Please use this identifier to cite or link to this item:http://hdl.handle.net/20.500.12105/7885
An RNA trapping mechanism in Alphavirus mRNA promotes ribosome stalling and translation initiation
Nucleic Acids Res. 2016;44(9):4368-80.
During translation initiation, eukaryotic initiation factor 2 (eIF2) delivers the Met-tRNA to the 40S ribosomal subunit to locate the initiation codon (AUGi) of mRNA during the scanning process. Stress-induced eIF2 phosphorylation leads to a general blockade of translation initiation and represents a key antiviral pathway in mammals. However, some viral mRNAs can initiate translation in the presence of phosphorylated eIF2 via stable RNA stem-loop structures (DLP; Downstream LooP) located in their coding sequence (CDS), which promote 43S preinitiation complex stalling on the initiation codon. We show here that during the scanning process, DLPs of Alphavirus mRNA become trapped in ES6S region (680-914 nt) of 18S rRNA that are projected from the solvent side of 40S subunit. This trapping can lock the progress of the 40S subunit on the mRNA in a way that places the upstream initiator AUGi on the P site of 40S subunit, obviating the participation of eIF2. Notably, the DLP structure is released from 18S rRNA upon 60S ribosomal subunit joining, suggesting conformational changes in ES6Ss during the initiation process. These novel findings illustrate how viral mRNA is threaded into the 40S subunit during the scanning process, exploiting the topology of the 40S subunit solvent side to enhance its translation in vertebrate hosts.
Aedes | Alphavirus | Animals | Base Sequence | Cell Line | Codon, Initiator | Cricetinae | Gene Expression Regulation, Viral | Inverted Repeat Sequences | Models, Molecular | RNA Stability | RNA, Messenger | RNA, Ribosomal, 18S | RNA, Viral | Ribosomes | Peptide Chain Initiation, Translational
We are indebted to Luis Menendez′s lab for helping us with acrylamide gels for sequencing and Juanjo Berlanga andMiguel Angel Rodriguez Gabriel for their support and discussions. Institutional support from the Fundacion Ramon Areces is also acknowledged. Completion of this project took approximately 3 years and the estimated cost was 10000 , excluding salaries.
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