Hall M N, Johnson A D
Science. 1987 Aug 28;237(4818):1007-12. doi: 10.1126/science.2887035.
The alpha 2 protein, the product of the MAT alpha 2 gene, is a regulator of cell type in the yeast Saccharomyces cerevisiae. It represses transcription of a group of cell type-specific genes by binding to an operator located upstream of each target gene. Fifteen in-frame deletions within the coding region of the MAT alpha 2 gene were constructed. The deletion alleles were examined for phenotypes conferred in vivo, and the encoded mutant proteins were assayed for ability to bind specifically to the operator in vitro. This analysis has revealed that the sequence-specific DNA-binding domain of alpha 2 is located within a region of 68 amino acids. This region of alpha 2 has significant homology with the homeo domain, a conserved sequence found in the products of several Drosophila homeotic and segmentation genes. In addition, there is a class of mutant alpha 2 proteins that binds tightly and specifically to the operator in vitro, but fails to repress transcription in vivo.
α2蛋白是MATα2基因的产物，是酿酒酵母中细胞类型的调节因子。它通过与位于每个靶基因上游的操纵子结合来抑制一组细胞类型特异性基因的转录。在MATα2基因的编码区内构建了15个读框内缺失。检测缺失等位基因在体内赋予的表型，并检测编码的突变蛋白在体外与操纵子特异性结合的能力。该分析表明，α2的序列特异性DNA结合结构域位于68个氨基酸的区域内。α2的这一区域与同源结构域具有显著的同源性，同源结构域是在几个果蝇同源异型和分节基因的产物中发现的保守序列。此外，有一类突变α2蛋白在体外能紧密且特异性地结合操纵子，但在体内不能抑制转录。
