Lin Yin C, Gralla Jay D
Department of Chemistry and Biochemistry, The Molecular Biology Institute, University of California Los Angeles Los Angeles, CA 90095-1569, USA.
Nucleic Acids Res. 2005 May 25;33(9):3072-81. doi: 10.1093/nar/gki623. Print 2005.
TFIIE and TFIIH are essential for the promoter opening and escape that occurs as RNA polymerase II transits into early elongation. XPB, a subunit of TFIIH, contains an ATP-dependent helicase activity that is used in both of these processes. Here, we show that the smaller beta subunit of TFIIE stimulates the XPB helicase and ATPase activities. The larger alpha subunit can use its known inhibitory activity to moderate the stimulation by the beta subunit. Regions of TFIIE beta required for the helicase stimulation were identified. Mutants were constructed that are defective in stimulating the XPB helicase but still allow intact TFIIE to bind and recruit XPB and TFIIH to form the pre-initiation complex. In a test for the functional significance of the stimulatory effect of TFIIE beta, these mutant forms of TFIIE were shown to be defective in a transcription assay on linear DNA. The data suggest that the beta subunit of TFIIE is an ATPase and helicase co-factor that can assist the XPB subunit of TFIIH during transcription initiation and the transition to early elongation, enhancing the potential diversity of regulatory targets.
TFIIE和TFIIH对于启动子开放以及RNA聚合酶II进入早期延伸阶段时发生的启动子逃逸至关重要。TFIIH的一个亚基XPB具有依赖ATP的解旋酶活性，这两个过程都会用到该活性。在此，我们表明TFIIE较小的β亚基可刺激XPB解旋酶和ATP酶活性。较大的α亚基可利用其已知的抑制活性来调节β亚基的刺激作用。我们确定了刺激解旋酶所需的TFIIEβ区域。构建了在刺激XPB解旋酶方面存在缺陷但仍能使完整的TFIIE结合并募集XPB和TFIIH以形成预起始复合物的突变体。在一项关于TFIIEβ刺激作用功能意义的测试中，这些TFIIE的突变形式在对线性DNA的转录测定中表现出缺陷。数据表明，TFIIE的β亚基是一种ATP酶和解旋酶辅助因子，在转录起始和向早期延伸的转变过程中可协助TFIIH的XPB亚基，增强调控靶点的潜在多样性。
