植物特有的TFIIB相关蛋白pBrp是RNA聚合酶I的一种通用转录因子。
The plant-specific TFIIB-related protein, pBrp, is a general transcription factor for RNA polymerase I.
作者信息
Imamura Sousuke, Hanaoka Mitsumasa, Tanaka Kan
机构信息
Institute of Molecular and Cellular Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
出版信息
EMBO J. 2008 Sep 3;27(17):2317-27. doi: 10.1038/emboj.2008.151.
TFIIB and BRF are general transcription factors (GTFs) for eukaryotic RNA polymerases II and III, respectively, and have important functions in transcriptional initiation. In this study, the third type of TFIIB-related protein, pBrp, found in plant lineages was characterized in the red alga Cyanidioschyzon merolae. Chromatin immunoprecipitation analysis revealed that CmpBrp specifically occupied the rDNA promoter region in vivo, and the occupancy was proportional to de novo 18S rRNA synthesis. Consistently, CmpBrp and CmTBP cooperatively bound the rDNA promoter region in vitro, and the binding site was identified at a proximal downstream region of the transcription start point. alpha-Amanitin-resistant transcription from the rDNA promoter in crude cell lysate was severely inhibited by the CmpBrp antibody and was also inhibited when DNA template with a mutated CmpBrp-CmTBP binding site was used. CmpBrp was shown to co-immunoprecipitate and co-localize with the RNA polymerase I subunit, CmRPA190, in the cell. Thus, together with comparative studies of Arabidopsis pBrp, we concluded that pBrp is a GTF for RNA polymerase I in plant cells.
TFIIB和BRF分别是真核生物RNA聚合酶II和III的通用转录因子（GTF），在转录起始中具有重要功能。在本研究中，在红藻梅氏嗜热栖热菌中对植物谱系中发现的第三种TFIIB相关蛋白pBrp进行了表征。染色质免疫沉淀分析表明，CmpBrp在体内特异性占据rDNA启动子区域，且占据程度与从头合成18S rRNA成正比。一致地，CmpBrp和CmTBP在体外协同结合rDNA启动子区域，并且在转录起始点近端下游区域鉴定到了结合位点。粗细胞裂解物中rDNA启动子的α-鹅膏蕈碱抗性转录受到CmpBrp抗体的严重抑制，并且当使用具有突变的CmpBrp-CmTBP结合位点的DNA模板时也受到抑制。结果表明，CmpBrp在细胞中与RNA聚合酶I亚基CmRPA190共免疫沉淀并共定位。因此，并结合对拟南芥pBrp的比较研究，我们得出结论，pBrp是植物细胞中RNA聚合酶I的GTF。
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