Roadmap highlighting the relationship between the SCFMet30
-Met4 interplay and the regulatory schemes involved in sulfur assimilation, oxidative stress and cell division. The model emphasizes the notion that the SCFMet30 ubiquitin ligase activates the Met4 transcriptional activator in a manner linked to cell division and dependent on low levels of methionine, allowing expression of the MET and SAM genes encoding the enzymes assimilating sulfur into methionine and S-adenosyl-methionine, respectively (green). In a negative feedback response driven by methionine accumulation, with the biosynthesis of S-adenosyl-methionine and cysteine necessary in this regulatory context, Met4 activation by SCFMet30 is blocked, leading to Met4 inhibition (purple). Navy blue indicates steps involved in oxidative stress response induced by cadmium (Cd2+). Note that Sam1 and Sam2 enzymes are necessary for all three types of responses, emphasizing the special regulatory role of S-adenosyl-methionine biosynthesis. Methionine, S-adenosyl-methionine and cysteine are necessary for the biosynthesis and modification of proteins, lipids and nucleotides during growth (turquoise). See text for details.