The transformation suppressor Pdcd4 is a novel eukaryotic translation initiation factor 4A binding protein that inhibits translation
The transformation suppressor Pdcd4 is a novel eukaryotic translation initiation factor 4A binding protein that inhibits translation
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DOI：
10.1128/mcb.23.1.26-37.2003
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发表时间：
2003-01-01
影响因子：
5.3
通讯作者：
Colburn, NH
中科院分区：
文献类型：
--
作者：
Yang, HS;Jansen, AP;Colburn, NH
Pdcd 4是一种新型的转化抑制因子，可抑制肿瘤启动子诱导的肿瘤转化和转化所需的AP-1依赖性转录的激活。酵母双杂交分析显示Pdcd 4与真核生物翻译起始因子eIF 4AI和eIF 4AII相关。免疫荧光共聚焦显微镜显示Pdcd 4与eIF 4A共定位于细胞质中。eIF 4A是一种ATP依赖性RNA解旋酶，需要解旋5' mRNA二级结构。重组Pdcd 4特异性抑制eIF 4A和eIF 4F的解旋酶活性。体内翻译试验表明，Pdcd 4抑制帽依赖性，但不内部核糖体进入位点（IRES）依赖性翻译。相反，Pdcd 4（D418 A），一种与eIF 4A结合失活的突变体，未能抑制帽依赖性或IRES依赖性翻译或AP-1反式激活。重组Pdcd 4阻止eIF 4A与eIF 4G的C-末端区域（氨基酸1040至1560）结合，但不与eIF 4G的中间区域（氨基酸635至1039）结合。此外，Pdcd 4和Pdcd 4（D418 A）都结合到eIF 4G的中间区域。因此，Pdcd 4抑制翻译的机制似乎涉及抑制eIF 4A解旋酶，干扰eIF 4A与eIF 4G的结合-解离，以及抑制eIF 4A与eIF 4G的C-末端结构域的结合。Pdcd 4与eIF 4A的结合与其转化抑制活性有关，因为Pdcd 4-eIF 4A结合和随后的翻译抑制是Pdcd 4反式抑制AP-1所必需的。
Pdcd4 is a novel transformation suppressor that inhibits tumor promoter-induced neoplastic transformation and the activation of AP-1-dependent transcription required for transformation. A yeast two-hybrid analysis revealed that Pdcd4 associates with the eukaryotic translation initiation factors eIF4AI and eIF4AII. Immunofluorescent confocal microscopy showed that Pdcd4 colocalizes with eIF4A in the cytoplasm. eIF4A is an ATP-dependent RNA helicase needed to unwind 5' mRNA secondary structure. Recombinant Pdcd4 specifically inhibited the helicase activity of eIF4A and eIF4F. In vivo translation assays showed that Pdcd4 inhibited cap-dependent but not internal ribosome entry site (IRES)-dependent translation. In contrast, Pdcd4(D418A), a mutant inactivated for binding to eIF4A, failed to inhibit cap-dependent or IRES-dependent translation or AP-1 transactivation. Recombinant Pdcd4 prevented eIF4A from binding to the C-terminal region of eIF4G (amino acids 1040 to 1560) but not to the middle region of eIF4G(amino acids 635 to 1039). In addition, both Pdcd4 and Pdcd4(D418A) bound to the middle region of eIF4G. The mechanism by which Pdcd4 inhibits translation thus appears to involve inhibition of eIF4A helicase, interference with eIF4A association-dissociation from eIF4G, and inhibition of eIF4A binding to the C-terminal domain of eIF4G. Pdcd4 binding to eIF4A is linked to its transformation-suppressing activity, as Pdcd4-eIF4A binding and consequent inhibition of translation are required for Pdcd4 transrepression of AP-1.