-ag in the nuclei of replication competent cells was seen in previous studies of SV40 DNA Zhao et al., 2008 and JCV replication ((Gasparovic et al., 2009; Orba et al., 2010; Shishido-Hara et al., 2008); reviewed in (Shishido-Hara, 2010)). Inspection of Fig. 3C (middle and bottom rows) establishes that a similar punctate distribution of JCV T-ag occurs in the Hs 683 and U87 cells. "
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    • "Interaction with p53 also prevents apoptosis induced by checkpoint activation when cells aberrantly enter S phase [10]. Additionally, large T antigen can promote viral replication in G2-arrested cells by inducing DNA damage response pathways, and this function was related to binding of cellular DNA by TAg [9]. "
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    • "In addition to their influence upon the G1/S phase transition of the cell cycle, polyomaviruses promote cell cycle arrest at the G2/M phase (Davy and Doorbar, 2007). JCV TAg induces G2 arrest as a result of the activation of the ATM and ATR checkpoint pathways, thereby promoting viral replication in permissive cells (Orba et al. 2010). βTrCP1 is a key player in the S and G2 DNA damage checkpoint pathways, and it promotes cell cycle arrest following DNA damage by attenuating CDK1 activity through degradation of Cdc25A. "
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