Protein Patterns during Sporulation in Fission Yeast

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Abstract
Various strains (wild-type and mutants) of Schizosaccharomyces pombe were subjected to sporulation conditions, and analysed with regard to changes in their protein patterns. Trisbuffer-soluble proteins (TS) and DNA-binding proteins (DB) were denatured and separated by polyacrylam ide electrophoresis. A fter endogenous nitrogen depletion (the apparent trigger of conjuga­tion and sporulation) the following alterations were observed: larger TS-proteins were proteolytical-ly degraded; the pattern of DB-proteins underwent several selective changes (reduction, enforce­ ment, or new appearance of individual bands) ; an endonucleolytic DNase activity appeared. Most of these changes were expressed before conjugation, and did not appear in sterile strains. They could, however, be provoked by an abrupt shift to nitrogen-free medium, even in sterile strains. Inhibition studies with cycloheximide revealed at least two phases of protein synthesis specifically needed for sporulation: a very sensitive phase before conjugation, and a more resistant phase lasting until 0.5 h before spore form ation. Medium exchange between heterothallic cultures (h+ and h-) effected certain sporulation-specific alterations of the DB-protein pattern, indicative of diffusible mating-type factors in the culture fluid.

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