Cdc73 Subunit of Paf1 Complex Contains C-terminal Ras-like Domain That Promotes Association of Paf1 Complex with Chromatin
Cdc73 Subunit of Paf1 Complex Contains C-terminal Ras-like Domain That Promotes Association of Paf1 Complex with Chromatin
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DOI：
10.1074/jbc.m111.325647
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发表时间：
2012-03-30
影响因子：
4.8
通讯作者：
VanDemark, Andrew P.
中科院分区：
文献类型：
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作者：
Amrich, Christopher G.;Davis, Christopher P.;VanDemark, Andrew P.
保守的Paf1复合物定位于基因的编码区，并促进转录延伸过程中的多个过程，包括组蛋白修饰的调节。然而，Paf1复合物募集到活性基因的机制尚不清楚。在这里，我们描述了一个以前未被识别的结构域内的Cdc73亚基的Paf1复合物，Cdc73 C-结构域，并证明其重要性Paf1复合物占用转录染色质。C结构域的缺失导致与延伸缺陷相关的表型，而没有明显的复合物完整性损失。同时突变的C-结构域和另一个亚基的Paf1复合物，Rtf1，会导致增强的突变体表型和组蛋白H3赖氨酸36三甲基化的损失。C-结构域的晶体结构揭示了与小GTP酶的Ras家族的意想不到的相似性。取代深核苷酸结合口袋，C-结构域包含高度保守残基的大但相对平坦的表面，没有配体。C结构域的缺失导致多个Paf1复合物亚基的染色质缔合减少。我们得出结论，Cdc73 C-结构域可能构成一个蛋白质相互作用的表面，其功能与Rtf1在耦合的Paf1复合物的RNA聚合酶II的延伸机械。
The conserved Paf1 complex localizes to the coding regions of genes and facilitates multiple processes during transcription elongation, including the regulation of histone modifications. However, the mechanisms that govern Paf1 complex recruitment to active genes are undefined. Here we describe a previously unrecognized domain within the Cdc73 subunit of the Paf1 complex, the Cdc73 C-domain, and demonstrate its importance for Paf1 complex occupancy on transcribed chromatin. Deletion of the C-domain causes phenotypes associated with elongation defects without an apparent loss of complex integrity. Simultaneous mutation of the C-domain and another subunit of the Paf1 complex, Rtf1, causes enhanced mutant phenotypes and loss of histone H3 lysine 36 trimethylation. The crystal structure of the C-domain reveals unexpected similarity to the Ras family of small GTPases. Instead of a deep nucleotide-binding pocket, the C-domain contains a large but comparatively flat surface of highly conserved residues, devoid of ligand. Deletion of the C-domain results in reduced chromatin association for multiple Paf1 complex subunits. We conclude that the Cdc73 C-domain probably constitutes a protein interaction surface that functions with Rtf1 in coupling the Paf1 complex to the RNA polymerase II elongation machinery.