Kugler W, Kaling M, Ross K, Wagner U, Ryffel G U
Kernforschungszentrum Karlsruhe, Institut für Genetik und Toxikologie, Karlsruhe, FRG.
Nucleic Acids Res. 1990 Dec 11;18(23):6943-51. doi: 10.1093/nar/18.23.6943.
The vitellogenin genes of Xenopus are liver-specifically expressed. An in vitro transcription system derived from rat liver nuclei allowed us to define the cis-element BABS (B-activator binding site) in the promoter of the B1 vitellogenin gene. An oligonucleotide encompassing the region from -53 to -44 linked to a TATA box is sufficient for a tenfold increase of the transcriptional activity. Gel retardation assays with nuclear rat liver proteins reveal two DNA-protein complexes: Complex 1 can be competed by the USF/MLTF binding site of the adeno major late promoter whereas complex 2 is a distinct protein we refer to as BAP (B-activator protein). In vitro transcription experiments in the presence of USF/MLTF binding site as competitor show that BAP is an efficient transcription factor. Based on UV cross-linking we estimate that BAP has a molecular weight of 58 kd. Phosphatase treatment reveals that DNA binding of BAP requires phosphorylation. BABS is also present in the hepatitis B virus enhancer suggesting that it might play a role in the tumorigenic potential of the virus.
非洲爪蟾的卵黄蛋白原基因在肝脏中特异性表达。源自大鼠肝细胞核的体外转录系统使我们能够确定B1卵黄蛋白原基因启动子中的顺式元件BABS（B激活剂结合位点）。一个包含从-53到-44区域并与TATA盒相连的寡核苷酸足以使转录活性提高十倍。用大鼠肝细胞核蛋白进行的凝胶阻滞分析揭示了两种DNA-蛋白质复合物：复合物1可被腺病毒主要晚期启动子的USF/MLTF结合位点竞争，而复合物2是一种独特的蛋白质，我们称之为BAP（B激活剂蛋白）。在存在USF/MLTF结合位点作为竞争者的情况下进行的体外转录实验表明，BAP是一种有效的转录因子。基于紫外线交联，我们估计BAP的分子量为58 kd。磷酸酶处理表明BAP的DNA结合需要磷酸化。BABS也存在于乙肝病毒增强子中，这表明它可能在病毒的致瘤潜力中发挥作用。
