Mechanisms of radiation‐induced gene responses

While identifying genes differentially expressed in cells exposed to ultraviolet 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 coding region and the 3′ untranslated region, the sequence is most frequently in a ‐/+ orientation. The element is found in many different genes that have diverse functions. Gel mobility shift assays demonstrated the presence of a protein in HeLa cell extracts that binds to the sense and antisense single‐stranded consensus oligomers, as well as to double‐stranded oligonucleotide. When double‐stranded oligomer was used, the size shift demonstrated an additional protein‐oligomer complex larger than the one bound to either sense or antisense single‐stranded consensus oligomers alone. This element may bind to protein(s) that maintain DNA in a single‐stranded orientation for transcription, or be important in the transcription‐coupled DNA repair process. Stem Cells 1997; 15 (suppl 2): 15–25