Jeon C, Yoon H, Agarwal K
Department of Biochemistry, University of Chicago, IL 60637.
Proc Natl Acad Sci U S A. 1994 Sep 13;91(19):9106-10. doi: 10.1073/pnas.91.19.9106.
The eukaryotic transcription factor TFIIS enhances elongation and nascent transcript cleavage activities of RNA polymerase II in a stalled elongation complex. By site-directed mutagenesis, we have demonstrated that invariant residues Asp-261 and Glu-262 of the nucleic acid-binding TFIIS Zn ribbon are critical for stimulation of both elongation and RNA cleavage activities of RNA polymerase II. Substitution of either of these residues inactivates both TFIIS functions, suggesting a related role in both activities. These acidic residues may participate in phosphoryl transfer reactions by a two-metal-ion mechanism in a manner analogous to Klenow fragment. The RNA polymerase II itself may contain a Zn ribbon, in as much as the polymerase's 15-kDa subunit contains a sequence that aligns well with the TFIIS Zn ribbon sequence, including a similarly placed pair of acidic residues.
真核转录因子TFIIS可增强停滞延伸复合物中RNA聚合酶II的延伸和新生转录本切割活性。通过定点诱变，我们已证明核酸结合型TFIIS锌带的不变残基Asp-261和Glu-262对于刺激RNA聚合酶II的延伸和RNA切割活性至关重要。替换这些残基中的任何一个都会使TFIIS的两种功能失活，表明它们在这两种活性中发挥相关作用。这些酸性残基可能通过双金属离子机制参与磷酸转移反应，其方式类似于Klenow片段。RNA聚合酶II本身可能含有一个锌带，因为该聚合酶的15 kDa亚基包含一个与TFIIS锌带序列排列良好的序列，包括一对位置相似的酸性残基。
