Identification of RNA Pseudoknot-Binding Ligand That Inhibits the-1 Ribosomal Frameshifting of SARS-Coronavirus by Structure-Based Virtual Screening

Programmed -1 ribosomal frameshifting (-1 RF) is an essential regulating mechanism of translation used by SARS-CoV (severe acute respiratory syndrome coronavirus) to synthesize the key replicative proteins encoded by two overlapping open reading frames. The integrity of RNA pseudoknot stability and structure in the -1 RF site is important for efficient -1 RF. Thus, small molecules interacting with high affinity and selectivity with the RNA pseudoknot in the -1 RF site of SARS-CoV (SARS-pseudoknot) would disrupt -1 RF and be fatal to viral infectivity and production. To discover ligands for the SARS-pseudoknot by virtual screening, we constructed a 3D structural model of the SARS-pseudoknot and conducted a computational screening of the chemical database. After virtual screening of about 80 000 compounds against the SARS-pseudoknot structure, high-ranked compounds were selected and their activities were examined by in vitro and cell-based -1 RF assay. We successfully identified a novel ligand 43 that dramatically inhibits the -1 RF of SARS-CoV. This antiframeshift agent is an interesting lead for the design of novel antiviral agents against SARS-CoV.