ADDITIONAL DELAY IN SPORULATION IN SACCHAROM YCES CEREVISIAE CAUSED BY PROTEIN SYNTHESIS INHIBITORS: EVIDENCE FOR SYNTHESIS OF LABILE PROTEIN CONTROLLING SPORULATION

Abstract

Effects of inhibitors of protein synthesis on sporulation in Saccharomyces cerevisiae were analyzed kinetically to determine whether the sporulation requires the synthesis of short-lived proteins (labile proteins). Pulse-treatment with cycloheximide at low concentrations (0.1-10μM) caused marked delay in spore formation without any significant effect on sporulation synchrony. The delay in spore formation greatly exceeded the length of pulses. A similar effect on spore formation was caused by treatment with puromycin. The delay in spore formation was brought about only by cycloheximide pulses carrried out during meiosis I. In the pulse-treated cells, meiotic progression during meiosis I was markedly delayed. The subsequent meiotic progression to telophase II proceeded without any significant delay, but the duration of spore wall formation after the progression to telophase II was prolonged. The increase in activities of fumarase and malate synthase which occurred during meiosis I was not affected by the cycloheximide pulse, and the levels of those activities were retained rather more stably in pulsetreated cells than in untreated cells. These results suggest that labile proteins are synthesized during meiosis I and play some roles during meiosis 1 in the progression of meiosis and in the events preparatory for spore wall formation.