title: XRCC1 co-localizes and physically interacts with PCNA.
abstract: X-ray Repair Cross Complementing 1 (XRCC1) is thought to function as a scaffolding protein in both base excision repair and single-strand break repair (SSBR), since it interacts with several proteins participating in these related pathways and has no known enzymatic activity. Moreover, studies indicate that XRCC1 possesses discrete G1 and S phase-specific functions. To further define the contribution of XRCC1 to DNA metabolism, we determined the in vivo localization pattern of this protein and searched for novel protein interactors. We report here that XRCC1 co-localizes with proliferating cell nuclear antigen (PCNA) at DNA replication foci, observed exclusively in the S phase of undamaged HeLa cells. Furthermore, fluorescence resonance energy transfer (FRET) analysis and co-immunoprecipitation indicate that XRCC1 and PCNA are in a complex and likely physically interact in vivo. In vitro biochemical analysis demonstrated that these two proteins associate directly, with the interaction being mediated by residues between amino acids 166 and 310 of XRCC1. The current evidence suggests a model where XRCC1 is sequestered via its interaction with PCNA to sites of DNA replication factories to facilitate efficient SSBR in S phase.
authors.affiliation: Laboratory of Molecular Gerontology, National Institute on Aging, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA.
authors.forename: Jinshui
authors.initials: J
authors.lastname: Fan
authors.forename: Marit
authors.initials: M
authors.lastname: Otterlei
authors.forename: Heng-Kuan
authors.initials: HK
authors.lastname: Wong
authors.forename: Alan E
authors.initials: AE
authors.lastname: Tomkinson
authors.forename: David M
authors.initials: DM
authors.lastname: Wilson
mesh_terms: D002457:Cell Extracts; D002467:Cell Nucleus / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D006367:HeLa Cells; D006801:Humans; D011233:Precipitin Tests; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D016196:S Phase; D000076105:X-ray Repair Cross Complementing Protein 1
chemical_list: D002457:Cell Extracts; D004268:DNA-Binding Proteins; D018809:Proliferating Cell Nuclear Antigen; D000076105:X-ray Repair Cross Complementing Protein 1; C000619371:XRCC1 protein, human