Ray Swagat, Anderson Emma C
School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK.
Sci Rep. 2016 Mar 3;6:22461. doi: 10.1038/srep22461.
The RNA binding protein Unr, which contains five cold shock domains, has several specific roles in post-transcriptional control of gene expression. It can act as an activator or inhibitor of translation initiation, promote mRNA turnover, or stabilise mRNA. Its role depends on the mRNA and other proteins to which it binds, which includes cytoplasmic poly(A) binding protein 1 (PABP1). Since PABP1 binds to all polyadenylated mRNAs, and is involved in translation initiation by interaction with eukaryotic translation initiation factor 4G (eIF4G), we investigated whether Unr has a general role in translational control. We found that Unr strongly stimulates translation in vitro, and mutation of cold shock domains 2 or 4 inhibited its translation activity. The ability of Unr and its mutants to stimulate translation correlated with its ability to bind RNA, and to interact with PABP1. We found that Unr stimulated the binding of PABP1 to mRNA, and that Unr was required for the stable interaction of PABP1 and eIF4G in cells. siRNA-mediated knockdown of Unr reduced the overall level of cellular translation in cells, as well as that of cap-dependent and IRES-dependent reporters. These data describe a novel role for Unr in regulating cellular gene expression.
RNA结合蛋白Unr含有五个冷休克结构域，在基因表达的转录后调控中具有多种特定作用。它可以作为翻译起始的激活剂或抑制剂，促进mRNA周转，或稳定mRNA。其作用取决于与之结合的mRNA和其他蛋白质，其中包括细胞质聚腺苷酸结合蛋白1（PABP1）。由于PABP1与所有多聚腺苷酸化的mRNA结合，并通过与真核翻译起始因子4G（eIF4G）相互作用参与翻译起始，我们研究了Unr在翻译调控中是否具有普遍作用。我们发现Unr在体外强烈刺激翻译，冷休克结构域2或4的突变会抑制其翻译活性。Unr及其突变体刺激翻译的能力与其结合RNA以及与PABP1相互作用的能力相关。我们发现Unr刺激PABP1与mRNA的结合，并且Unr是细胞中PABP1和eIF4G稳定相互作用所必需的。siRNA介导的Unr敲低降低了细胞中整体的细胞翻译水平，以及帽依赖性和内部核糖体进入位点（IRES）依赖性报告基因的翻译水平。这些数据描述了Unr在调节细胞基因表达中的新作用。
