title: Mechanism of inhibition of proliferating cell nuclear antigen-dependent DNA synthesis by the cyclin-dependent kinase inhibitor p21.
abstract: It is known that the direct binding of the cyclin-dependent kinase (Cdk) inhibitor p21, also called Cdk-interacting protein 1 (p21), to proliferating cell nuclear antigen (PCNA) results in the inhibition of PCNA-dependent DNA synthesis. We provide evidence that p21 first inhibits the replication factor C-catalyzed loading of PCNA onto DNA and second prevents the binding of DNA polymerase delta core to the PCNA clamp assembled on DNA. The second effect contributes most to the inhibition of pol delta holoenzyme activity. p21 primarily inhibited the DNA synthesis resulting from multiple reassembly of DNA polymerase delta holoenzyme. On the other hand, an ability of the PCNA clamp to translocate along double-stranded DNA was not affected by p21. These data were confirmed with a mutant of p21 that is unable to bind PCNA and therefore neither inhibited clamp assembly nor prevented the loading of DNA polymerase delta core onto DNA. Our data suggest that p21 does not discriminate in vitro "repair" and "replication" DNA synthesis based on template length but does act preferentially on polymerization which encounters obstacles to progress.
authors.affiliation: Department of Veterinary Biochemistry, University Zürich-Irchel, Switzerland.
authors.forename: V N
authors.initials: VN
authors.lastname: Podust
authors.forename: L M
authors.initials: LM
authors.lastname: Podust
authors.forename: F
authors.initials: F
authors.lastname: Goubin
authors.forename: B
authors.initials: B
authors.lastname: Ducommun
authors.forename: U
authors.initials: U
authors.lastname: Hübscher
mesh_terms: D001667:Binding, Competitive; D002384:Catalysis; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000494:pharmacology*; D004258:DNA Polymerase III; D004261:DNA Replication / Q000187:drug effects*; D004270:DNA, Circular / Q000096:biosynthesis / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D018398:Homeodomain Proteins; D006801:Humans; D015778:Minor Histocompatibility Antigens; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism*; D047428:Protein Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D051818:Replication Protein C; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D013698:Templates, Genetic
chemical_list: C096816:BCL2-related protein A1; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004270:DNA, Circular; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C096063:MATA1 protein, S cerevisiae; D015778:Minor Histocompatibility Antigens; D018809:Proliferating Cell Nuclear Antigen; D047428:Protein Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase; D051818:Replication Protein C