Leucine-zipper transcriptional activator; regulates the sulfur amino acid pathway; requires different combinations of auxiliary factors Cbf1p, Met28p, Met31p and Met32p; specific involvement in sulfur starvation-induced autophagy with Gcn4p; feedforward loop exists in the regulation of genes controlled by Met4p and Met32p; ubiquitinated by SCF-Met30p, leading to either degradation or maintenance in an inactive state; regulates degradation of its DNA-binding cofactors by SCF-Met30p targeting