Cdc2Hs (also named p34cdc2 or cdk1) is a catalytic subunit of a protein kinase complex, called the M-phase promoting factor, which induces entry into mitosis and is universal among eukaryotes. In the fission yeast Schizosaccharomyces pombe, the gene Cdc2 is responsible for controlling the transition from G1 phase to the S phase and from the G2 phase to the M phase of the cell cycle.