title: Replication-dependent and -independent responses of RAD18 to DNA damage in human cells.
abstract: Postreplication repair facilitates tolerance of DNA damage during replication, overcoming termination of replication at sites of DNA damage. A major post-replication repair pathway in mammalian cells is translesion synthesis, which is carried out by specialized polymerase(s), such as polymerase eta, and is identified by focus formation by the polymerase after irradiation with UVC light. The formation of these foci depends on RAD18, which ubiquitinates PCNA for the exchange of polymerases. To understand the initial processes in translesion synthesis, we have here analyzed the response to damage of RAD18 in human cells. We find that human RAD18 accumulates very rapidly and remains for a long period of time at sites of different types of DNA damage, including UVC light-induced lesions, and x-ray microbeam- and laser-induced single-strand breaks, in a cell cycle-independent manner. The accumulation of RAD18 at DNA damage is observed even when DNA replication is inhibited, and a small region containing a zinc finger motif located in the middle of RAD18 is essential and sufficient for the replication-independent damage accumulation. The zinc finger motif of RAD18 is not necessary for UV-induced polymerase eta focus formation, but another SAP (SAF-A/B, Acinus and PIAS) motif near the zinc finger is required. These data indicate that RAD18 responds to DNA damage in two distinct ways, one replication-dependent and one replication-independent, involving the SAP and zinc finger motifs, respectively.
authors.affiliation: Department of Molecular Genetics, Institute of Development, Aging and Cancer, Tohoku University, Sendai 980-8575, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nakajima
authors.forename: Li
authors.initials: L
authors.lastname: Lan
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Kanno
authors.forename: Noriko
authors.initials: N
authors.lastname: Usami
authors.forename: Katsumi
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Masahiko
authors.initials: M
authors.lastname: Mori
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Shiomi
authors.forename: Akira
authors.initials: A
authors.lastname: Yasui
mesh_terms: D002453:Cell Cycle / Q000528:radiation effects; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000528:radiation effects*; D004260:DNA Repair; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase; D006367:HeLa Cells / Q000378:metabolism / Q000528:radiation effects; D006801:Humans; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases; D014466:Ultraviolet Rays; D014965:X-Rays; D016335:Zinc Fingers
chemical_list: D004268:DNA-Binding Proteins; D018809:Proliferating Cell Nuclear Antigen; C485954:RAD18 protein, human; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases; D004259:DNA-Directed DNA Polymerase