Roles of ATM and ATR-Mediated DNA Damage Responses during Lytic BK Polyomavirus Infection

Mengxi Jiang,Linbo Zhao,Monica Gamez,Michael J Imperiale,James Pipas

doi:10.1371/journal.ppat.1002898

Abstract

BK polyomavirus (BKPyV) is an emerging pathogen whose reactivation causes severe disease in transplant patients. Unfortunately, there is no specific anti-BKPyV treatment available, and host cell components that affect the infection outcome are not well characterized. In this report, we examined the relationship between BKPyV productive infection and the activation of the cellular DNA damage response (DDR) in natural host cells. Our results showed that both the ataxia-telangiectasia mutated (ATM)- and ATM and Rad-3-related (ATR)-mediated DDR were activated during BKPyV infection, accompanied by the accumulation of polyploid cells. We assessed the involvement of ATM and ATR during infection using small interfering RNA (siRNA) knockdowns. ATM knockdown did not significantly affect viral gene expression, but reduced BKPyV DNA replication and infectious progeny production. ATR knockdown had a slightly more dramatic effect on viral T antigen (TAg) and its modified forms, DNA replication, and progeny production. ATM and ATR double knockdown had an additive effect on DNA replication and resulted in a severe reduction in viral titer. While ATM mainly led to the activation of pChk2 and ATR was primarily responsible for the activation of pChk1, knockdown of all three major phosphatidylinositol 3-kinase-like kinases (ATM, ATR, and DNA-PKcs) did not abolish the activation of γH2AX during BKPyV infection. Finally, in the absence of ATM or ATR, BKPyV infection caused severe DNA damage and aberrant TAg staining patterns. These results indicate that induction of the DDR by BKPyV is critical for productive infection, and that one of the functions of the DDR is to minimize the DNA damage which is generated during BKPyV infection.

Highlights

BK polyomavirus (BKPyV) was first isolated in 1971 from a renal transplant patient [1] and has gained much interest in the past two decades due to its disease prevalence in immunocompromised patients [2]
We are interested in understanding the interactions between BKPyV and host cell components or pathways, with the aim of developing more BKPyV-specific antiviral treatment options
In this study we characterized the relationship between BKPyV infection and the cellular DNA damage response (DDR), a signaling cascade that is initiated by cells to repair damaged DNA molecules

Summary

Introduction

BK polyomavirus (BKPyV) was first isolated in 1971 from a renal transplant patient [1] and has gained much interest in the past two decades due to its disease prevalence in immunocompromised patients [2]. Especially in renal transplant and bone marrow transplant recipients, the virus can reactivate from a persistent state to lytic infection, which results in severe disease including polyomavirus-associated nephropathy (PVAN) and hemorrhagic cystitis (HC), respectively [2]. The common approach to control BKPyV reactivation is palliative care for HC patients, or combining immunosuppression reduction with drugs that inhibit viral DNA replication for PVAN, there are often conflicting outcomes with these treatment options [3]. TAg sets up the host environment for viral DNA replication by inducing cells into S phase and, at the same time, inhibiting the p53-dependent apoptotic pathway [4]. Replicated viral DNA is encapsidated by the capsid proteins VP1, VP2, and VP3, and this is followed by viral egress and cell lysis, completing the life cycle. Identification and characterization of these interactions is extremely important, since it may reveal novel anti-viral therapeutic targets

Methods

Results

Discussion

Conclusion