Unravelling the Tripartite Interactions Among Hepatitis E Virus RNA, miR-140 and hnRNP K.

In the present investigation, we have identified the functional significance of the highly conserved miR-140 binding site on the Hepatitis E Virus (HEV) genome. Multiple sequence alignment of the viral genome sequences along with RNA folding prediction indicated that the putative miR-140 binding site has significant conservation for sequence and secondary RNA structure among HEV genotypes. Site-directed mutagenesis and reporter assays indicated that an intact sequence of the miR-140 binding site is essential for HEV translation. Provision of mutant miR-140 oligos carrying same mutation as on mutant HEV successfully rescued mutant HEV replication. In vitro cell-based assays with modified oligos proved that host factor-miR-140 is a critical requirement for HEV replication. Biotinylated RNA pulldown and RNA immunoprecipitation assays proved that the predicted secondary RNA structure of the miR-140 binding site allows the recruitment of hnRNP K, which is a key protein of the HEV replication complex. We predicted the model from the obtained results that the miR-140 binding site can serve as a platform for recruitment of hnRNP K and other proteins of HEV replication complex only in the presence of miR-140.