转录因子TFIIB在体内的激活特异性作用。
An activation-specific role for transcription factor TFIIB in vivo.
作者信息
Wu W H, Hampsey M
机构信息
Department of Biochemistry, Division of Nucleic Acids Enzymology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854-5635, USA.
出版信息
Proc Natl Acad Sci U S A. 1999 Mar 16;96(6):2764-9. doi: 10.1073/pnas.96.6.2764.
A yeast mutant was isolated encoding a single amino acid substitution [serine-53 --> proline (S53P)] in transcription factor TFIIB that impairs activation of the PHO5 gene in response to phosphate starvation. This effect is activation-specific because S53P did not affect the uninduced level of PHO5 expression, yet is not specific to PHO5 because Adr1-mediated activation of the ADH2 gene also was impaired by S53P. Pho4, the principal activator of PHO5, directly interacted with TFIIB in vitro, and this interaction was impaired by the S53P replacement. Furthermore, Pho4 induced a conformational change in TFIIB, detected by enhanced sensitivity to V8 protease. The S53P replacement also impaired activation of a lexA(op)-lacZ reporter by a LexA fusion protein to the activation domain of Adr1, thereby indicating that the transcriptional effect on ADH2 expression is specific to the activation function of Adr1. These results define an activation-specific role for TFIIB in vivo and suggest that certain activators induce a conformational change in TFIIB as part of their mechanism of transcriptional stimulation.
分离出一种酵母突变体，其编码的转录因子TFIIB中有一个单氨基酸替换[丝氨酸-53→脯氨酸（S53P）]，该替换会损害PHO5基因在磷酸盐饥饿应答中的激活。这种效应具有激活特异性，因为S53P不影响PHO5基因未诱导时的表达水平，但它并非PHO5所特有的，因为Adr1介导的ADH2基因激活也受到S53P的损害。PHO5的主要激活因子Pho4在体外与TFIIB直接相互作用，并且这种相互作用因S53P替换而受损。此外，Pho4诱导了TFIIB的构象变化，这可通过对V8蛋白酶的敏感性增强来检测。S53P替换还损害了LexA融合蛋白（与Adr1激活结构域融合）对lexA(op)-lacZ报告基因的激活，从而表明对ADH2表达的转录效应是Adr1激活功能所特有的。这些结果确定了TFIIB在体内的激活特异性作用，并表明某些激活因子会诱导TFIIB的构象变化，作为其转录刺激机制的一部分。
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