Lu C C, Yen T S
Department of Pathology, University of California School of Medicine, San Francisco, USA.
Virology. 1996 Nov 15;225(2):387-94. doi: 10.1006/viro.1996.0613.
The middle and small surface proteins of hepatitis B virus are translated from 5'-heterogeneous transcripts specified by the S promoter. We have generated a series of linker-substitution mutants that encompass the 130 base pairs comprising this promoter and measured the amount of transcripts and protein products synthesized from each mutant. The results confirm our previous finding that a CCAAT element is an important up-stream activating element for this promoter, as mutation of this element leads to a >20-fold decrease in promoter activity. In vitro binding assays showed that the cellular transcription factor NF-Y (CCAAT-binding factor) binds to this element, and expression of a dominant-negative NF-Y subunit in transfected cells specifically reduced surface protein expression from the S promoter via the CCAAT element. In addition, two Sp1 sites also contribute to S promoter activity by a total of approximately 6-fold. Therefore, the S promoter is activated by both NF-Y and Sp1, but more strongly by the former factor.
乙型肝炎病毒的中、小表面蛋白由S启动子指定的5'-异质转录本翻译而来。我们构建了一系列包含该启动子的130个碱基对的接头取代突变体，并测量了每个突变体合成的转录本和蛋白质产物的量。结果证实了我们之前的发现，即CCAAT元件是该启动子的一个重要上游激活元件，因为该元件的突变导致启动子活性下降>20倍。体外结合试验表明，细胞转录因子NF-Y（CCAAT结合因子）与该元件结合，并且在转染细胞中显性负性NF-Y亚基的表达通过CCAAT元件特异性降低了S启动子的表面蛋白表达。此外，两个Sp1位点对S启动子活性的贡献总计约为6倍。因此，S启动子由NF-Y和Sp1共同激活，但前者的激活作用更强。
