Sawicka Kirsty, Bushell Martin, Spriggs Keith A, Willis Anne E
Centre for Biomolecular Sciences, School of Pharmacy, University of Nottingham, University Park, Nottingham, UK.
Biochem Soc Trans. 2008 Aug;36(Pt 4):641-7. doi: 10.1042/BST0360641.
PTB (polypyrimidine-tract-binding protein) is a ubiquitous RNA-binding protein. It was originally identified as a protein with a role in splicing but it is now known to function in a large number of diverse cellular processes including polyadenylation, mRNA stability and translation initiation. Specificity of PTB function is achieved by a combination of changes in the cellular localization of this protein (its ability to shuttle from the nucleus to the cytoplasm is tightly controlled) and its interaction with additional proteins. These differences in location and trans-acting factor requirements account for the fact that PTB acts both as a suppressor of splicing and an activator of translation. In the latter case, the role of PTB in translation has been studied extensively and it appears that this protein is required for an alternative form of translation initiation that is mediated by a large RNA structural element termed an IRES (internal ribosome entry site) that allows the synthesis of picornaviral proteins and cellular proteins that function to control cell growth and cell death. In the present review, we discuss how PTB regulates these disparate processes.
多嘧啶序列结合蛋白（PTB）是一种普遍存在的RNA结合蛋白。它最初被鉴定为一种在剪接中起作用的蛋白质，但现在已知它在大量不同的细胞过程中发挥作用，包括聚腺苷酸化、mRNA稳定性和翻译起始。PTB功能的特异性是通过该蛋白细胞定位的变化（其从细胞核穿梭到细胞质的能力受到严格控制）及其与其他蛋白质的相互作用共同实现的。这种定位和反式作用因子需求的差异解释了PTB既作为剪接抑制因子又作为翻译激活因子的事实。在后一种情况下，PTB在翻译中的作用已得到广泛研究，似乎这种蛋白质是一种由称为内部核糖体进入位点（IRES）的大型RNA结构元件介导的翻译起始替代形式所必需的，该元件允许合成微小RNA病毒蛋白以及在控制细胞生长和细胞死亡中起作用的细胞蛋白。在本综述中，我们讨论了PTB如何调节这些不同的过程。
