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Title: UV-induced formation of pyrimidine dimers in nucleosome core DNA is strongly modulated with a period of 10. 3 bases

We have determined the distribution of the major UV-induced photoproducts in nucleosome core DNA using the 3'----5' exonuclease activity of T4 DNA polymerase, which has been shown to stop digestion immediately 3' to UV-induced pyrimidine dimers. This assay is extremely sensitive since all DNA fragments without photoproducts (background) are reduced to small oligonucleotides, which can be separated from those fragments containing photoproducts. The results show that the distribution of UV-induced photoproducts (primarily cyclobutane dipyrimidines) is not uniform throughout core DNA but displays a striking 10.3 (+/- 0.1) base periodicity. Furthermore, this characteristic distribution of photoproducts was obtained regardless of whether nucleosome core DNA was isolated from UV-irradiated intact chromatin fibers, histone H1-depleted chromatin fibers, isolated mononucleosomes, or cells in culture. The yield of pyrimidine dimers along the DNA seems to be modulated in a manner that reflects structural features of the nucleosome unit, possibly core histone-DNA interactions, since this pattern was not obtained for UV-irradiated core DNA either free in solution or bound tightly to calcium phosphate crystals. Based on their location relative to DNase I cutting sites, the sites of maximum pyrimidine dimer formation in core DNA mapped to positions where the phosphate backbone is farthest from the coremore » histone surface. These results indicate that within the core region of nucleosomes, histone-DNA interactions significantly alter the quantum yield of cyclobutane dipyrimidines, possibly by restraining conformational changes in the DNA helix required for formation of these photoproducts.« less
Authors:
; ;
Publication Date:
OSTI Identifier:
5624982
Resource Type:
Journal Article
Resource Relation:
Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States); Journal Volume: 84:19
Research Org:
Washington State Univ., Pullman
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; DNA; CHEMICAL RADIATION EFFECTS; PYRIMIDINE DIMERS; RADIOINDUCTION; CATTLE; CHROMATIN; DNA POLYMERASES; NUCLEOSOMES; ULTRAVIOLET RADIATION; ANIMALS; CHEMISTRY; DOMESTIC ANIMALS; ELECTROMAGNETIC RADIATION; ENZYMES; MAMMALS; NUCLEIC ACIDS; NUCLEOTIDYLTRANSFERASES; ORGANIC COMPOUNDS; PHOSPHORUS-GROUP TRANSFERASES; POLYMERASES; RADIATION CHEMISTRY; RADIATION EFFECTS; RADIATIONS; RUMINANTS; TRANSFERASES; VERTEBRATES 560120* -- Radiation Effects on Biochemicals, Cells, & Tissue Culture