Gallie D R
Department of Biochemistry, University of California, Riverside, CA 92521-0129, USA.
Gene. 1998 Aug 17;216(1):1-11. doi: 10.1016/s0378-1119(98)00318-7.
A quarter of century following the prediction that mRNAs are translated in a circular form, recent biochemical and genetic evidence has accumulated to support the idea that communication between the termini of an mRNA is necessary to promote translation initiation. The poly(A)-binding protein (PABP) interacts with the cap-associated eukaryotic initiation factor (eIF) 4G (in yeast and plants) and eIF4B (in plants), a functional consequence of which is to increase the affinity of PABP for poly(A) and to increase the affinity of the cap-binding complex, eIF4F (of which eIF4G is a subunit) for the 5' cap structure. In mammals, PABP interacts with a novel PABP-interacting protein that also binds eIF4A. The interaction between PABP and those initiation factors associated with the 5' terminus of an mRNA may also explain the role of PABP during mRNA turnover, as it protects the 5' cap from attack by Dcp1p, the decapping enzyme. Several of those mRNAs that have evolved functional equivalents to a cap or a poly(A) tail nevertheless require a functional interaction between terminal regulatory elements similar to that observed between the 5' cap and poly(A) tail, suggesting that efficient translation is predicated on communication between largely-separated regulatory elements within an mRNA.
在预测mRNA以环形形式进行翻译的四分之一个世纪之后，最近积累的生化和遗传学证据支持了这样一种观点，即mRNA末端之间的通讯对于促进翻译起始是必要的。聚腺苷酸结合蛋白（PABP）与帽结合相关的真核起始因子（eIF）4G（在酵母和植物中）以及eIF4B（在植物中）相互作用，其功能结果是增加PABP对聚腺苷酸的亲和力，并增加帽结合复合物eIF4F（eIF4G是其亚基之一）对5'帽结构的亲和力。在哺乳动物中，PABP与一种新型的PABP相互作用蛋白相互作用，该蛋白也结合eIF4A。PABP与那些与mRNA 5'末端相关的起始因子之间的相互作用也可能解释了PABP在mRNA周转过程中的作用, 因为它保护5'帽免受脱帽酶Dcp1p的攻击。那些已经进化出与帽或聚腺苷酸尾巴功能等效物的mRNA中的一些仍然需要末端调控元件之间的功能性相互作用，类似于在5'帽和聚腺苷酸尾巴之间观察到的相互作用，这表明有效的翻译取决于mRNA内大部分分离的调控元件之间的通讯。
