The C-Terminal Region of Eukaryotic Translation Initiation Factor 3a (eIF3a) Promotes mRNA Recruitment, Scanning, and, Together with eIF3j and the eIF3b RNA Recognition Motif, Selection of AUG Start Codons
The C-Terminal Region of Eukaryotic Translation Initiation Factor 3a (eIF3a) Promotes mRNA Recruitment, Scanning, and, Together with eIF3j and the eIF3b RNA Recognition Motif, Selection of AUG Start Codons
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DOI：
10.1128/mcb.00280-10
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发表时间：
2010-09-15
影响因子：
5.3
通讯作者：
Hinnebusch, Alan G.
中科院分区：
文献类型：
--
作者：
Chiu, Wen-Ling;Wagner, Susan;Hinnebusch, Alan G.
芽殖酵母真核细胞翻译起始因子3(EIF3)a/Tif32亚基的C末端结构域(CTD)与eIF3亚基j/Hcr1和b/Prt1相互作用，并能结合18S rRNA的螺旋16至18，提示接近40S亚基的mRNA进入通道。我们已经发现保守的Lys-Glu-Arg-Arg(Kerr)基序和a/Tif32CTD附近box6元件的残基发生了替换，这些替换损害了43S预起始复合体(PIC)对mRNA的招募，并提供了扫描和启动密码子识别缺陷的表型。为了与a/Tif32结合并减轻这些a/Tif32突变体的生长缺陷，需要j/Hcr1的正常可有可无的CTD，这表明这两个结构域之间存在物理和功能上的相互作用。A/Tif32 CTD和j/Hcr1 N-末端结构域(NTD)也与b/Prt1的RNA识别基序(RRM)相互作用，而这两个亚基的突变破坏了它们与RRM的相互作用，增加了AUG密码子的泄漏扫描。这些结果以及我们的证据表明，a/Tif32的极端CTD与Rps2和RPS3结合，这导致我们认为a/Tif32CTD直接稳定43S亚单位-mRNA的相互作用，而b/Prt1-RRM-j/Hcr1-a/Tif32-CTD模块结合在mRNA进入通道附近，并调节PIC的扫描有利构象和启动能力构象之间的转换。
The C-terminal domain (CTD) of the a/Tif32 subunit of budding yeast eukaryotic translation initiation factor 3 (eIF3) interacts with eIF3 subunits j/Hcr1 and b/Prt1 and can bind helices 16 to 18 of 18S rRNA, suggesting proximity to the mRNA entry channel of the 40S subunit. We have identified substitutions in the conserved Lys-Glu-Arg-Arg (KERR) motif and in residues of the nearby box6 element of the a/Tif32 CTD that impair mRNA recruitment by 43S preinitiation complexes (PICs) and confer phenotypes indicating defects in scanning and start codon recognition. The normally dispensable CTD of j/Hcr1 is required for its binding to a/Tif32 and to mitigate the growth defects of these a/Tif32 mutants, indicating physical and functional interactions between these two domains. The a/Tif32 CTD and the j/Hcr1 N-terminal domain (NTD) also interact with the RNA recognition motif (RRM) in b/Prt1, and mutations in both subunits that disrupt their interactions with the RRM increase leaky scanning of an AUG codon. These results, and our demonstration that the extreme CTD of a/Tif32 binds to Rps2 and Rps3, lead us to propose that the a/Tif32 CTD directly stabilizes 43S subunit-mRNA interaction and that the b/Prt1-RRM-j/Hcr1-a/Tif32-CTD module binds near the mRNA entry channel and regulates the transition between scanning-conducive and initiation-competent conformations of the PIC.