The yeast ubiquitin ligase SCF Met30 : connecting environmental and intracellular conditions to cell division

Ubiquitination regulates a host of cellular processes and is well known for its role in progression through the cell division cycle. In budding yeast, cadmium and arsenic stress, the availability of sulfur containing amino acids, and the intracellular concentration of S-adenosylmethionine are linked to cell cycle regulation through the ubiquitin ligase SCF Met30 . Regulation is achieved by ubiquitination of the transcription factor Met4. Met4 activity is controlled by a regulatory K48-linked ubiquitin chain that is synthesized by Cdc34/SCF Met30 . A ubiquitin-interacting-motif (UIM) present in Met4 prevents degradation of ubiquitinated Met4 allowing the ubiquitin chain to function as a reversible switch of Met4 activity. Here we discuss mechanisms of Met4 and SCF Met30 regulation in response to intracellular and environmental conditions, and describe the integration of these signals with cell cycle control.