S-phase promoting factor

Three Gi Cyclins Associate with S. cerevisiae CDK to form S Phase-Promoting Factors... 

B-type cyclin required to activate the catalytic subunit. By analogy, it seemed likely that 5. cerevisiae contains an S phase-promoting factor (SPF) that phosphorylates and regulates proteins required for DNA synthesis. Similar to MPF, SPF was proposed to be a heterodimer composed of the S. cerevisiae CDK and a cyclin, in this case one that acts in Gi (see Figure 21-2, steps [2]- 4]). 

Interphase 854 meiosis 890 mitogens 856 mitosis-promoting factor (MPF) 860 mitotic cyclln 861 p53 protein 889 quiescent cells 883 Rb protein 884 restriction point 883 S-phase inhibitor 868 S phase-phase promoting factor (SPF) 876 securln 872 synapsis 892 Weel protein-tyrosine kinase 866... 

Borgne, A, Ostvold, A. C., Flament, S., Meijer, L. (1999). Intra-M phase-promoting factor phosphorylation of cyclin B at the prophase/ metaphase transition. The Journal of Biological Chemistry, 274, 11977-11986. 

Cell Cycle Control. Figure 1 Cell cycle regulation by Cyclin dependent kinases (CDKs). Different cyclins bound to different CDKs promote the transition from one cell cycle phase into another. CDK-dependent phosphorylation of Rb is required to release active E2F transcription factors, which promotes entry into S phase. 

MAPK proteins, which in turn are activated by different MAP kinase pathways (see Fig. 10.4). Much of the mitogenic effects of ERK signals can be explained by the observation that ERK-induced expression of transcription factors stimulates the transcription of D-type cyclins, which promotes the Gl/S-phase transition in the cell cycle (see Section 13.4.1). Furthermore, phosphorylation of the CTD of RNA polymerase II (see Section 1.4.3.4) has also been reported to be mediated by the ERK1/2 proteins. 

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