title: Effects of cytosine methylation on pyrimidine dimer formation in DNA.
abstract: The relative induction of cyclobutane pyrimidine dimers (CPD) and pyrimidine (6-4)pyrimidone photoproducts ([6-4]PD) was quantified in the duplex homopolymers polydeoxyadenosine:polydeoxythymidine, polydeoxyguanosine:polydeoxycytidine and polydeoxyguanosine:polydeoxy-5-methylcytidine irradiated with UVC or UVB radiation. Cytosine methylation significantly increased the yield of cytosine (6-4)PD after irradiation with UVC light and of cytosine CPD and (6-4)PD after irradiation with UVB light. The data suggest that CPD and (6-4)PD are preferentially induced at 5-methylcytosine bases in DNA of cells exposed to sunlight and comprise a major component of the mutation spectrum leading to the initiation of sunlight-induced skin cancer.
authors.affiliation: Department of Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Smithville 78957, USA. dmitch@io.com
authors.forename: D L
authors.initials: DL
authors.lastname: Mitchell
mesh_terms: D003596:Cytosine; D004247:DNA / Q000737:chemistry* / Q000528:radiation effects*; D019175:DNA Methylation; D011089:Polydeoxyribonucleotides / Q000737:chemistry / Q000528:radiation effects*; D011740:Pyrimidine Dimers / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D011089:Polydeoxyribonucleotides; D011740:Pyrimidine Dimers; D003596:Cytosine; D004247:DNA