CLONING AND CHARACTERIZATION OF RAD17, A GENE CONTROLLING CELL-CYCLE RESPONSES TO DNA-DAMAGE IN SACCHAROMYCES-CEREVISIAE

Mutants of the yeast Saccharomyces cerevisiae defective in the RAD17 g ene are sensitive to ultraviolet (UV) and gamma radiation and manifest a defect in G(2) arrest following radiation treatment. We have cloned the RAD17 gene by complementation of the UV sensitivity of a rad17-1 mutant and identified an ORF of 1.2 kb encoding a predicted gene produ ct of 45.4 kDa with homology to the Schizosaccharomyces pombe rad1(+) gene product and to Ustilago maydis Red, a known 3'-->5' exonuclease. The RAD17 transcript is cell cycle regulated, with maximum steady-stat e levels during late G(1). The rad17-1 mutation represents a missense mutation that maps to a conserved region of the gene. A rad17 disrupti on mutant grows normally and manifests levels of UV sensitivity simila r that of the rad17-1 strain. As previously observed with other genes involved in G(2) arrest (such as RADS and RAD24), RAD17 regulates radi ation-induced G(1) checkpoints at at least two possible arrest stages. One is equivalent to or upstream of START, the other at or downstream of the Cdc4 execution point. However, the temperature sensitivity of the cell cycle mutant dna1-1 (a G(1) arrest mutant) is not influenced by inactivation of RAD17.