The HSV-1 Exonuclease, UL12, Stimulates Recombination by a Single Strand Annealing Mechanism

PLoS Pathogens

Eric A. Hendrickson¹  Yinan Kan¹  Jeremy M. Stark²  Kareem N. Mohni³  Sandra K. Weller³  April J. Schumacher³ 

[1] Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America;Department of Cancer Biology, Beckman Research Institute of the City of Hope, Duarte, California, United States of America;Molecular, Microbial and Structural Biology Department, University of Connecticut Health Center, Farmington, Connecticut, United States of America

关键词: DNA replication;    DNA recombination;    Single-str;    annealing;    Plasmid construction;    Recombinant proteins;    DNA repair;    Non-homologous end joining;    Viral replication;   

DOI  :  10.1371/journal.ppat.1002862

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Production of concatemeric DNA is an essential step during HSV infection, as the packaging machinery must recognize longer-than-unit-length concatemers; however, the mechanism by which they are formed is poorly understood. Although it has been proposed that the viral genome circularizes and rolling circle replication leads to the formation of concatemers, several lines of evidence suggest that HSV DNA replication involves recombination-dependent replication reminiscent of bacteriophages λ and T4. Similar to λ, HSV-1 encodes a 5′-to-3′ exonuclease (UL12) and a single strand annealing protein [SSAP (ICP8)] that interact with each other and can perform strand exchange in vitro. By analogy with λ phage, HSV may utilize viral and/or cellular recombination proteins during DNA replication. At least four double strand break repair pathways are present in eukaryotic cells, and HSV-1 is known to manipulate several components of these pathways. Chromosomally integrated reporter assays were used to measure the repair of double strand breaks in HSV-infected cells. Single strand annealing (SSA) was increased in HSV-infected cells, while homologous recombination (HR), non-homologous end joining (NHEJ) and alternative non-homologous end joining (A-NHEJ) were decreased. The increase in SSA was abolished when cells were infected with a viral mutant lacking UL12. Moreover, expression of UL12 alone caused an increase in SSA, which was completely eliminated when a UL12 mutant lacking exonuclease activity was expressed. UL12-mediated stimulation of SSA was decreased in cells lacking the cellular SSAP, Rad52, and could be restored by coexpressing the viral SSAP, ICP8, indicating that an SSAP is also required. These results demonstrate that UL12 can specifically stimulate SSA and that either ICP8 or Rad52 can function as an SSAP. We suggest that SSA is the homology-mediated repair pathway utilized during HSV infection.

【 授权许可】

CC BY