The relationship between HIV-1 genome RNA dimerization, virion maturation and infectivity

Abstract

The relationship between virion protein maturation and genomic RNA dimerization of human immunodeficiency virus type 1 (HIV-1) remains incompletely understood. We have constructed HIV-1 Gag cleavage site mutants to enable the steady state observation of virion maturation steps, and precisely study Gag processing, RNA dimerization, virion morphology and infectivity. Within the virion maturation process, the RNA dimer stabilization begins during the primary cleavage (p2-NC) of Pr55 Gag. However, the primary cleavage alone is not sufficient, and the ensuing cleavages are required for the completion of dimerization. From our observations, the increase of cleavage products may not put a threshold on the transition from fragile to stable dimeric RNA. Most of the RNA dimerization process did not require viral core formation, and particle morphology dynamics during viral maturation did not completely synchronize with the transition of dimeric RNA status. Although the endogenous virion RT activity was fully acquired at the initial step of maturation, the following process was necessary for viral DNA production in infected cell, suggesting the maturation of viral RNA/protein plays critical role for viral infectivity other than RT process.

Role of the SP2 Domain and Its Proteolytic Cleavage in HIV-1 Structural Maturation and Infectivity

“…Since, however, NC-p6 particles had a much higher proportion of irregular cores than wt particles and the irregular cores occupied a larger fraction of the inner virion volume in both variants, a kinetic delay rather than a failure of RNP condensation may be the cause of irregular capsid formation. NC and NC-SP2 have been shown to be significantly more active nucleic acid chaperones than NC-p6 (11,12,27,32,33,36,43,50), and this chaperone activity is needed to condense the RNA genome into the most thermodynamically stable form. The lower chaperone activity of NC-p6 may translate into delayed condensation of the RNP upon maturation and thereby indirectly affect capsid condensation.…”

HIV-1 Assembly, Budding, and Maturation

“…Analyses of mutant virions with blockages at the different Gag sites indicate that each cleavage event performs a different function. SP1/ NC cleavage activates Env (Wyma et al 2004) and promotes condensation of the RNP particle , SP2 processing frees NC to chaperone formation of the stable genomic RNA dimer (Kafaie et al 2008;Ohishi et al 2011), MA/CA cleavage disassembles the immature lattice and releases CA-SP1, and CA-SP1 cleavage frees CA to form the conical capsid ). In at least some cases, Gag proteolysis induces local conformational changes that favor alternative proteinprotein interactions.…”

A Short Sequence Motif in the 5′ Leader of the HIV-1 Genome Modulates Extended RNA Dimer Formation and Virus Replication

“…The initial RNA-RNA dimer is formed in the virus-producing cell and is subsequently packaged. During virus particle maturation the stability of the HIV-1 RNA dimer increases, which depends on viral Protease activity and processing of the Gag-Pol polyprotein (27,40,43). In general, not much is known about the actual RNA-RNA contacts during virion assembly and subsequent maturation.…”