title: Mechanism of proliferating cell nuclear antigen clamp opening by replication factor C.
abstract: The eukaryotic replication factor C (RFC) clamp loader is an AAA+ spiral-shaped heteropentamer that opens and closes the circular proliferating cell nuclear antigen (PCNA) clamp processivity factor on DNA. In this study, we examined the roles of individual RFC subunits in opening the PCNA clamp. Interestingly, Rfc1, which occupies the position analogous to the delta clamp-opening subunit in the Escherichia coli clamp loader, is not required to open PCNA. The Rfc5 subunit is required to open PCNA. Consistent with this result, Rfc2.3.4.5 and Rfc2.5 subassemblies are capable of opening and unloading PCNA from circular DNA. Rfc5 is positioned opposite the PCNA interface from Rfc1, and therefore, its action with Rfc2 in opening PCNA indicates that PCNA is opened from the opposite side of the interface that the E. coli delta wrench acts upon. This marks a significant departure in the mechanism of eukaryotic and prokaryotic clamp loaders. Interestingly, the Rad.RFC DNA damage checkpoint clamp loader unloads PCNA clamps from DNA. We propose that Rad.RFC may clear PCNA from DNA to facilitate shutdown of replication in the face of DNA damage.
authors.affiliation: Rockefeller University, New York, New York 10021.
authors.forename: Nina Y
authors.initials: NY
authors.lastname: Yao
authors.affiliation: Rockefeller University, New York, New York 10021.
authors.forename: Aaron
authors.initials: A
authors.lastname: Johnson
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720.
authors.forename: Greg D
authors.initials: GD
authors.lastname: Bowman
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720; Howard Hughes Medical Institute, New York, New York 10021; Departments of Molecular and Cell Biology and Chemistry, Howard Hughes Medical Institute, University of California, Berkeley, California 94720.
authors.forename: John
authors.initials: J
authors.lastname: Kuriyan
authors.affiliation: Rockefeller University, New York, New York 10021; Howard Hughes Medical Institute, New York, New York 10021. Electronic address: odonnel@mail.rockefeller.edu.
authors.forename: Mike
authors.initials: M
authors.lastname: O'Donnell
mesh_terms: D002850:Chromatography, Gel; D003001:Cloning, Molecular; D004247:DNA / Q000737:chemistry; D004249:DNA Damage; D004260:DNA Repair; D004926:Escherichia coli / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D018809:Proliferating Cell Nuclear Antigen / Q000737:chemistry*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D051818:Replication Protein C / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D020349:Surface Plasmon Resonance
chemical_list: D018809:Proliferating Cell Nuclear Antigen; D004247:DNA; D051818:Replication Protein C