Aso T, Lane W S, Conaway J W, Conaway R C
Program in Molecular and Cell Biology, Oklahoma Medical Research Foundation, Oklahoma City 73104, USA.
Science. 1995 Sep 8;269(5229):1439-43. doi: 10.1126/science.7660129.
The Elongin (SIII) complex activates elongation by mammalian RNA polymerase II by suppressing transient pausing of the polymerase at many sites within transcription units. Elongin is a heterotrimer composed of A, B, and C subunits of 110, 18, and 15 kilodaltons, respectively. Here, the mammalian Elongin A gene was isolated and expressed, and the Elongin (SIII) complex reconstituted with recombinant subunits. Elongin A is shown to function as the transcriptionally active component of Elongin (SIII) and Elongin B and C as regulatory subunits. Whereas Elongin C assembles with Elongin A to form an AC complex with increased specific activity, Elongin B, a member of the ubiquitin-homology gene family, appears to serve a chaperone-like function, facilitating assembly and enhancing stability of the Elongin (SIII) complex.
延伸蛋白（SIII）复合物通过抑制聚合酶在转录单位内多个位点的短暂停顿来激活哺乳动物RNA聚合酶II的延伸过程。延伸蛋白是一种异源三聚体，分别由分子量为110、18和15千道尔顿的A、B和C亚基组成。在此，分离并表达了哺乳动物延伸蛋白A基因，并用重组亚基重建了延伸蛋白（SIII）复合物。结果表明，延伸蛋白A作为延伸蛋白（SIII）的转录活性成分发挥作用，而延伸蛋白B和C则作为调节亚基。延伸蛋白C与延伸蛋白A组装形成具有更高比活性的AC复合物，泛素同源基因家族成员延伸蛋白B似乎起到类似伴侣蛋白的作用，促进延伸蛋白（SIII）复合物的组装并增强其稳定性。
