Bi-directional routing of DNA mismatch repair protein human exonuclease 1 to replication foci and DNA double strand breaks.

Human exonuclease 1 (hEXO1) is implicated in DNA metabolism, including replication, recombination and repair, substantiated by its interactions with PCNA, DNA helicases BLM and WRN, and several DNA mismatch repair (MMR) proteins. We investigated the sub-nuclear localization of hEXO1 during S-phase progression and in response to laser-induced DNA double strand ...
breaks (DSBs). We show that hEXO1 and PCNA co-localize in replication foci. This apparent interaction is sustained throughout S-phase. We also demonstrate that hEXO1 is rapidly recruited to DNA DSBs. We have identified a PCNA interacting protein (PIP-box) region on hEXO1 located in its COOH-terminal ((788)QIKLNELW(795)). This motif is essential for PCNA binding and co-localization during S-phase. Recruitment of hEXO1 to DNA DSB sites is dependent on the MMR protein hMLH1. We show that two distinct hMLH1 interaction regions of hEXO1 (residues 390-490 and 787-846) are required to direct the protein to the DNA damage site. Our results reveal that protein domains in hEXO1 in conjunction with specific protein interactions control bi-directional routing of hEXO1 between on-going DNA replication and repair processes in living cells.
Mesh Terms:
Adaptor Proteins, Signal Transducing, Amino Acid Motifs, Amino Acid Substitution, Animals, DNA, DNA Breaks, Double-Stranded, DNA Mismatch Repair, DNA Repair Enzymes, DNA Replication, DNA-Binding Proteins, Exodeoxyribonucleases, HeLa Cells, Humans, Lasers, Mice, MutL Protein Homolog 1, MutS Homolog 3 Protein, NIH 3T3 Cells, Nuclear Proteins, Proliferating Cell Nuclear Antigen, Protein Transport, RecQ Helicases, Recombinant Fusion Proteins, S Phase, Werner Syndrome Helicase
DNA Repair (Amst)
Date: Jan. 02, 2011
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