Abstract:
COVID-19, caused by SARS-CoV-2, has been a catastrophic pandemic. While vaccines have
helped restore normalcy, reinfections persist, highlighting the urgent need for antiviral drugs.
The replication transcription complex (RTC) offers a promising target due to its conservation
across strains. The NiRAN (Nidoviruses RdRp associated nucleotidyltransferase) domain of
Nsp 12 (RNA polymerase), which carries out the initial steps of RNA capping, has three
different nucleotide binding poses. Each pose has its own significance for capping viral mRNA
and NMPylation reactions (Nucleotide monophosphate addition to Nsp 9). In this investigation,
using mutagenesis, I tried to delineate the molecular significance of each pose. Additionally,
specific NiRAN residues influence RdRp's extension activity, highlighting their role in RTC
stability and supporting my observations of feeble polymerase activity upon deletion of the
NiRAN domain. These findings contribute to understanding CoV-2 replication and capping
reaction. In addition, my project also provides an RTC mutant for virologists to hunt for the
physiological significance of the NMPylation reaction.
