Zhang Zhiqiang, Gilmour David S
Department of Biochemistry and Molecular Biology, Center for Gene Regulation, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Mol Cell. 2006 Jan 6;21(1):65-74. doi: 10.1016/j.molcel.2005.11.002.
The mechanism by which Pol II terminates transcription in metazoans is not understood. We show that Pcf11 is directly involved in termination in Drosophila. dPcf11 is concentrated at the 3' end of the hsp70 gene in cells, and depletion of dPcf11 with RNAi causes Pol II to readthrough the normal region of termination. dPcf11 also localizes to most transcribed loci on polytene chromosomes. Biochemical analysis reveals that dPcf11 dismantles elongation complexes by a CTD-dependent but nucleotide-independent mechanism and that dPcf11 forms a bridge between the CTD and RNA. This bridge appears to be crucial because an anti-CTD antibody, which also dismantles the elongation complex, is found to bridge the CTD to RNA. dPcf11 was observed to inhibit transcription at low, but not high, nucleotide levels, suggesting that dPcf11 dismantles paused elongation complexes. These results provide a biochemical basis for the dependency of termination on pausing and the CTD in metazoans.
在后生动物中，RNA聚合酶II（Pol II）终止转录的机制尚不清楚。我们发现Pcf11直接参与果蝇中的转录终止过程。在细胞中，果蝇Pcf11（dPcf11）集中在hsp70基因的3'末端，通过RNA干扰耗尽dPcf11会导致Pol II通读正常的终止区域。dPcf11也定位于多线染色体上的大多数转录位点。生化分析表明，dPcf11通过一种依赖于CTD但不依赖于核苷酸的机制拆解延伸复合物，并且dPcf11在CTD和RNA之间形成桥梁。这种桥梁似乎至关重要，因为一种同样能拆解延伸复合物的抗CTD抗体也能将CTD与RNA连接起来。研究观察到dPcf11在低核苷酸水平而非高核苷酸水平下抑制转录，这表明dPcf11拆解了暂停的延伸复合物。这些结果为后生动物中转录终止对暂停和CTD的依赖性提供了生化基础。
