Modelling the structures of frameshift-stimulatory pseudoknots from representative bat coronaviruses

Abstract

Coronaviruses (CoVs) use −1 programmed ribosomal frameshifting stimulated by RNA pseudoknots in the viral genome to control expression of enzymes essential for replication, making CoV pseudoknots a promising target for anti-coronaviral drugs. Bats represent one of the largest reservoirs of CoVs and are the ultimate source of most CoVs infecting humans, including those causing SARS, MERS, and COVID-19. However, the structures of bat-CoV frameshift-stimulatory pseudoknots remain largely unexplored. Here we use a combination of blind structure prediction followed by all-atom molecular dynamics simulations to model the structures of eight pseudoknots that, together with the SARS-CoV-2 pseudoknot, are representative of the range of pseudoknot sequences in bat CoVs. We find that they all share some key qualitative features with the pseudoknot from SARS-CoV-2, notably the presence of conformers with two distinct fold topologies differing in whether or not the 5′ end of the RNA is threaded through a junction, and similar conformations for stem 1. However, they differed in the number of helices present, with half sharing the 3-helix architecture of the SARS-CoV-2 pseudoknot but two containing 4 helices and two others only 2. These structure models should be helpful for future work studying bat-CoV pseudoknots as potential therapeutic targets.

Tying the knot: Unraveling the intricacies of the coronavirus frameshift pseudoknot

“…An intelligent strategy to prepare for future SARS-CoV-2 variants or novel coronaviruses must leverage evolutionary structure information as well as the hierarchical folding hypothesis , in order to understand the role of initial and subsequent RNA folding within frameshift element mechanics, e.g., our earlier work in predicting secondary structures for the 68 nucleotide (nt) SARS-CoV-2 sequence [ 25 ] (genome coordinates 13475−13542). Searching for commonality of structure features between coronaviruses contributes to broad spectrum pseudoknot therapeutic targeting, evidenced by molecular dynamic simulations of previously unknown 3-D structures for bat-coronavirus frameshift mechanics [ 26 ]. Previous analysis of length-dependent structures in different coronaviruses identified how sequences evolved to support a range of frameshift element structure motifs [ 13 ] (see Section 2.2).…”

Tying the Knot: Unraveling the Intricacies of the Coronavirus Frameshift Pseudoknot

“…An intelligent strategy to prepare for future SARS-CoV-2 variants or novel coronaviruses must leverage evolutionary structure information as well as the hierarchical folding hypothesis , in order to understand the role of initial and subsequent RNA folding within frameshift element mechanics, e.g., our earlier work in predicting secondary structures for the 68 nucleotide (nt) SARS-CoV-2 sequence [21]. Searching for commonality of structure features between coronaviruses contributes to broad spectrum pseudoknot therapeutic targeting, evidenced by molecular dynamic simulations of previously unknown 3-D structures for bat-coronavirus frameshift mechanics [22]. Previous analysis of length-dependent structures in different coronaviruses identified how sequences evolved to support a range of frameshift element structure motifs [9] (cf.…”