Elucidating the role of HIV-1 integrase in viral maturation

Project Summary Maturation during the HIV life cycle consists of the viral Gag and Gag-Pol polyproteins undergoing sequential proteolysis to create mature proteins, which organize into a functional viral core having the viral genomic RNA (gRNA) condensed as a ribonucleoprotein particle (RNP) inside the mature capsid. Eccentric condensate (EC) phenotypes, consist of the RNP localized outside the capsid, lead to loss of infectivity. The EC phenotype is caused by antivirals that target both the viral CA and IN proteins; additionally, this has been shown in so-called class II IN mutants. Recent work has shown that IN can bind to gRNA, indicating that IN has a critical role in the maturation process and gRNA encapsidation. In accordance with previous findings, we hypothesize that IN acts as a physical bridge between the gRNA and assembling CA. Consistent with this hypothesis, preliminary data that we have collected suggests that IN binds to CA hexamers. Furthermore, cryoEM analyses indicate that IN likely binds to the C-terminal domain (CTD) of CA, causing a shift in CTD-CTD organization as the capsid assembles. Finally, RNPs purified from bona fide virions can be reencapsidated with recombinant CA that is assembled de novo. Further investigations proposed in this F32 application aim to uncover a detailed mechanistic binding scheme of IN and CA and will utilize complementary structural biology and biophysical techniques. The results are expected to further our understanding of the maturation process of HIV and possibly identify an attractive new target for antivirals.