Parasuraman Prasanna, Mulligan Peter, Walker James A, Li Bihua, Boukhali Myriam, Haas Wilhelm, Bernards Andre
From the Massachusetts General Hospital Center for Cancer Research and Harvard Medical School, Charlestown, Massachusetts 02129.
From the Massachusetts General Hospital Center for Cancer Research and Harvard Medical School, Charlestown, Massachusetts 02129
J Biol Chem. 2017 Feb 17;292(7):2679-2689. doi: 10.1074/jbc.M116.769216. Epub 2016 Dec 22.
The negative regulator of Rho family GTPases, p190A RhoGAP, is one of six mammalian proteins harboring so-called FF motifs. To explore the function of these and other p190A segments, we identified interacting proteins by tandem mass spectrometry. Here we report that endogenous human p190A, but not its 50% identical p190B paralog, associates with all 13 eIF3 subunits and several other translational preinitiation factors. The interaction involves the first FF motif of p190A and the winged helix/PCI domain of eIF3A, is enhanced by serum stimulation and reduced by phosphatase treatment. The p190A/eIF3A interaction is unaffected by mutating phosphorylated p190A-Tyr, but disrupted by a S296A mutation, targeting the only other known phosphorylated residue in the first FF domain. The p190A-eIF3 complex is distinct from eIF3 complexes containing S6K1 or mammalian target of rapamycin (mTOR), and appears to represent an incomplete preinitiation complex lacking several subunits. Based on these findings we propose that p190A may affect protein translation by controlling the assembly of functional preinitiation complexes. Whether such a role helps to explain why, unique among the large family of RhoGAPs, p190A exhibits a significantly increased mutation rate in cancer remains to be determined.
Rho家族GTP酶的负调控因子p190A RhoGAP是六种含有所谓FF基序的哺乳动物蛋白之一。为了探究这些以及其他p190A片段的功能，我们通过串联质谱法鉴定了相互作用蛋白。在此我们报告，内源性人类p190A而非与其有50%同源性的旁系同源蛋白p190B，与所有13个eIF3亚基以及其他几个翻译起始前因子相关联。这种相互作用涉及p190A的第一个FF基序和eIF3A的翼状螺旋/PCI结构域，血清刺激可增强该相互作用，而磷酸酶处理则可减弱这种相互作用。p190A/eIF3A相互作用不受p190A酪氨酸磷酸化突变的影响，但被S296A突变破坏，该突变针对第一个FF结构域中唯一已知的另一个磷酸化残基。p190A - eIF3复合物与含有S6K1或雷帕霉素哺乳动物靶标（mTOR）的eIF3复合物不同，似乎代表一种缺乏几个亚基的不完整起始前复合物。基于这些发现，我们提出p190A可能通过控制功能性起始前复合物的组装来影响蛋白质翻译。这样的作用是否有助于解释为什么在RhoGAP大家族中，p190A在癌症中表现出显著增加的突变率，仍有待确定。
