Wang L H, Ing N H, Tsai S Y, O'Malley B W, Tsai M J
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030.
Gene Expr. 1991;1(3):207-16.
The chicken ovalbumin upstream promoter transcription factors (COUP-TFs) are members of the steroid/thyroid hormone receptor superfamily and function in transcriptional regulation of a wide variety of genes. The COUP-TFs purified from HeLa nuclear extract by COUP-affinity chromatography are composed of multiple M(r) forms. The Low M(r) COUP-TFs (43,000, 44,000, 46,000, and 47,000 M(r)) produce a relatively fast migrating complex (C1) with DNA in electrophoresis mobility shift assays, while the high M(r) forms (66,000, 68,000, 72,000, and 74,000 M(r)) produce a slower migrating (C2) complex. The high M(r) COUP-TFs were purified by gel filtration chromatography and independently formed the C2 DNA complex, probably acting as dimers. The high M(r) forms are indistinguishable from the low M(r) COUP-TFs in DNA binding and in enhancement of in vitro transcription from the ovalbumin promoter. The finding of multiple COUP-TF forms led us to clone a second low M(r) COUP-TF, "COUP-TF2." The COUP-TF2 sequence has very strong homology with COUP-TF1. The N-termini of COUP-TF1 and COUP-TF2 are least similar, but both contain glutamine-rich and proline-rich motifs, putative activation domains.
鸡卵清蛋白上游启动子转录因子（COUP-TFs）是类固醇/甲状腺激素受体超家族的成员，在多种基因的转录调控中发挥作用。通过COUP亲和层析从HeLa细胞核提取物中纯化得到的COUP-TFs由多种分子量（M(r)）形式组成。在电泳迁移率变动分析中，低分子量（M(r)）的COUP-TFs（43,000、44,000、46,000和47,000 M(r)）与DNA形成相对迁移较快的复合物（C1），而高分子量（M(r)）形式（66,000、68,000、72,000和74,000 M(r)）则形成迁移较慢的（C2）复合物。高分子量（M(r)）的COUP-TFs通过凝胶过滤层析纯化，并独立形成C2 DNA复合物，可能以二聚体形式发挥作用。高分子量（M(r)）形式在DNA结合和卵清蛋白启动子体外转录增强方面与低分子量（M(r)）的COUP-TFs没有区别。多种COUP-TF形式的发现促使我们克隆了第二个低分子量（M(r)）的COUP-TF，即“COUP-TF2”。COUP-TF2序列与COUP-TF1具有很强的同源性。COUP-TF1和COUP-TF2的N末端相似度最低，但两者都含有富含谷氨酰胺和富含脯氨酸的基序，即推定的激活域。
