Grossel M J, Barsoum J, Prakash S S, Androphy E J
Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Virology. 1996 Mar 1;217(1):301-10. doi: 10.1006/viro.1996.0117.
The papillomavirus E2 protein contains an amino-terminal region thought necessary and sufficient to support transcriptional activation and a carboxy-terminal region shown to direct sequence-specific DNA binding and dimerization. A cysteine residue in the center of the E2 DNA recognition helix is highly conserved among papillomavirus E2 proteins. Mutations of this cysteine in bovine papillomavirus type 1 E2 to serine and glycine resulted in proteins which failed to activate E2-dependent promoters in mammalian cells. These E2 mutants were DNA-binding competent, dimeric, and nuclear. When fused to the VP16 transactivation domain, C-terminal regions of E2 containing the mutations at 340 supported transcriptional activation, indicating that the heterologous trans-activation domain did not require cysteine in the DNA-binding helix as did the full-length E2 transactivating protein. Although cysteine-340 was required for transcriptional activation it was not required for DNA replication in vivo. Together, these results suggest that the E2 DNA-binding domain may directly contribute to functions of transcriptional activation previously thought limited to the N-terminal domain.
乳头瘤病毒E2蛋白包含一个氨基末端区域，该区域被认为是支持转录激活所必需且足够的，以及一个羧基末端区域，该区域被证明可指导序列特异性DNA结合和二聚化。E2 DNA识别螺旋中心的一个半胱氨酸残基在乳头瘤病毒E2蛋白中高度保守。将牛乳头瘤病毒1型E2中的这个半胱氨酸突变为丝氨酸和甘氨酸后产生的蛋白质无法在哺乳动物细胞中激活E2依赖的启动子。这些E2突变体具有DNA结合能力、二聚体形式且定位于细胞核。当与VP16反式激活结构域融合时，E2的羧基末端区域在340处含有突变，可支持转录激活，这表明异源反式激活结构域不像全长E2反式激活蛋白那样在DNA结合螺旋中需要半胱氨酸。虽然半胱氨酸340是转录激活所必需的，但在体内DNA复制过程中并非必需。总之，这些结果表明E2 DNA结合结构域可能直接有助于此前认为仅限于氨基末端结构域的转录激活功能。
