The NS1 protein of the parvovirus MVM Aids in the localization of the viral genome to cellular sites of DNA damage.

Kinjal Majumder,Trupti Joshi,Matthew S Fuller,Juexin Wang,David J Pintel,Maria Boftsi,Fawn B Whittle,Patrick Hearing

doi:10.1371/journal.ppat.1009002

Abstract

The autonomous parvovirus Minute Virus of Mice (MVM) localizes to cellular DNA damage sites to establish and sustain viral replication centers, which can be visualized by focal deposition of the essential MVM non-structural phosphoprotein NS1. How such foci are established remains unknown. Here, we show that NS1 localized to cellular sites of DNA damage independently of its ability to covalently bind the 5’ end of the viral genome, or its consensus DNA binding sequence. Many of these sites were identical to those occupied by virus during infection. However, localization of the MVM genome to DNA damage sites occurred only when wild-type NS1, but not its DNA-binding mutant was expressed. Additionally, wild-type NS1, but not its DNA binding mutant, could localize a heterologous DNA molecule containing the NS1 binding sequence to DNA damage sites. These findings suggest that NS1 may function as a bridging molecule, helping the MVM genome localize to cellular DNA damage sites to facilitate ongoing virus replication.

Highlights

Parvoviruses are non-enveloped icosahedral viruses that contain a linear genome of singlestranded DNA [1]
We have previously shown that the parvovirus Minute Virus of Mice (MVM) establishes replication centers at sites that are associated with cellular regions of DNA damage
When U2OS cells were infected with an MVM mutant unable to generate NS2 (MVMΔNS2), NS1 colocalized with micro-irradiated DNA Damage Response (DDR) sites (Fig 1A, panel 3), suggesting that NS2 was not required for this localization

Summary

Introduction

Parvoviruses are non-enveloped icosahedral viruses that contain a linear genome of singlestranded DNA [1]. The prototype parvovirus Minute Virus of Mice (MVM) is lytic in murine cells and transformed cells of multiple species including human, and replicates autonomously during S phase through rolling hairpin replication [2,3]. The MVM genome is approximately 5 kb long with inverted terminal repeats at either end which serve as replication origins. Following S phase entry, the single-stranded MVM genome is amplified by alternating monomeric and concatemeric duplex replicative intermediates, utilizing cellular DNA polymerase δ. Besides binding to its consensus DNA motif, NS1 facilitates genome replication as a site- and strand-specific nickase and helicase, and covalently binds to the 5’ end of the viral genome during replication [6,11,12,13,14]

Methods

Results

Discussion

Conclusion