Yueh A, Schneider R J
Department of Microbiology, New York University School of Medicine, New York, New York 10016 USA.
Genes Dev. 2000 Feb 15;14(4):414-21.
Translation initiation on eukaryotic mRNAs involves 40S ribosome association with mRNA caps (m(7)GpppN), mediated by initiation factor eIF4F. 40S eukaryotic ribosomes and initiation factors undergo 5' scanning to the initiation codon, with no known role for complementarity between eukaryotic 18S rRNA and the 5' noncoding region of mRNAs. We demonstrate that the 5' noncoding region of human adenovirus late mRNAs, known as the tripartite leader, utilizes a striking complementarity to 18S rRNA to facilitate a novel form of translation initiation referred to as ribosome shunting, in which 40S ribosomes bind the cap and bypass large segments of the mRNA to reach the initiation codon. Related elements are also shown to promote ribosome shunting in adenovirus IVa2 intermediate phase mRNA during virus infection and in human heat shock protein 70 (hsp70) mRNA for selective translation during heat shock. The importance of mRNA complementarity to 18S rRNA suggests that ribosome shunting may involve either specific RNA structural features or a prokaryotic-like interaction between mRNA and rRNA.
真核生物mRNA的翻译起始涉及40S核糖体与mRNA帽（m(7)GpppN）的结合，这一过程由起始因子eIF4F介导。40S真核核糖体和起始因子会对起始密码子进行5'端扫描，目前尚不清楚真核18S rRNA与mRNA的5'非编码区之间的互补性在此过程中发挥何种作用。我们证明，人腺病毒晚期mRNA的5'非编码区，即所谓的三联前导序列，利用与18S rRNA显著的互补性来促进一种新的翻译起始形式，即核糖体跳跃，在此过程中40S核糖体结合帽结构并跳过mRNA的大部分区域以到达起始密码子。相关元件在病毒感染期间也能促进腺病毒IVa2中期mRNA中的核糖体跳跃，以及在热休克期间促进人热休克蛋白70（hsp70）mRNA的选择性翻译。mRNA与18S rRNA互补性的重要性表明，核糖体跳跃可能涉及特定的RNA结构特征，或者mRNA与rRNA之间类似原核生物的相互作用。
