Promotion of sporulation by caffeine pretreatment in Saccharomyces cerevisiae. II. Changes in ribonuclease activity during sporulation.

Changes in RNase activity during sporulation of a homothallic diploid strain of Saccharomyces cerevisiae were measured in caffeine-treated and non-treated cells. 1. In caffeine-treated cells soon after the transfer to the sporulation medium a significant increase in RNase activity was observed; in control cells the rise of RNase activity was less and started after a lag period of 5 h. The final activity of RNase activity was about twice as high in caffeine-treated cells as in control cells. 2. Increase in RNase activity during sporulation was sensitive to cycloheximide in control cells, but insensitive in caffeine-treated cells. 3. RNases from vegetative cells and from sporulating ones are different in their Km values. Relation of the changes in RNase activity to premeiotic DNA synthesis is discussed.