ATP-Independent Initiation during Cap-Independent Translation of m6A-Modified mRNA

Abstract

The methylation of adenosine in the N6 position (m6A) is a widely used modification of eukaryotic mRNAs. Its importance for the regulation of mRNA translation was put forward recently, essentially due to the ability of methylated mRNA to be translated in conditions of inhibited cap-dependent translation initiation, e.g., under stress. However, the peculiarities of translation initiation on m6A-modified mRNAs are not fully known. In this study, we used toeprinting and translation in a cell-free system to confirm that m6A-modified mRNAs can be translated in conditions of suppressed cap-dependent translation. We show for the first time that m6A-modified mRNAs display not only decreased elongation, but also a lower efficiency of translation initiation. Additionally, we report relative resistance of m6A-mRNA translation initiation in the absence of ATP and inhibited eIF4A activity. Our novel findings indicate that the scanning of m6A-modified leader sequences is performed by a noncanonical mechanism.

Research Progress in RNA-Binding Proteins

“…For example, it was shown that the wide-spread m 6 A modification in the 5 -UTRs of many messengers enables cap-independent translation under stress conditions [16]. In this Special Issue, Sakharov et al confirm this earlier observation using in vitro translation and toeprinting assays [3]. Furthermore, they find that, while under normal conditions, the initiation and elongation on a methylated mRNA are less efficient, the presence of m 6 A in the 5 -UTR makes the initiation more resistant to the inhibition of the canonical cap-dependent scanning.…”

Protein translation: biological processes and therapeutic strategies for human diseases

“…Modifications in 5' and 3' UTRs as well as deregulation of enzymes involved in cap formation or cap-binding proteins can affect the integrity or availability of the 5' cap. [65][66][67] This disruption can interfere with the recruitment of translation initiation factors like eIF4E and impair the assembly of the translation initiation complex. Besides, dysregulated miRNA expression, modification or aberrant alternative splicing of mRNA, can lead to abnormal translation inhibition or activation of specific genes.…”

Cap-Independent Circular mRNA Translation Efficiency

“…Recently, a firefly luciferase assay was used to demonstrate that m6A-mediated translation initiation is less efficient compared to cap-dependent initiation [ 31 ]. On the other hand, this approach demonstrated comparable results in comparison to IRES-mediated translation initiation [ 32 ].…”