Luo Y, Ullrich R C, Novotny C P
Department of Microbiology and Molecular Genetics, University of Vermont, Burlington 05405.
Mol Gen Genet. 1994 Aug 2;244(3):318-24. doi: 10.1007/BF00285460.
The A alpha mating-type locus is one of four master regulatory loci controlling sexual development in Schizophyllum commune. The A alpha locus contains two homeobox genes, Y and Z, encoding two homeodomain-related proteins, Y and Z. Y and Z are each multiallelic genes. When haploid strains form fusion cells, only particular combinations of Y and Z alleles activate A alpha-regulated sexual development. The role of the putative homeodomain was examined in several Y and Z alleles by site-directed mutagenesis of regions critical to secondary structure and function of homeodomains. Mutations of the Z homeobox do not affect the function of Z proteins in A alpha-activated development, but mutations of Y homeoboxes destroy the ability of Y proteins to activate development. We conclude that only one of two A alpha homeodomain-related regulators relies upon the homeodomain motif to effect gene expression in sexual development. This conclusion affords a refinement of our working hypothesis for the mechanism by which A alpha proteins may regulate target gene expression. On the basis of our results with the Z protein, we speculate that the DNA-binding motifs of some transcriptional regulators may be lost or modified during evolution once these regulators have been recruited to participate in complexes with other DNA-binding proteins.
Aα交配型位点是控制裂褶菌有性发育的四个主要调控位点之一。Aα位点包含两个同源异型框基因Y和Z，它们分别编码两种与同源结构域相关的蛋白质Y和Z。Y和Z均为多等位基因。当单倍体菌株形成融合细胞时，只有Y和Z等位基因的特定组合才能激活Aα调控的有性发育。通过对同源结构域二级结构和功能至关重要的区域进行定点诱变，研究了几个Y和Z等位基因中假定同源结构域的作用。Z同源异型框的突变不影响Z蛋白在Aα激活的发育中的功能，但Y同源异型框的突变会破坏Y蛋白激活发育的能力。我们得出结论，在有性发育中，两个与Aα同源结构域相关的调节因子中只有一个依赖同源结构域基序来影响基因表达。这一结论使我们关于Aα蛋白调控靶基因表达机制的工作假设更加完善。基于我们对Z蛋白的研究结果，我们推测，一旦某些转录调节因子被招募来参与与其他DNA结合蛋白的复合物，它们的DNA结合基序在进化过程中可能会丢失或发生改变。
