Roussel M F, Davis J N, Cleveland J L, Ghysdael J, Hiebert S W
Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105.
Oncogene. 1994 Feb;9(2):405-15.
NIH3T3 cells expressing a mutant colony-stimulating factor-1 receptor (CSF-1R) containing a phenylalanine for tyrosine substitution in the tyrosine kinase domain at codon 809 exhibit defective myc regulation and do not enter S phase when stimulated by CSF-1. Enforced expression of either ets-1 or ets-2 in these cells restores their mitogenic response, albeit less efficiently than myc itself, suggesting that ets proteins may regulate c-myc expression. Ets-1 transactivates reporter genes driven by the human and mouse c-myc promoters through the binding site for the transcription factor E2F, the latter being required for E1A- and serum-induced c-myc expression. Analysis of E2F-1 sequences identified a minimal DNA binding domain that is related to those of ets proteins. Although E2F and ets proteins interact with similar consensus DNA binding sites, in vitro binding assays revealed that E2F can bind DNA as a homodimer, whereas ets proteins bind these sites as monomers. E2F and ets proteins do not form heterodimers in vitro and do not transactivate c-myc synergistically. Thus, E2F-1 and ets family members may independently regulate c-myc transcription through the same binding site at different times following growth factor stimulation.
在密码子809的酪氨酸激酶结构域中表达含有苯丙氨酸替代酪氨酸的突变集落刺激因子-1受体（CSF-1R）的NIH3T3细胞，表现出有缺陷的myc调控，并且在受到CSF-1刺激时不会进入S期。在这些细胞中强制表达ets-1或ets-2可恢复它们的促有丝分裂反应，尽管效率低于myc本身，这表明ets蛋白可能调节c-myc表达。Ets-1通过转录因子E2F的结合位点反式激活由人和小鼠c-myc启动子驱动的报告基因，后者是E1A和血清诱导的c-myc表达所必需的。对E2F-1序列的分析确定了一个与ets蛋白的DNA结合结构域相关的最小DNA结合结构域。虽然E2F和ets蛋白与相似的共有DNA结合位点相互作用，但体外结合试验表明，E2F可以作为同二聚体结合DNA，而ets蛋白作为单体结合这些位点。E2F和ets蛋白在体外不形成异二聚体，也不协同反式激活c-myc。因此，E2F-1和ets家族成员可能在生长因子刺激后的不同时间通过相同的结合位点独立调节c-myc转录。
