Role of N6-methyladenosine in expression of Rous sarcoma virus RNA: analyses utilizing immunoglobulin specific for N6-methyladenosine

Epitranscriptomic regulation of viral replication

RNA plays central roles in biology and novel functions and regulation mechanisms are constantly emerging. To accomplish some of their functions within the cell, RNA molecules undergo hundreds of chemical modifications from which N6-methyladenosine (m⁶A), inosine (I), pseudouridine (ψ) and 5-methylcytosine (5mC) have been described in eukaryotic mRNA. Interestingly, the m⁶A modification was shown to be reversible, adding novel layers of regulation of gene expression through what is now recognized as epitranscriptomics. The development of molecular mapping strategies coupled to next generation sequencing allowed the identification of thousand of modified transcripts in different tissues and under different physiological conditions such as viral infections. As intracellular parasites, viruses are confronted to cellular RNA modifying enzymes and, as a consequence, viral RNA can be chemically modified at some stages of the replication cycle. This review focuses on the chemical modifications of viral RNA and the impact that these modifications have on viral gene expression and the output of infection. A special emphasis is given to m⁶A, which was recently shown to play important yet controversial roles in different steps of the HIV-1, HCV and ZIKV replication cycles.

A Method for Measuring RNA N 6-methyladenosine Modifications in Cells and Tissues

N⁶-Methyladenosine (m⁶A) modifications of RNA are diverse and ubiquitous amongst eukaryotes. They occur in mRNA, rRNA, tRNA, and microRNA. Recent studies have revealed that these reversible RNA modifications affect RNA splicing, translation, degradation, and localization. Multiple physiological processes, like circadian rhythms, stem cell pluripotency, fibrosis, triglyceride metabolism, and obesity are also controlled by m⁶A modifications. Immunoprecipitation/sequencing, mass spectrometry, and modified northern blotting are some of the methods commonly employed to measure m⁶A modifications. Herein, we present a northeastern blotting technique for measuring m⁶A modifications. The current protocol provides good size separation of RNA, better accommodation and standardization for various experimental designs, and clear delineation of m⁶A modifications in various sources of RNA. While m⁶A modifications are known to have a crucial impact on human physiology relating to circadian rhythms and obesity, their roles in other (patho)physiological states are unclear. Therefore, investigations on m⁶A modifications have immense possibility to provide key insights into molecular physiology.