Gl cyclin

For the G1 cyclins in yeast, it is assumed that they are phosphorylated in an autocataly-tic process by the activated Gl-cyclin-CDK complex and are thus marked for degradation. According to this mechanism, the G1 cyclins are subject to continual degradation, which would explain their short half-hfe. 

A. Amon, M. Tyers, B. Futcher, and K. Nasmyth. Mechanisms that help the yeast cell cycle clock tick G2 cyclins transcriptionally activate G2 cyclins and repress Gl cyclins. Cell, 74 (6), 993-1007, 1993. 

The cyclin proteins appear to play a major role in cell cycle regulation 79). Cyclins are a family of proteins that accumulate in the G1 phase (Gl-cyclins), and again during late S-G2 phases before mitosis (mitotic cyclins) 80). After they reach a peak concentration, cyclin proteins are rapidly degraded. 

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