REGULATION OF THE SACCHAROMYCES-CEREVISIAE DNA-REPAIR GENE RAD16

The RAD16 gene product has been shown to be essential for the repair o f the silenced mating type loci [Bang et al. (1992) Nucleic Acids Res. 20, 3925-3931]. More recently we demonstrated that the RAD16 and RAD7 proteins are also required for repair of non-transcribed strands of a ctive genes in Saccharomyces cerevisiae [Waters et al. (1993) Mel. Gen . Genet 239, 28-32], We have studied the regulation of the RAD16 gene and found that the RAD16 transcript levels increased up to 7-fold upon UV irradiation. Heat shock at 42 degrees C also results in elevated l evels of RAD16 mRNA. in sporulating MAT alpha/MATa diploid cells RAD16 mRNA is also induced. The basal level of the RAD16 transcript is cons tant during the mitotic cell cycle. G1-arrested cells show normal indu ction of RAD16 mRNA upon UV irradiation demonstrating that the inducti on is not a secondary consequence of G2 cell cycle arrest following UV irradiation. However, in cells arrested in G1 the induction of RAD16 mRNA after UV irradiation is not followed by a rapid decline as occurs in normal growing cells suggesting that the down regulation of RAD16 transcription is dependent on progression into the cell cycle.