title: Interaction between PCNA and DNA ligase I is critical for joining of Okazaki fragments and long-patch base-excision repair.
abstract: DNA ligase I belongs to a family of proteins that bind to proliferating cell nuclear antigen (PCNA) via a conserved 8-amino-acid motif [1]. Here we examine the biological significance of this interaction. Inactivation of the PCNA-binding site of DNA ligase I had no effect on its catalytic activity or its interaction with DNA polymerase beta. In contrast, the loss of PCNA binding severely compromised the ability of DNA ligase I to join Okazaki fragments. Thus, the interaction between PCNA and DNA ligase I is not only critical for the subnuclear targeting of the ligase, but also for coordination of the molecular transactions that occur during lagging-strand synthesis. A functional PCNA-binding site was also required for the ligase to complement hypersensitivity of the DNA ligase I mutant cell line 46BR.1G1 to monofunctional alkylating agents, indicating that a cytotoxic lesion is repaired by a PCNA-dependent DNA repair pathway. Extracts from 46BR.1G1 cells were defective in long-patch, but not short-patch, base-excision repair (BER). Our results show that the interaction between PCNA and DNA ligase I has a key role in long-patch BER and provide the first evidence for the biological significance of this repair mechanism.
authors.affiliation: Department of Molecular Medicine, Institute of Biotechnology, The University of Texas Health Science Center at San Antonio, 78245, USA.
authors.forename: D S
authors.initials: DS
authors.lastname: Levin
authors.forename: A E
authors.initials: AE
authors.lastname: McKenna
authors.forename: T A
authors.initials: TA
authors.lastname: Motycka
authors.forename: Y
authors.initials: Y
authors.lastname: Matsumoto
authors.forename: A E
authors.initials: AE
authors.lastname: Tomkinson
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D004247:DNA / Q000378:metabolism*; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair; D006801:Humans; D016297:Mutagenesis, Site-Directed; D018809:Proliferating Cell Nuclear Antigen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding
chemical_list: C000607892:LIG1 protein, human; C022262:Okazaki fragments; D018809:Proliferating Cell Nuclear Antigen; D004247:DNA; D011088:DNA Ligases; D000072481:DNA Ligase ATP