Simon J, Bornemann D, Lunde K, Schwartz C
Department of Biochemistry, University of Minnesota, St. Paul 55108, USA.
Mech Dev. 1995 Oct;53(2):197-208. doi: 10.1016/0925-4773(95)00434-3.
The extra sex combs (esc) gene product is a transcriptional repressor of homeotic genes. Although it is classified in the Polycomb group (PcG) on the basis of phenotypic criteria, it is distinct from most other PcG repressors in its time of action during development. We describe the temporal profile of esc mRNA expression during embryogenesis and the stage-specific rescue of esc mutants with a heat shock-inducible esc cDNA transformation construct. Both experiments support the idea that esc product plays an early, transient role in repression of homeotic genes. We also present the sequence of a full-length esc cDNA. The predicted esc protein is composed primarily of multiple copies of a repeat motif, termed the WD40 repeat, which are likely used in protein-protein contact. We provide evidence that individual copies of the esc WD40 repeats are needed for function in vivo. We suggest that esc protein is an adaptor that binds to multiple protein partners and assists in the assembly or targeting of other PcG proteins.
额外性梳（esc）基因产物是同源异型基因的转录抑制因子。尽管根据表型标准它被归类于多梳蛋白组（PcG），但在发育过程中其作用时间与大多数其他PcG抑制因子不同。我们描述了胚胎发育过程中esc mRNA表达的时间概况，以及利用热休克诱导的esc cDNA转化构建体对esc突变体进行阶段特异性拯救的情况。这两个实验都支持esc产物在同源异型基因抑制中发挥早期短暂作用的观点。我们还展示了全长esc cDNA的序列。预测的esc蛋白主要由一种重复基序的多个拷贝组成，这种重复基序称为WD40重复，可能用于蛋白质 - 蛋白质相互作用。我们提供证据表明esc的WD40重复的单个拷贝在体内发挥功能是必需的。我们认为esc蛋白是一种衔接子，它与多个蛋白质伙伴结合，并协助其他PcG蛋白的组装或靶向。
