Substrate overlap and functional competition between human nucleotide excision repair and Escherichia coli photolyase and (a)BC excision nuclease.
Human cell free extract prepared by the method of Manley et al. (1980) carries out repair synthesis on UV-irradiated DNA. Removal of pyrimidine dimers by photoreactivation with DNA photolyase reduces repair synthesis by about 50%. With excess enzyme in the reaction mixture photolyase reduced the repair signal by the same amount even in the absence of photoreactivating light, presumably by binding to pyrimidine dimers and interfering with the binding of human damage recognition protein. Similarly, the UvrB subunit of Escherichia coli (A)BC excinuclease when loaded onto UV-irradiated or psoralen-adducted DNA inhibited repair synthesis by cell-free extract by 75-80%. The opposite was true also as HeLa cell free extract specifically inhibited the photorepair of a thymine dimer by DNA photolyase and its removal by (A)BC excinuclease. Cell-free extracts from xeroderma pigmentosum (XP) complementation groups A and C were equally effective in blocking the E. coli repair proteins, while extracts from complementation groups D and E were ineffective in blocking the E. coli enzyme. These results suggest that XP-D and XP-E cells are defective in the damage recognition subunit(s) of human excision nuclease.
Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill 27599.
Sibghat-Ullah
A
A
Sancar
D001667:Binding, Competitive; D004247:DNA / Q000187:drug effects*; D004260:DNA Repair; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000494:pharmacology*; D004706:Endodeoxyribonucleases / Q000493:pharmacokinetics*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D005816:Genetic Complementation Test; D006367:HeLa Cells; D006801:Humans; D008190:Lyases / Q000494:pharmacology*; D011740:Pyrimidine Dimers / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000201:enzymology; D013379:Substrate Specificity
D029968:Escherichia coli Proteins; D011740:Pyrimidine Dimers; D004247:DNA; D004706:Endodeoxyribonucleases; C036385:endodeoxyribonuclease uvrABC; D008190:Lyases; D004255:Deoxyribodipyrimidine Photo-Lyase