Identification of Base Excision Repair Activities Associated With the Herpes Simplex Virus Type‐1 Replisome

Abstract

We are interested in studying events at the HSV‐1 replication fork, processes that are dependent on six core viral gene products: the heterodimeric DNA polymerase‐clamp assembly (UL30/UL42), the DNA helicase‐primase (UL5/UL8/UL52) and the single‐strand DNA binding protein (ICP8/UL29). In an effort to identify additional factors that are active at the viral DNA replication fork, we searched for polymerase interacting proteins. We identified the viral uracil DNA glycosylase (UL2) as a protein that co‐purifies with the polymerase through numerous chromatographic steps, an interaction that was verified by co‐immunoprecipitation. We found that the interaction with UL2 is mediated through the UL30 subunit. Moreover, UL2 co‐localizes with UL30 to nuclear viral replication compartments. In addition, we have observed that UL30 specifically cleaves abasic DNA in a manner independent of divalent cation, resembling the activity of a lyase. This property would make the HSV‐1 DNA polymerase functionally analogous to the mitochondrial DNA polymerase gamma in as much as it possesses DNA synthesis, proofreading and lyase activities. These findings raise the interesting notion that the viral replisome promotes replication‐coupled base excision repair.