RPH1 and GIS1 are damage-responsive repressors of PHR1

Saccharomyces cerevisiae DNA repair gene PHR1 encodes a photolyase that cat alyzes the light-dependent repair of pyrimidine dimers, PHR1 expression is induced at the level of transcription by a variety of DNA-damaging agents. The primary regulator of the PHR1 damage response is a 39-bp sequence calle d URSPHR1 which is the binding site for a protein(s) that constitutes the d amage-responsive repressor PRP. In this communication, we report the identi fication of two proteins, RDh1p and Gis1p, that regulate PHR1 expression th rough URSPHR1. Both proteins contain two putative zinc fingers that are ide ntical throughout the DNA binding region, and deletion of both RPH1 and GIS 1 is required to fully derepress PHR1 in the absence of damage. Derepressio n of PHR1 increases the rate and extent of photoreactivation in vivo, demon strating that the damage response of PHR1 enhances cellular repair capacity . In vitro footprinting and binding competition studies indicate that the s equence AG(4) (C4T) within URSPHR1 is the binding site for RDh1p and Gis1p and suggests that at least one additional DNA binding component is present in the PRP complex.