Transcription of the cdc2 cell cycle control gene of the fission yeast Schizosaccharomyces pombe.

The cdc2 gene plays a central role in the control of the mitotic cell cycle of the fission yeast Schizosaccharomyces pombe. It is required in G1 at start for commitment to the mitotic cycle and then again in G2 where it determines the timing of mitosis. We have identified the cdc2 gene transcript as a 1.6-kb polyadenylated mRNA. This transcript is generated after four introns have been spliced out; there is no evidence for differential splicing. The level of cdc2 transcript does not change during a shift between cell proliferation and stationary phase or during the mitotic cell cycle. Overproduction of the cdc2 transcript does not alter the normal cell cycle. We conclude that the cell cycle is not controlled by changes in either the cdc2 transcript level or in its processing. A gene adjacent to cdc2 called cdc2L has also been identified. This encodes three transcripts of 1.0-1.3 kb in length, at least two of which are cell cycle regulated. Their levels peak during S-phase and are increased in certain cell cycle mutants. This gene may code for a product which is required for the mitotic cell cycle.