title: Replication of a cis-syn thymine dimer at atomic resolution.
abstract: Ultraviolet light damages DNA by catalysing covalent bond formation between adjacent pyrimidines, generating cis-syn cyclobutane pyrimidine dimers (CPDs) as the most common lesion. CPDs block DNA replication by high-fidelity DNA polymerases, but they can be efficiently bypassed by the Y-family DNA polymerase pol eta. Mutations in POLH encoding pol eta are implicated in nearly 20% of xeroderma pigmentosum, a human disease characterized by extreme sensitivity to sunlight and predisposition to skin cancer. Here we have determined two crystal structures of Dpo4, an archaeal pol eta homologue, complexed with CPD-containing DNA, where the 3' and 5' thymine of the CPD separately serves as a templating base. The 3' thymine of the CPD forms a Watson-Crick base pair with the incoming dideoxyATP, but the 5' thymine forms a Hoogsteen base pair with the dideoxyATP in syn conformation. Dpo4 retains a similar tertiary structure, but each unusual DNA structure is individually fitted into the active site for catalysis. A model of the pol eta-CPD complex built from the crystal structures of Saccharomyces cerevisiae apo-pol eta and the Dpo4-CPD complex suggests unique features that allow pol eta to efficiently bypass CPDs.
authors.affiliation: Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Ling
authors.forename: François
authors.initials: F
authors.lastname: Boudsocq
authors.forename: Brian S
authors.initials: BS
authors.lastname: Plosky
authors.forename: Roger
authors.initials: R
authors.lastname: Woodgate
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry / Q000378:metabolism; D020029:Base Pairing; D001483:Base Sequence; D001665:Binding Sites; D003460:Crystallization; D004249:DNA Damage; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011740:Pyrimidine Dimers / Q000096:biosynthesis* / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D012996:Solutions; D013329:Structure-Activity Relationship; D016944:Sulfolobus / Q000201:enzymology*; D013698:Templates, Genetic; D000099270:Y-Family DNA Polymerases
chemical_list: D019843:Archaeal Proteins; D004259:DNA-Directed DNA Polymerase; D011740:Pyrimidine Dimers; D012996:Solutions; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases