Kettenberger Hubert, Armache Karim-Jean, Cramer Patrick
Institute of Biochemistry, Gene Center, University of Munich, Feodor-Lynen-Str. 25, 81377 Munich, Germany.
Cell. 2003 Aug 8;114(3):347-57. doi: 10.1016/s0092-8674(03)00598-1.
The transcription elongation factor TFIIS induces mRNA cleavage by enhancing the intrinsic nuclease activity of RNA polymerase (Pol) II. We have diffused TFIIS into Pol II crystals and derived a model of the Pol II-TFIIS complex from X-ray diffraction data to 3.8 A resolution. TFIIS extends from the polymerase surface via a pore to the internal active site, spanning a distance of 100 A. Two essential and invariant acidic residues in a TFIIS loop complement the Pol II active site and could position a metal ion and a water molecule for hydrolytic RNA cleavage. TFIIS also induces extensive structural changes in Pol II that would realign nucleic acids in the active center. Our results support the idea that Pol II contains a single tunable active site for RNA polymerization and cleavage, in contrast to DNA polymerases with two separate active sites for DNA polymerization and cleavage.
转录延伸因子TFIIS通过增强RNA聚合酶（Pol）II的内在核酸酶活性来诱导mRNA切割。我们已将TFIIS扩散到Pol II晶体中，并根据X射线衍射数据推导出分辨率为3.8埃的Pol II-TFIIS复合物模型。TFIIS通过一个孔从聚合酶表面延伸至内部活性位点，跨越100埃的距离。TFIIS环中的两个必需且不变的酸性残基与Pol II活性位点互补，可定位一个金属离子和一个水分子用于水解RNA切割。TFIIS还会在Pol II中诱导广泛的结构变化，这会使活性中心的核酸重新排列。我们的结果支持这样一种观点，即与具有两个分别用于DNA聚合和切割的活性位点的DNA聚合酶不同，Pol II含有一个用于RNA聚合和切割的单一可调活性位点。
