Schimanski Bernd, Brandenburg Jens, Nguyen Tu Ngoc, Caimano Melissa Jo, Günzl Arthur
Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, CT 06030, USA.
Nucleic Acids Res. 2006 Mar 22;34(6):1676-84. doi: 10.1093/nar/gkl090. Print 2006.
The lack of general class II transcription factors was a hallmark of the genomic sequences of the human parasites Trypanosoma brucei, Trypanosoma cruzi and Leishmania major. However, the recent identification of TFIIA as part of a protein complex essential for RNA polymerase II-mediated transcription of SLRNA genes, which encode the trans splicing-specific spliced leader RNA, suggests that trypanosomatids assemble a highly divergent set of these factors at the SLRNA promoter. Here we report the identification of a trypanosomatid TFIIB-like (TFIIB(like)) protein which has limited overall sequence homology to eukaryotic TFIIB and archaeal TFB but harbors conserved residues within the N-terminal zinc ribbon domain, the B finger and cyclin repeat I. In accordance with the function of TFIIB, T.brucei TFIIB(like) is encoded by an essential gene, localizes to the nucleus, specifically binds to the SLRNA promoter, interacts with RNA polymerase II, and is absolutely required for SLRNA transcription.
缺乏通用的II类转录因子是人类寄生虫布氏锥虫、克氏锥虫和硕大利什曼原虫基因组序列的一个特征。然而，最近发现TFIIA是RNA聚合酶II介导的SLRNA基因转录所必需的蛋白质复合物的一部分，这些基因编码反式剪接特异性剪接前导RNA，这表明锥虫在SLRNA启动子处组装了一组高度不同的这些因子。在这里，我们报告鉴定了一种锥虫TFIIB样（TFIIB(like)）蛋白，它与真核TFIIB和古细菌TFB的整体序列同源性有限，但在N端锌带结构域、B指和细胞周期蛋白重复序列I内含有保守残基。根据TFIIB的功能，布氏锥虫TFIIB(like)由一个必需基因编码，定位于细胞核，特异性结合SLRNA启动子，与RNA聚合酶II相互作用，并且是SLRNA转录绝对必需的。
