hide
Free keywords:
-
Abstract:
Remdesivir is the only FDA-approved drug for the treatment of COVID-19 patients. The
active form of remdesivir acts as a nucleoside analog and inhibits the RNA-dependent RNA
polymerase (RdRp) of coronaviruses including SARS-CoV-2. Remdesivir is incorporated by
the RdRp into the growing RNA product and allows for addition of three more nucleotides
before RNA synthesis stalls. Here we use synthetic RNA chemistry, biochemistry and cryo-
electron microscopy to establish the molecular mechanism of remdesivir-induced RdRp
stalling. We show that addition of the fourth nucleotide following remdesivir incorporation
into the RNA product is impaired by a barrier to further RNA translocation. This translocation
barrier causes retention of the RNA 3ʹ-nucleotide in the substrate-binding site of the RdRp
and interferes with entry of the next nucleoside triphosphate, thereby stalling RdRp. In the
structure of the remdesivir-stalled state, the 3ʹ-nucleotide of the RNA product is matched and
located with the template base in the active center, and this may impair proofreading by the
viral 3ʹ-exonuclease. These mechanistic insights should facilitate the quest for improved
antivirals that target coronavirus replication.