Bonnal Sophie, Pileur Frédéric, Orsini Cécile, Parker Fabienne, Pujol Françoise, Prats Anne-Catherine, Vagner Stéphan
INSERM U589, Institut Louis Bugnard, Hopital Rangueil, TSA 50032, 31059 Toulouse Cedex 9, France.
J Biol Chem. 2005 Feb 11;280(6):4144-53. doi: 10.1074/jbc.M411492200. Epub 2004 Nov 3.
Alternative initiation of translation of the human fibroblast growth factor 2 (FGF-2) mRNA at five in-frame CUG or AUG translation initiation codons requires various RNA cis-acting elements, including an internal ribosome entry site (IRES). Here we describe the purification of a trans-acting factor controlling FGF-2 mRNA translation achieved by several biochemical purification approaches. We have identified the heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) as a factor that binds to the FGF-2 5'-leader RNA and that also complements defective FGF-2 translation in vitro in rabbit reticulocyte lysate. Recombinant hnRNP A1 stimulates in vitro translation at the four IRES-dependent initiation codons but has no effect on the cap-dependent initiation codon. Consistent with a role of hnRNP A1 in the control of alternative initiation of translation, short interfering RNA-mediated knock down of hnRNP A1 specifically inhibits translation at the four IRES-dependent initiation codons. Furthermore, hnRNP A1 binds to the FGF-2 IRES, implicating this interaction in the control of alternative initiation of translation.
人成纤维细胞生长因子2（FGF-2）mRNA在五个框内CUG或AUG翻译起始密码子处的选择性翻译起始需要多种RNA顺式作用元件，包括一个内部核糖体进入位点（IRES）。在此，我们描述了通过几种生化纯化方法实现的对控制FGF-2 mRNA翻译的反式作用因子的纯化。我们已鉴定出异质性核核糖核蛋白A1（hnRNP A1）是一种与FGF-2 5'-前导RNA结合的因子，并且在体外兔网织红细胞裂解物中也能补充有缺陷的FGF-2翻译。重组hnRNP A1可刺激四个依赖IRES的起始密码子处的体外翻译，但对依赖帽结构的起始密码子没有影响。与hnRNP A1在选择性翻译起始控制中的作用一致，小干扰RNA介导的hnRNP A1敲低特异性抑制四个依赖IRES的起始密码子处的翻译。此外，hnRNP A1与FGF-2 IRES结合，表明这种相互作用参与了选择性翻译起始的控制。
