Herpes Simplex Virus Type 1 Single Strand DNA Binding Protein and Helicase/Primase Complex Disable Cellular ATR Signaling

• DOI: 10.1371/journal.ppat.1003652
• Publication Date: 2013-10-03T21:08:57Z
• Authors: Kareem N. Mohni; Samantha Smith; Alexander R. Dee; April J. Schumacher; Sandra K. Weller
• Keywords: Exonucleases; 0301 basic medicine; QH301-705.5; Cell Cycle Proteins; Ataxia Telangiectasia Mutated Proteins; DNA Primase; Herpesvirus 1, Human; Viral Proteins; 03 medical and health sciences; Chlorocebus aethiops; Animals; Humans; Biology (General); Vero Cells; DNA Helicases; Nuclear Proteins; RC581-607; 3. Good health; DNA-Binding Proteins; DNA, Viral; Immunologic diseases. Allergy; Carrier Proteins; Research Article; HeLa Cells; Signal Transduction

Herpes Simplex Virus type 1 (HSV-1) has evolved to disable the cellular DNA damage response kinase, ATR. We have previously shown that HSV-1-infected cells are unable to phosphorylate the ATR substrate Chk1, even under conditions in which replication forks are stalled. Here we report that the HSV-1 single stranded DNA binding protein (ICP8), and the helicase/primase complex (UL8/UL5/UL52) form a nuclear complex in transfected cells that is necessary and sufficient to disable ATR signaling. This complex localizes to sites of DNA damage and colocalizes with ATR/ATRIP and RPA, but under these conditions, the Rad9-Rad1-Hus1 checkpoint clamp (9-1-1) do not. ATR is generally activated by substrates that contain ssDNA adjacent to dsDNA, and previous work from our laboratory has shown that ICP8 and helicase/primase also recognize this substrate. We suggest that these four viral proteins prevent ATR activation by binding to the DNA substrate and obstructing loading of the 9-1-1 checkpoint clamp. Exclusion of 9-1-1 prevents recruitment of TopBP1, the ATR kinase activator, and thus effectively disables ATR signaling. These data provide the first example of viral DNA replication proteins obscuring access to a DNA substrate that would normally trigger a DNA damage response and checkpoint signaling. This unusual mechanism used by HSV suggests that it may be possible to inhibit ATR signaling by preventing recruitment of the 9-1-1 clamp and TopBP1.