INVESTIGATION
Among B-Type Cyclins Only CLB5 and CLB6 Promote
Premeiotic S Phase in Saccharomyces cerevisiae
James M. DeCesare1 and David T. Stuart2
Department of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
ABSTRACT The Saccharomyces cerevisiae cyclin Clb5 is required for premeiotic S phase, meiotic recombination, and successful
progression through meiosis. Clb5 is not essential for mitotic proliferation because Clb1–Clb4 can support DNA replication in clb5
clb6 mutants. Clb1, Clb3, and Clb4 accumulate in clb5 clb6 cells during meiotic differentiation yet fail to promote premeiotic DNA
replication. When expressed under the regulation of the CLB5 promote