Crosslinking of the complementary strands of DNA by UV light: dependence on the oligonucleotide composition of the UV irradiated DNA

UV light crosslinks the complementary strands of DNA. The interstrand cross links may contribute to the biological and pathological effects that UV irr adiation is known to bring about. Here alkaline agarose gel electrophoresis was used to assess the crosslinked fraction of 31 selected restriction fra gments of six viral and plasmid DNA molecules exposed to UVC light irradiat ion. As many as 17 independent experiments were performed with the particul ar DNA fragments to get sufficiently precise data suitable for quantitative analyses. The data were used to determine how the crosslinked fraction dep ended on the dinucleotide, trinucleotide and tetranucleotide contents of th e irradiated DNA fragments. This analysis demonstrated that DNA conformatio n and/or flexibility, rather than the local double helix thermostability, g overned the phenomenon of crosslinking. For example, (GA). (TC) suppressed the crosslink formation in DNA more than any dinucleotide composed of only G and C. In addition, (CTAG). (CTAG) promoted crosslinking much more than a ny other tetranucleotide, including e.g. (TATA). (TATA), whereas the closel y related (CATG). (CATG) belonged among the tetranucleotides that most supp ressed the UV light induced crosslinks between the complementary strands of DNA. The present data reproduced crosslinking of the analyzed 31 restricti on fragments with a correlation coefficient exceeding 0.90. This result wil l be useful to predict crosslinking along the whole human genome. (C) 2001 Elsevier Science B.V. All rights :reserved.