Binding of transcription factors creates hot spots for UV photoproducts in vivo.
Cyclobutane dipyrimidines and less than mean value of 6-4 dipyrimidines are the two major classes of mutagenic DNA photoproducts produced by UV irradiation of cells. We developed a method to map cyclobutane dipyrimidines at the DNA sequence level in mammalian cells. The frequency of this class of photoproducts was determined at every dipyrimidine along the human phosphoglycerate kinase-1 (PGK1) promoter sequence and was compared to the UV-induced frequency distribution of mean value of 6-4 dipyrimidines. After irradiation of living cells containing active or inactive PGK1 genes, enzymatic or chemical cleavage at UV photoproducts, and amplification by ligation-mediated polymerase chain reaction, photofootprints were seen in all regions which bind transcription factors and appear as DNase I footprints. Photoproduct frequency within transcription factor binding sites was suppressed or enhanced relative to inactive genes or naked DNA with enhancements of up to 30-fold. Since photoproducts are mutagenic, this indicates that photoproduct (mutation?) hot spots may be tissue specific in mammals.
Pfeifer
G P
GP
Department of Biology, Beckman Research Institute of the City of Hope, Duarte, California 91010.
Drouin
R
R
Riggs
A D
AD
Holmquist
G P
GP
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D002874:Chromosome Mapping; D006224:Cricetinae; D003503:Cyclobutanes; D004249:DNA Damage / Q000187:drug effects; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis / Q000235:genetics*; D010735:Phosphoglycerate Kinase / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011740:Pyrimidine Dimers; D014157:Transcription Factors / Q000378:metabolism* / Q000494:pharmacology; D014466:Ultraviolet Rays / Q000009:adverse effects*
D003503:Cyclobutanes; D011740:Pyrimidine Dimers; D014157:Transcription Factors; D010735:Phosphoglycerate Kinase