Regulation mechanism of cell cycle by differentiation signals

DNA复制相关元件结合因子（DREF）被认为参与果蝇DNA复制和增殖相关基因的调控。过表达DREF可诱导果蝇眼内DNA异位合成和细胞凋亡，抑制视细胞分化，使果蝇出现严重的粗糙眼表型。我们使用过表达DREF的果蝇品系作为筛选修饰粗糙眼表型的突变的工具。我们鉴定了20个品系，包括eIF 4a和skpA基因突变，当它们是突变杂合子时，它们抑制和6个品系增强粗糙眼表型。由于报道了eIF 4a蛋白通过调节蛋白翻译与生长相关，因此通过DREF调节eIF 4a基因表达对于调节细胞增殖是重要的。SKPa是果蝇SCF复合物的组分，其与泛素缀合酶UbcDl组合起作用。因此，DREF可以播放 ...更多信息 酵母单杂交筛选使用dPCNA启动子中DRE的三个串联重复序列作为诱饵，允许分离编码Cut的cDNA，Cut是哺乳动物CCAAT-置换蛋白（CDP）/Cux的果蝇同源物。电泳迁移率变动分析表明，削减绑定到两个DRE。在对Cut或DREF进行RNA干扰后，通过果蝇S2细胞中的瞬时荧光素酶表达测定来测量dPCNA启动子活性，表明DREF激活dPCNA启动子，而Cut作为阻遏物起作用。染色质免疫沉淀分析在20-羟基蜕皮激素的存在或不存在下进一步显示DREF和切蛋白定位在基因组区域中含有的dPCNA启动子在S2细胞中，特别是在切的情况下诱导分化。这些结果表明，在分化状态下，Cut通过与启动子区结合而作为dPCNA基因的转录抑制因子发挥作用，而DREF在细胞增殖期间与DRE结合以促进dPCNA的表达。少

The DNA replication-related element-binding factor (DREF) has been suggested to be involved in regulation of DNA replication and proliferation-related genes in Drosophila. Over-expression of DREF induced ectopic DNA synthesis and apoptosis, and inhibited the photoreceptor cell differentiation in eye imaginal discs and adult flies exhibited a severe rough eye phenotype. We used DREF over-expressing fly lines as a tool to screen mutations that modify the rough eye phenotype. We identified 20 lines including eIF4a and skpA gene mutations that suppressed and 6 lines that enhanced the rough eye phenotype when they were heterozygous for the mutations. Since it is reported that eIF4a protein is associated with growth by regulating protein translation, regulation of eIF4a gene expression by DREF would be important for regulation of cell proliferation. SKPa is component of a Drosophila SCF complex that functions in combination with the ubiquitin conjugating enzyme UbcDl. DREF may therefore play … More roles in regulation of protein metabolism at the onset of cell proliferation.A yeast one-hybrid screen using three tandem repeats of DRE in dPCNA promoter as the bait allowed isolation of a cDNA encoding Cut, a Drosophila homologue of mammalian CCAAT-displacement protein (CDP)/Cux. Electrophoretic mobility shift assays showed that Cut bound to both DRE. Measurement of dPCNA promoter activity by.transient luciferase expression assays in Drosophila S2 cells after an RNA interference for Cut or DREF showed DREF activates the dPCNA promoter while Cut functions as a repressor. Chromatin immunoprecipitation assays in the presence or absence of 20-hydroxyecdysone further showed both DREF and Cut proteins to be localized in the genomic region containing the dPCNA promoter in S2 cells, especially in the Cut case upon induction of differentiation. These results indicate that Cut functions as a transcriptional repressor of dPCNA gene by binding to the promoter region in the differentiated state, while DREF binds to DRE to promote expression of dPCNA during cell proliferation. Less