title: Structural basis for novel interactions between human translesion synthesis polymerases and proliferating cell nuclear antigen.
abstract: Translesion synthesis (TLS) is a DNA damage tolerance mechanism that allows continued DNA synthesis, even in the presence of damaged DNA templates. Mammals have multiple DNA polymerases specialized for TLS, including Poleta, Poliota, and Polkappa. These enzymes show preferential bypass for different lesions. Proliferating cell nuclear antigen (PCNA), which functions as a sliding clamp for the replicative polymerase Poldelta, also interacts with the three TLS polymerases. Although many PCNA-binding proteins have a highly conserved sequence termed the PCNA-interacting protein box (PIP-box), Poleta, Poliota, and Polkappa have a noncanonical PIP-box sequence. In response to DNA damage, Lys-164 of PCNA undergoes ubiquitination by the RAD6-RAD18 complex, and the ubiquitination is considered to facilitate TLS. Consistent with this, these three TLS polymerases have one or two ubiquitin binding domains and are recruited to replication forks via interactions with ubiquitinated PCNA involving the noncanonical PIP-box and ubiquitin binding domain. However, it is unclear how these TLS polymerases interact with PCNA. To address the structural basis for interactions between different TLS polymerases and PCNA, we determined crystal structures of PCNA bound to peptides containing the noncanonical PIP-box of these polymerases. We show that the three PIP-box peptides interact with PCNA in different ways, both from one another and from canonical PIP-box peptides. Especially, the PIP-box of Poliota adopts a novel structure. Furthermore, these structures enable us to speculate how these TLS polymerases interact with Lys-164-monoubiquitinated PCNA. Our results will provide clues to understanding the mechanism of preferential recruitment of TLS polymerases to the stalled forks.
authors.affiliation: International Graduate School of Arts and Sciences, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Asami
authors.initials: A
authors.lastname: Hishiki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hashimoto
authors.forename: Tomo
authors.initials: T
authors.lastname: Hanafusa
authors.forename: Keijiro
authors.initials: K
authors.lastname: Kamei
authors.forename: Eiji
authors.initials: E
authors.lastname: Ohashi
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Shimizu
authors.forename: Haruo
authors.initials: H
authors.lastname: Ohmori
authors.forename: Mamoru
authors.initials: M
authors.lastname: Sato
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018360:Crystallography, X-Ray; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D018809:Proliferating Cell Nuclear Antigen / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D016415:Sequence Alignment
chemical_list: D007527:Isoenzymes; D018809:Proliferating Cell Nuclear Antigen; D004259:DNA-Directed DNA Polymerase