In silico structure analysis of alphaviral RNA genomes shows diversity in the evasion of IFIT1-mediated innate immunity

The IFIT (interferon-induced proteins with tetratricopeptide repeats) family constitutes a major arm of the antiviral functionof type I interferon (IFN). Human IFIT1, the earliest discovered member of this family, inhibits several viruses of positivestrand RNA genome. IFIT1 specifically recognizes single-stranded RNA with canonical 7-methylguanylate cap at the 50 end(Cap0), and inhibits their translation by competing with eIF4E (eukaryotic initiation factor 4E), an essential factor for 50Caprecognition. Recently, a novel viral mechanism of IFIT1 suppression was reported, in which an RNA hairpin in the 50untranslated region (50UTR) of the viral genome prevented recognition by IFIT1 and enhanced virus growth. Here, I haveanalyzed the in silico predicted structures in the 50UTR of the genomes of the Alphaviruses, a large group of envelopedRNA virus with positive-sense single-stranded genome. The results uncovered a large ensemble of RNA secondarystructures of diverse size and shape in the different viruses, which showed little correspondence to the phylogeny of theviruses. Unexpectedly, the 50UTR of several viral genomes in this family did not fold into any structure, suggesting eithertheir extreme sensitivity to IFIT1 or the existence of alternative viral mechanisms of subverting IFIT1 function.

Novel sequence variations in LAMA2 and SGCG genes modulating cis-acting regulatory elements and RNA secondary structure

In this study, we detected new sequence variations in LAMA2 and SGCG genes in 5 ethnic populations, and analysed their effect on enhancer composition and mRNA structure. PCR amplification and DNA sequencing were performed and followed by bioinformatics analyses using ESEfinder as well as MFOLD software. We found 3 novel sequence variations in the LAMA2 (c.3174+22_23insAT and c.6085 +12delA) and SGCG (c.*102A/C) genes. These variations were present in 210 tested healthy controls from Tunisian, Moroccan, Algerian, Lebanese and French populations suggesting that they represent novel polymorphisms within LAMA2 and SGCG genes sequences. ESEfinder showed that the c.*102A/C substitution created a new exon splicing enhancer in the 3'UTR of SGCG genes, whereas the c.6085 +12delA deletion was situated in the base pairing region between LAMA2 mRNA and the U1snRNA spliceosomal components. The RNA structure analyses showed that both variations modulated RNA secondary structure. Our results are suggestive of correlations between mRNA folding and the recruitment of spliceosomal components mediating splicing, including SR proteins. The contribution of common sequence variations to mRNA structural and functional diversity will contribute to a better study of gene expression.