Transcriptional Regulation of the Copper Transporter Mfc1 in Meiotic Cells

Abstract

Mfc1 is a meiosis-specific protein that mediates copper transport during the meiotic program in Schizosaccharomyces pombe. Although the mfc1؉ 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 new cis-regulatory element in the promoter region of the mfc1 ؉ gene. This cis-acting regulatory sequence containing the sequence TCGGCG is responsible for transcriptional activation of mfc1 ؉ 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 (

Copper transport and regulation in Schizosaccharomyces pombe

“…Secondly, whereas the deletion of cuf1 + ( cuf1 Δ) impairs the induction of ctr4 + , activation of mfc1 + is unaffected, suggesting the existence of a distinct transcriptional regulator for the induction of mfc1 + in response to copper starvation [28]. Analysis of promoter regions in mfc1 + has revealed that two TCGGCG regulatory elements containing CGG triplets are responsible for transcriptional activation of mfc1 + under low-copper conditions [38]. Consistent with the fact that cis -acting elements containing CGG triplets are known to serve as binding sites for members of the Zn 2 Cys 6 binuclear cluster class of regulators [39], Mca1 (a Zn 2 Cys 6 cluster-type transcription factor) was found to be necessary for maximum induction of mfc1 + gene expression [38].…”

“…Analysis of promoter regions in mfc1 + has revealed that two TCGGCG regulatory elements containing CGG triplets are responsible for transcriptional activation of mfc1 + under low-copper conditions [38]. Consistent with the fact that cis -acting elements containing CGG triplets are known to serve as binding sites for members of the Zn 2 Cys 6 binuclear cluster class of regulators [39], Mca1 (a Zn 2 Cys 6 cluster-type transcription factor) was found to be necessary for maximum induction of mfc1 + gene expression [38]. Both mfc1 Δ and mca1 Δ mutant strains display phenotypes linked to copper starvation.…”

“…For example, under copper-limiting conditions, mfc1 Δ/ mfc1 Δ mutant cells exhibit a meiotic progression that is delayed and prolonged (by ~2–3 h) compared with the wild-type strain. Under the same copper-limiting conditions, cells lacking Mca1 ( mca1 Δ/ mca1 Δ mutants) undergo a meiotic arrest at metaphase I that blocks cellular differentiation [38]. These observations suggest that Mca1 may play an important role in activation of other meiotic genes aside from mfc1 + , especially those expressed in early meiosis that precedes metaphase I.…”

“…On the basis of previous studies on Zn 2 Cys 6 cluster-type transcription factors, it can be suggested that the zinc-finger motif, the linker and the dimerization region form the putative N-terminal DNA-binding domain of Mca1 (residues 1–138). Binding studies have revealed that the N-terminal 150-residue segment of Mca1 (including residues 1–138) specifically recognizes the TCGGCGN 13 TCGGCG sequence of the mfc1 + promoter region [38]. Given the fact that two zinc-finger units are required to bind a pair of CGG triplets, this restriction implies that Mca1 may bind the TCGGCGN 13 TCGGCG sequence as a homodimer.…”

An Antisense RNA-mediated Mechanism Eliminates a Meiosis-specific Copper-regulated Transcript in Mitotic Cells

“…Synchronous meiosis of pat1-114/pat1-114 diploid cells was carried out as described previously (28). Treatments of meiotic cells were performed using low concentrations of TTM (150 M) and CuSO 4 (50 M) as described previously (30). Monitoring progression of meiotic cells throughout the differentiation program was performed as described previously (31).…”