Hepatitis C virus nonstructural protein 3 helicase (HCV NS3 helicase)

The Hepatitis C virus (HCV) nonstructural protein 3 (NS3) helicase is a critical enzyme located in the C-terminal two-thirds of the bifunctional NS3 protein [2, 9]. It functions as an ATP-dependent molecular motor that unwinds double-stranded RNA (dsRNA) and DNA (dsDNA) intermediates during the viral replication cycle, moving in a 3' to 5' direction [1, 15]. This activity is essential for the synthesis of new viral RNA genomes by the NS5B polymerase, as it resolves secondary structures and displaces bound proteins [2, 6]. While the N-terminal domain of NS3 acts as a serine protease and is the primary target of several FDA-approved direct-acting antivirals (DAAs) such as Glecaprevir and Grazoprevir, the helicase domain remains an attractive but largely untapped therapeutic target [5, 8]. Inhibitors of the NS3 helicase aim to block viral replication by preventing the unwinding of the viral genome [3, 10]. Challenges such as high genetic variability and the need for high potency have limited the clinical advancement of specific helicase inhibitors compared to protease inhibitors [10, 14]. The helicase domain also possesses a robust DNA unwinding activity in vitro, although its primary biological role is focused on the viral RNA genome [6, 15]. Resistance-associated substitutions in the NS3 gene can impact the efficacy of drugs targeting the NS3 protein, necessitating the development of novel inhibitors with high barriers to resistance [8, 13].

Other names

NS3 helicaseNS3 NTPase/helicaseNS3-4A helicase domainHCV NS3hNonstructural protein 3 helicase

Inhibition of ATP-dependent RNA unwinding and viral replication by blocking the helicase domain's catalytic activity or nucleic acid binding site.