Allosteric Integrase Inhibitors Reveal a Role for Integrase During HIV-1 Maturation

Abstract

Integration of the DNA copy of the HIV-1 genome is an essential step for virus replication and is mediated by a homotetrameric complex of the viral protein integrase (IN) in association with the ends of linear viral DNA (vDNA). HIV-1 integrates into actively transcribed genes, a trait mediated by cellular host cofactor LEDGF/p75. LEDGF/p75 engages IN in a pocket formed by dimerization of the IN catalytic core domain, a region that has been validated as a drug target for allosteric IN inhibitors (ALLINIs). Previous in vitro work suggested that ALLINIs function through disruption of two integration-associated functions: IN-vDNA complex formation and the IN-LEDGF/p75 interaction. We now demonstrate that ALLINI potency is accounted for during the late phase of HIV-1 replication where the inhibitors block the formation of the viral core, converting the normally electron-dense conical core to an eccentric phenotype where the electron-density exists as a condensate situated between a translucent core and the viral membrane. We have further elucidated the eccentric condensates to represent non-packaged viral ribonucleoprotein (vRNP) complexes and that either genetic or pharmacological inhibition of IN can impair vRNP encapsidation. Supplying IN in trans as part of a Vpr-IN fusion protein partially restored the formation of conical cores with the internal electron density. Moreover the ability of ALLINIs to induce eccentric condensate formation required both IN and viral RNA. Based on these observations, we propose an active role for IN during HIV-1 maturation that involves initiating core morphogenesis and vRNP encapsidation.