Expression of the Yeast UBI4 Gene Increases in Response to DNA-Damaging Agents and in Meiosis

Abstract

The polyubiquitin gene, UBI4, of Saccharomyces cerevisiae is regulated by a variety of environmental stresses and physiological conditions. After exposure of rapidly growing yeast cells to DNA-damaging agents (4-nitroquinoline-1-oxide and N-methyl-N′-nitro-N-nitrosoguanidine), intracellular levels of UBI4 transcript increased rapidly. Induction of UBI4 transcripts occurred within 30 to 60 min of exposure to 4-nitroquinoline-1-oxide in RAD⁺, rad52, and rad6 repair-deficient yeast strains. In high-density RAD⁺ cultures, the effect of alkylating agents on UBI4 transcript levels is attenuated, in part because of significant increases in the basal level of this message in untreated cells. We also observed that the levels of UBI4 transcripts increased significantly when diploid cells were exposed to sporulation conditions. Maximal levels of UBI4 transcripts were reached after 6 to 8 h in sporulation medium. Accumulation of UBI4 transcripts occurred in a/α diploids that undergo meiosis but not in asporogenous α/α diploids exposed to the same nutritional conditions.