Transcriptional Regulation of the Copper Transporter Mfc1 in Meiotic Cells

Mfc1 is a meiosis-specific protein that mediates copper transport during the meiotic program inSchizosaccharomyces pombe . Although themfc1 + gene is induced at the transcriptional level in response to copper deprivation, the molecular determinants that are required for its copper starvation-dependent induction are unknown. Promoter deletion and site-directed mutagenesis have allowed identification of a newcis -regulatory element in the promoter region of themfc1 + gene. Thiscis -acting regulatory sequence containing the sequence TCGGCG is responsible for transcriptional activation ofmfc1 + under low-copper conditions. The TCGGCG sequence contains a CGG triplet known to serve as a binding site for members of the Zn(2) Cys(6) binuclear cluster transcriptional regulator family. In agreement with this fact, one member of this group of regulators, denoted Mca1, was found to be required for maximum induction ofmfc1 + gene expression. Analysis of Mca1 cellular distribution during meiosis revealed that it colocalizes with both chromosomes and sister chromatids during early, middle, and late phases of the meiotic program. Cells lacking Mca1 exhibited a meiotic arrest at metaphase I under low-copper conditions. Binding studies revealed that the N-terminal 150-residue segment of Mca1 expressed as a fusion protein inEscherichia coli specifically interacts with the TCGGCG sequence of themfc1 + promoter. Taken together, these results identify thecis -regulatory TCGGCG sequence and the transcription factor Mca1 as critical components for activation of the meiotic copper transportmfc1 + gene in response to copper starvation.