A role for MRE11, NBS1, and recombination junctions in replication and stable maintenance of EBV episomes.
Recombination-like structures formed at origins of DNA replication may contribute to replication fidelity, sister chromatid cohesion, chromosome segregation, and overall genome stability. The Epstein-Barr Virus (EBV) origin of plasmid replication (OriP) provides episomal genome stability through a poorly understood mechanism. We show here that recombinational repair proteins MRE11 and NBS1 are recruited to the Dyad Symmetry (DS) region of OriP in a TRF2- and cell cycle-dependent manner. Depletion of MRE11 or NBS1 by siRNA inhibits OriP replication and destabilized viral episomes. OriP plasmid maintenance was defective in MRE11 and NBS1 hypomorphic fibroblast cell lines and only integrated, non-episomal forms of EBV were detected in a lympoblastoid cell line derived from an NBS1-mutated individual. Two-dimensional agarose gel analysis of OriP DNA revealed that recombination-like structures resembling Holliday-junctions form at OriP in mid S phase. MRE11 and NBS1 association with DS coincided with replication fork pausing and origin activation, which preceded the formation of recombination structures. We propose that NBS1 and MRE11 promote replication-associated recombination junctions essential for EBV episomal maintenance and genome stability.
The Wistar Institute, Philadelphia, Pennsylvania, United States of America.
Jayaraju
J
Dheekollu
Zhong
Z
Deng
Andreas
A
Wiedmer
Matthew D
MD
Weitzman
Paul M
PM
Lieberman
D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004587:Electrophoresis, Agar Gel; D004854:Herpesvirus 4, Human / Q000502:physiology*; D006801:Humans; D000076228:MRE11 Homologue Protein; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D010957:Plasmids; D034741:RNA, Small Interfering; D011995:Recombination, Genetic; D014779:Virus Replication / Q000502:physiology*
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C121766:MRE11 protein, human; C112156:NBN protein, human; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D000076228:MRE11 Homologue Protein