Translational recoding by chemical modification of non-AUG start codon ribonucleotide bases

Abstract

In contrast to prokaryotes wherein GUG and UUG are permissive start codons, initiation frequencies from non-AUG codons are generally low in eukaryotes, with CUG being considered as strongest. Here, we report that combined 5-cytosine methylation (5mC) and pseudouridylation (Ψ) of near-cognate non-AUG start codons convert GUG and UUG initiation strongly favored over CUG initiation in eukaryotic translation under a certain context. This prokaryotic-like preference is attributed to enhanced NUG initiation by Ψ in the second base and reduced CUG initiation by 5mC in the first base. Molecular dynamics simulation analysis of tRNA i Met anticodon base pairing to the modified codons demonstrates that Ψ universally raises the affinity of codon:anticodon pairing within the ribosomal preinitiation complex through partially mitigating discrimination against non-AUG codons imposed by eukaryotic initiation factor 1. We propose that translational control by chemical modifications of start codon bases can offer a new layer of proteome diversity regulation and therapeutic mRNA technology.

Human TUBA1B short open reading frame product regulates cancer cell growth via importin β

“…Previous studies of duo-coding genes reported that the alternative product from POLG and RPL36 also used CTG and GTG instead of AUG as start codons for translation 28 . Translation initiation from non-AUG codons may involve canonical Kodak sequences 29 , internal ribosome entry sites 30 or chemical modification of codons 31 . This alternative translation initiation appears to have a preference for non-AUG codon-guided initiation.…”

METTL3 as a master regulator of translation in cancer: mechanisms and implications

“…The majority of these marks are enzymatically deposited in a site-specific manner affecting RNA stability, structure, RNA–RNA and RNA–protein interactions ( 10 ). During translation initiation, RNA modifications may guide the recruitment of ribosomes to the start codon, modulating the translation efficiency ( 11 , 12 ). The presence of RNA modifications also defines the secondary structure of the RNA molecule, having a direct impact on the accessibility to ribosomes and other initiation factors to the start codon ( 13 , 14 ).…”