The COVID-19 pandemic revealed a need for new understanding of the mechanisms regulating host-pathogen interactions during viral infection. Transfer RNA-derived RNAs (tDRs), previously called transfer RNA fragments (tRFs), have recently emerged as potential regulators of viral pathogenesis. Many predictive studies using bioinformatic approaches have been conducted providing a repertoire of potential small RNA candidates for further analyses; however, few targets have been validated to directly bind to SARS-CoV-2 sequences. In this study, we used available data sets to identify host tDR expression altered in response to SARS-CoV-2 infection. RNA-interaction-prediction tools were used to identify sequences in the SARS-CoV-2 genome where tDRs could potentially bind. We then developed luciferase assays to confirm direct regulation through a predicted region of SARS-CoV-2 by tDRs. We found that two tDRs were downregulated in both clinical and in vitro cell culture studies of SARS-CoV-2 infection. Binding sites for these two tDRs were present in the 3' untranslated region (3'UTR) of the SARS-CoV-2 reference virus and both sites were altered in Variants of Concern (VOCs) that emerged later in the pandemic. These studies directly confirm the binding of human tDRs to a specific region of the 3'UTR of SARS-CoV-2 providing evidence for a novel mechanism for host-pathogen regulation.
Keywords: SARS-CoV-2; VOCs; Variants of Concern; host-viral interactions; small noncoding RNA; tDR; tRF; tRNA fragments; tRNA-derived RNAs.