MET31 encodes a DNA-binding protein involved in the transcriptional control of genes involved in sulfur metabolism (1, 4, 5). Transcription of these genes is driven by large multisubunit complexes that assemble on their 5' upstream regions. Depending on the target, different combinations of the Cbf1p, Met28p, Met31p, and Met32p factors are assembled and tether the transcription factor Met4p to the DNA (6, 4, 5). Met31p, itself devoid of any intrinsic transcription activation function, appears not to act during the transcriptional regulation of all of the MET genes, but recruits Met4p to the promoters of some of the methionine biosynthetic genes, and is required for their expression (1, 7, 4). Met31p and Met32p are highly-related (46% identical) zinc finger-containing proteins, each containing an amino-terminal zinc finger of the CC/HH type, and a carboxy-terminal zinc finger of the CC/HC type (1, 8). Both proteins recognize and bind the upstream element 5'-AAACTGTGG-3', and the binding of Cbf1p in the vicinity of this motif enhances this affinity (9). The function of Met31p during the transcriptional regulation of the sulfate assimilation pathway varies from one gene to another, as Met31p seems to function as a negative regulatory factor at the MET25 promoter region, but as an essential positive effector at the MET3 and MET14 promoter regions (1, 8). The function of Met31p is not restricted to these pathways, however, as it is also involved in regulating GSH1 expression in response to cadmium (7), and may play a role in coregulating genes involved in copper and iron metabolism (10).

Last updated: 2003-05-27