UV induced (6-4) photoproducts are distributed differently than cyclobutane dimers in nucleosomes.
We have compared the distributions of two stable UV photoproducts in nucleosome core DNA at the single-nucleotide level using a T4 polymerase-exonuclease mapping procedure. The distribution of pyrimidine-pyrimidone (6-4) dimers was uncovered by reversing the major UV photo-product, cis-syn cyclobutane pyrimidine dimer, with E. coli DNA photolyase and photoreactivating light. Whereas the distribution of total UV photoproducts in nucleosome core DNA forms a striking 10.3 base periodic pattern, the distribution of (6-4) dimers is much more random throughout the nucleosome core domain. Therefore, histone-DNA interactions in nucleosomes strongly modulate formation of the major class of UV-induced photoproducts, while having either a constant effect or no effect on (6-4) dimer formation.
Gale
J M
JM
Biochemistry/Biophysics Program, Washington State University, Pullman 99164-4660.
Smerdon
M J
MJ
D000818:Animals; D002417:Cattle; D002843:Chromatin / Q000528:radiation effects; D004247:DNA / Q000528:radiation effects*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D005092:Exonucleases / Q000378:metabolism; D009707:Nucleosomes / Q000528:radiation effects*; D009710:Nucleotide Mapping; D013604:T-Phages / Q000201:enzymology; D013950:Thymus Gland / Q000528:radiation effects; D014466:Ultraviolet Rays
D002843:Chromatin; D009707:Nucleosomes; D004247:DNA; D004259:DNA-Directed DNA Polymerase; D005092:Exonucleases