A Combined Genetic-Proteomic Approach Identifies Residues within Dengue Virus NS4B Critical for Interaction with NS3 and Viral Replication

Abstract

With no approved therapy or vaccine against dengue virus infection, the viral nonstructural protein 4B (NS4B) represents a possible drug target, because it is indispensable for virus replication. However, little is known about its precise structure and function. Here, we established the first comprehensive genetic interaction map of NS4B, identifying amino acid residues that are essential for virus replication, as well as second-site mutations compensating for their defects. Additionally, we determined the NS4B viral interactome in infected cells and identified the NS3 protease/helicase as a major interaction partner of NS4B. We mapped residues in the cytosolic loop of NS4B as critical determinants for interaction with NS3, as well as RNA replication. The strong correlation between NS3-NS4B interaction and RNA replication provides strong evidence that this complex plays a pivotal role in the viral replication cycle, hence representing a promising antiviral drug target.