内部核糖体进入位点
生物
遗传学
真核翻译
核糖体
假结
真核起始因子
真核核糖体
真核小核糖体亚单位
翻译(生物学)
细胞生物学
核糖核酸
信使核糖核酸
基因
作者
Anna Miścicka,Kristen Lu,Irina S Abaeva,Tatyana V. Pestova,Christopher U.T. Hellen
出处
期刊:RNA
日期:2023-04-11
卷期号:29 (7): 1051-1068
被引量:1
标识
DOI:10.1261/rna.079599.123
摘要
Initiation of translation on many viral mRNAs occurs by noncanonical mechanisms that involve 5' end-independent binding of ribosomes to an internal ribosome entry site (IRES). The ∼190-nt-long intergenic region (IGR) IRES of dicistroviruses such as cricket paralysis virus (CrPV) initiates translation without Met-tRNAiMet or initiation factors. Advances in metagenomics have revealed numerous dicistrovirus-like genomes with shorter, structurally distinct IGRs, such as nedicistrovirus (NediV) and Antarctic picorna-like virus 1 (APLV1). Like canonical IGR IRESs, the ∼165-nt-long NediV-like IGRs comprise three domains, but they lack key canonical motifs, including L1.1a/L1.1b loops (which bind to the L1 stalk of the ribosomal 60S subunit) and the apex of stem-loop V (SLV) (which binds to the head of the 40S subunit). Domain 2 consists of a compact, highly conserved pseudoknot (PKIII) that contains a UACUA loop motif and a protruding CrPV-like stem--loop SLIV. In vitro reconstitution experiments showed that NediV-like IRESs initiate translation from a non-AUG codon and form elongation-competent 80S ribosomal complexes in the absence of initiation factors and Met-tRNAiMet Unlike canonical IGR IRESs, NediV-like IRESs bind directly to the peptidyl (P) site of ribosomes leaving the aminoacyl (A) site accessible for decoding. The related structures of NediV-like IRESs and their common mechanism of action indicate that they exemplify a distinct class of IGR IRES.
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