Skeiky Y A, Iatrou K
Department of Medical Biochemistry, University of Calgary, Alberta, Canada.
Mol Cell Biol. 1991 Apr;11(4):1954-64. doi: 10.1128/mcb.11.4.1954-1964.1991.
Two DNA-binding proteins, BCFI and BCFII, that interact with defined promoter sequences of silkmoth chorion genes of late developmental specificity appear in the nuclei of follicular cells at a time that coincides with the transcriptional activation of the corresponding genes. BCFI prebinding is shown to be indispensable for stable binding of BCFII to its cognate sequence. BCFI and BCFII synergism requires a relatively stringent stereospecific alignment and is a prerequisite for the assembly of higher-order protein-promoter DNA complexes containing additional factors, which are neither gene (stage) nor class (chorion) specific. Binding of BCFI to its site correlates with the induction of DNA structural perturbations that may facilitate assembly of additional factors on the promoter. The BCFI-binding domain contains a core hexanucleotide sequence, AGATAA, which represents the major binding determinant of the erythroid-specific transcription factor GATA-1 of higher vertebrates. This sequence is shown to be necessary and sufficient for binding of BCFI, as it is for a factor that is present in induced K562 human erythroleukemic cells, presumably GATA-1. Comparative analyses of mobility shift patterns obtained with partially proteolyzed preparations of these two unrelated factors were used to confirm that a BCFI-like chorion promoter-binding protein, which is present in the nuclei of an established silkmoth cell line derived from ovarian tissue, is in fact BCFI. The transcriptional repression of endogenous chorion genes in this cell line coupled with the documented absence of factor BCFII suggests that the synergistic interactions between these two factors constitute a minimum requirement for late chorion gene expression.
两种与家蚕晚期发育特异性绒毛膜基因特定启动子序列相互作用的DNA结合蛋白BCFI和BCFII，在与相应基因转录激活同时出现于滤泡细胞核中。已表明BCFI预结合对于BCFII与其同源序列的稳定结合是必不可少的。BCFI和BCFII协同作用需要相对严格的立体特异性排列，并且是包含其他既非基因（阶段）特异性也非类别（绒毛膜）特异性因子的高阶蛋白质-启动子DNA复合物组装的先决条件。BCFI与其位点的结合与DNA结构扰动的诱导相关，这可能有助于在启动子上组装其他因子。BCFI结合域包含一个核心六核苷酸序列AGATAA，它代表高等脊椎动物红系特异性转录因子GATA-1的主要结合决定因素。该序列对于BCFI的结合是必要且充分的，就如同对于诱导的K562人红白血病细胞中存在的一种因子（可能是GATA-1）一样。通过对这两种不相关因子的部分蛋白酶解制剂获得的迁移率变动模式进行比较分析，以确认存在于源自卵巢组织的已建立家蚕细胞系细胞核中的一种类似BCFI的绒毛膜启动子结合蛋白实际上就是BCFI。该细胞系中内源性绒毛膜基因的转录抑制以及已记录的BCFII因子缺失表明，这两种因子之间的协同相互作用构成了晚期绒毛膜基因表达的最低要求。
