Beaudoin Jude, Ioannoni Raphaël, Mailloux Stéphane, Plante Samuel, Labbé Simon
Département de Biochimie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada.
Eukaryot Cell. 2013 Apr;12(4):575-90. doi: 10.1128/EC.00019-13. Epub 2013 Feb 8.
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(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 of mfc1(+) 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 in Escherichia coli specifically interacts with the TCGGCG sequence of the mfc1(+) promoter. Taken together, these results identify the cis-regulatory TCGGCG sequence and the transcription factor Mca1 as critical components for activation of the meiotic copper transport mfc1(+) gene in response to copper starvation.
Mfc1是一种减数分裂特异性蛋白，在粟酒裂殖酵母的减数分裂过程中介导铜转运。尽管mfc1(+)基因在转录水平上因铜缺乏而被诱导，但尚不清楚其铜饥饿依赖性诱导所需的分子决定因素。启动子缺失和定点诱变已使得在mfc1(+)基因的启动子区域鉴定出一种新的顺式调控元件。这个包含TCGGCG序列的顺式作用调控序列负责在低铜条件下mfc1(+)的转录激活。TCGGCG序列包含一个已知作为Zn(2)Cys(6)双核簇转录调节因子家族成员结合位点的CGG三联体。与此事实一致，发现该调节因子组的一个成员，即Mca1，是mfc1(+)基因表达最大诱导所必需的。减数分裂期间Mca1细胞分布的分析表明，在减数分裂程序的早期、中期和后期，它与染色体和姐妹染色单体共定位。缺乏Mca1的细胞在低铜条件下减数分裂停滞于中期I。结合研究表明，在大肠杆菌中作为融合蛋白表达的Mca1的N端150个残基片段与mfc1(+)启动子的TCGGCG序列特异性相互作用。综上所述，这些结果确定了顺式调控TCGGCG序列和转录因子Mca1是响应铜饥饿激活减数分裂铜转运mfc1(+)基因的关键成分。
