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. Author manuscript; available in PMC: 2014 Dec 1.
Published in final edited form as: Curr Opin Cell Biol. 2013 Aug 2;25(6):10.1016/j.ceb.2013.07.010. doi: 10.1016/j.ceb.2013.07.010

Figure 1.

Figure 1

Despite a lack of sequence homology, G1 control networks are similar in both yeast (left panel) and mammals (right panel). Proteins and signals with similar functions are similarly shaped/colored. Upstream growth cues activate G1 cyclins, which drive progression into S phase via the activation of a positive feedback loop. Differentiation signals, including the pheromone-activated MAPK pathway in yeast, activate proteins that inhibit cyclin-CDK activity, leading to the increased stability of a low CDK activity cellular state.