Abstract:
MicroRNAs (miRNAs) are small non-coding RNAs with approximately 22 nucleotides in length which play an important role in regulation of gene expression. Mature miRNAs are involved in many cellular processes including inhibition of infected viral replication. In this study, three subtypes of influenza A viruses (pH1N1, H5N1 and H3N2) which naturally infected human were analyzed by computational approaches to find candidate human cellular miRNAs targeting viral genomes. Candidate human miRNAs were predicted by two human miRNA prediction databases: miRBase and RNAhybrid. The candidate human miRNAs were analyzed based on minimum free energy (MFE) and hybridization patterns between the selected mature miRNAs and viral target genes. The candidate miRNA was selected for constructing miRNA expression vector and reporter-target vector (viral gene at 3'-UTR of Firefly Luciferase). In vitro analysis was done by 3'UTR reporter assay in A549 cells. Relative luciferase activity was measured from transfected cells. According to the in silico analysis, there were 76 miRNAs targeting influenza A viruses. Among these candidates, 70 miRNAs were specifically targeting each subtype of influenza A virus including 21 miRNAs targeted H1N1 subtype, 27 miRNAs targeted H5N1 subtype and 22 miRNAs targeted H3N2 subtype. The remaining 6 miRNAs targeted on multiple subtypes of influenza A viruses. Obviously, most of the candidate miRNAs are targeting on polymerase complex genes (PB2, PB1 and PA) of influenza A viruses. Interestingly, hsa-miR-3145 is the only candidate miRNA targeting PB1 gene of all three subtypes of influenza A viruses. The ability of hsa-miR-3145 inhibiting viral PB1 was tested by 3'UTR reporter assay in A549 cells. The results found that relative luciferase activity was decreased significantly in A549 cells transfected with miRNA expression vector (p-value=0.007). hsa-miR-3145 specifically targeting to viral PB1 gene which inserted at 3'UTR of firefly luciferase resulted in the reduction of relative luciferase activity. It indicated that hsa-miR-3145 targeting viral PB1 gene may downregulate the expression of viral PB1 gene and inhibit the replication of influenza A virus.