Identification of the DNA damage-responsive elements of the rhp51⁺ gene, a recA and RAD51 homolog from the fission yeast Schizosaccharomyces pombe

The Schizosaccharomyces pombe rhp51⁺ gene encodes a recombinational repair protein that shares significant sequence identities with the bacterial RecA and the Saccharomyces cerevisiae RAD51 protein. Levels of rhp51⁺ mRNA increase following several types of DNA damage or inhibition of DNA synthesis. An rhp51::ura4 fusion gene was used to identify the cis-acting promoter elements involved in regulating rhp51⁺ expression in response to DNA damage. Two elements, designated DRE1 and DRE2 (for damage-responsive element), match a decamer consensus URS (upstream repressing sequence) found in the promoters of many other DNA repair and metabolism genes from S. cerevisiae. However, our results show that DRE1 and DRE2 each function as a UAS (upstream activating sequence) rather than a URS and are also required for DNA-damage inducibility of the gene. A 20-bp fragment located downstream of both DRE1 and DRE2 is responsible for URS function. The DRE1 and DRE2 elements cross-competed for binding to two proteins of 45 and 59 kDa. DNase I footprint analysis suggests that DRE1 and DRE2 bind to the same DNA-binding proteins. These results suggest that the DRE-binding proteins may play an important role in the DNA-damage inducibility of rhp51⁺ expression.