MECHANISMS OF RADIATION-INDUCED GENE RESPONSES

While identifying genes differentially expressed in cells exposed to u ltraviolet radiation, we identified a transcript with a 25-nucleotide region that is highly conserved among a variety of species, including Bacillus circulans, pumpkin, yeast, Drosophila, mouse, and man. In the 5' untranslated region of a gene, the sequence is predominantly in a +/+ orientation with respect to the coding DNA strand; while in the co ding region and the 3' untranslated region, the sequence is most frequ ently in a -/+ orientation. The element is found in many different gen es that have diverse functions. Gel mobility shift assays demonstrated the presence of a protein in HeLa cell extracts that binds to the sen se and antisense single-stranded consensus oligomers, as well as to do uble-stranded oligonucleotide. When double-stranded oligomer was used, the size shift demonstrated an additional protein-oligomer complex la rger than the one bound to either sense or antisense single-stranded c onsensus oligomers alone. This element may bind to protein(s) that mai ntain DNA in a single-stranded orientation for transcription, or be im portant in the transcription-coupled DNA repair process.