N6-methyladenosine in mRNA disrupts tRNA selection and translation-elongation dynamics

Abstract

N6-methylation of adenosine (m6A) is the most abundant post-transcriptional modification within the coding region of mRNA, but its role during translation remains unknown. Here, we used bulk kinetic and single-molecule methods to probe the effect of m6A in mRNA decoding. Although m6A base pairs with uridine during decoding as shown by x-ray crystallographic analyses of Thermus thermophilus ribosomal complexes, our measurements employing an Escherichia coli translation system revealed that m6A modification of mRNA can act as a barrier to tRNA accommodation and translation elongation. The interaction between an m6A-modified codon and cognate tRNA echoes the interaction between a near-cognate codon and tRNA, as delay in tRNA accommodation depends on the position and context of m6A within codons and on the accuracy level of translation. Overall, our results demonstrate that chemical modification of mRNA can change translational dynamics.

Post-transcriptional gene regulation by mRNA modifications

“…Transcriptome-wide RNA structure mapping has confirmed that methylated RNA regions prefer single-stranded structures to double-stranded structures 70,72–74 . In addition, a recent report revealed that m 6 A within coding regions could induce steric constraints that destabilize pairing between codons and tRNA anticodons, thus affecting translation dynamics 75 .…”

mRNA modifications: Dynamic regulators of gene expression?

“…Thereby, m 5 C placed at the 2 nd position of a CCC codon, resulted in a substitution of proline by leucine. Importantly, this partial “recoding” was also strongly dependent on the position of the modification within the codon and might also be influenced by the sequence context, similar to m 6 A 38 . Thus, additional experiments will be required to identify mechanisms how m 5 C interferes with ribosomal decoding.…”

Pseudouridine: the fifth RNA nucleotide with renewed interests

“…It is worth noting that during the revision of this review, the Yu group report that Cs in U2 snRNA contribute to premRNA splicing by altering the binding/ATPase activity of Prp5, representing the first example of C directly influencing protein binding [58 ]. Additionally, the presence of C could alter the dynamics of translating ribosomes, as has been recently shown for m 6 A [59]. Whether or not C could affect the stability of mRNA is also open for future investigation; since under heat shock conditions an association of pseudouridylation and stability of mRNA transcripts has been reported [2 ].…”