title: Asymmetry of DNA replication and translesion synthesis of UV-induced thymine dimers.
abstract: In vitro replication assays for detection and quantification of bypass of UV-induced DNA photoproducts were used to compare the capacity of extracts prepared from different human cell lines to replicate past the cis,syn cyclobutane thymine dimer ([c,s]TT). The results demonstrated that neither nucleotide excision repair (NER) nor mismatch repair (MMR) activities in the intact cells interfered with measurements of bypass replication efficiencies in vitro. Extracts prepared from HeLa (NER- and MMR-proficient), xeroderma pigmentosum group A (NER-deficient), and HCT116 (MMR-deficient) cells displayed similar capacity for translesion synthesis, when the substrate carried the site-specific [c,s]TT on the template for the leading or the lagging strand of nascent DNA. Extracts from xeroderma pigmentosum variant cells, which lack DNA polymerase eta, were devoid of bypass activity. Bypass-proficient extracts as a group (n=16 for 3 extracts) displayed higher efficiency (P=0.005) for replication past the [c,s]TT during leading strand synthesis (84+/-22%) than during lagging strand synthesis (64+/-13%). These findings are compared to previous results concerning the bypass of the (6-4) photoproduct [Biochemistry 40 (2001) 15215] and analyzed in the context of the reported characteristics of bypass DNA polymerases implicated in translesion synthesis of UV-induced DNA lesions. Models to explain how these enzymes might interact with the DNA replication machinery are considered. An alternative pathway of bypass replication, which avoids translesion synthesis, and the mutagenic potential of post-replication repair mechanisms that contribute to the duplication of the human genome damaged by UV are discussed.
authors.affiliation: Department of Pathology and Laboratory Medicine, Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina,Chapel Hill, NC 27599-7525, USA. uncmcs@med.unc.edu
authors.forename: Marila
authors.initials: M
authors.lastname: Cordeiro-Stone
authors.forename: Nana
authors.initials: N
authors.lastname: Nikolaishvili-Feinberg
mesh_terms: D002460:Cell Line; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication; D006367:HeLa Cells; D006801:Humans; D008954:Models, Biological; D016296:Mutagenesis; D011740:Pyrimidine Dimers / Q000378:metabolism* / Q000528:radiation effects*; D014466:Ultraviolet Rays / Q000009:adverse effects; D014983:Xeroderma Pigmentosum / Q000235:genetics / Q000378:metabolism
chemical_list: D011740:Pyrimidine Dimers