The SARS-Cov-2 pseudoknot interacts with the ribosome and pauses translation upstream of the slippery site. (A) Schematic of the SARS-CoV-2 main ORF. In the close up view of the frameshift event, codons and corresponding amino acids are shown. During -1 frameshifting, the 'slippery site' codons UUA (Leu) and AAC (Asn) are the last codons decoded in the 0 frame. Upon -1 frameshifting of the AAC codon to AAA, translation resumes at the CGG (Arg) triplet, where elongation proceeds uninterrupted to produce full-length Nsp12. (B) In vitro translation reaction depicting pausing at the frameshift site. Efficient frameshifting is observed for the WT template.