The impact of host microRNAs on the development of conserved mutations of SARS-CoV-2.

SARS-CoV-2, the virus responsible for the COVID-19 pandemic, has undergone various genetic alterations due to evolutionary pressures exerted by host cells, including intracellular antiviral mechanisms such as targeting by human microRNAs (miRNAs). This study investigates the impact of miRNAs hsa-miR-3132 and hsa-miR-4650 on the viral genome. Sequence alignment revealed conserved mutations in the binding sites of these miRNAs in adapted strains compared to the original Wuhan-Hu-1 strain, leading to their deletion. Despite modest expression of these miRNAs in SARS-CoV-2 target tissues, their efficacy against mutant strains is reduced due to the loss of binding sites. Structural analysis indicates that the mutant genome is more stable than the Wuhan-Hu-1 genome. Luciferase and virus titration assays demonstrate that hsa-miR-3132 and hsa-miR-4650 effectively target the Nsp3 gene in the Wuhan-Hu-1 strain but not in mutant strains lacking their binding sites. These findings suggest that the observed mutations help the virus evade selective pressure from human miRNAs, contributing to its adaptation.