Molecular Determinants of PQBP1 Binding to the HIV-1 Capsid Lattice

Human immunodeficiency virus type 1 (HIV-1) stimulates innate immune responses upon infection, including cyclic GMP-AMP synthase (cGAS) signaling that results in type I interferon production. HIV-1-induced activation of cGAS requires the host cell factor polyglutamine binding protein 1 (PQBP1), an intrinsically disordered protein that bridges capsid recognition and cGAS recruitment. However, the molecular details of PQBP1 interactions with the HIV-1 capsid and their functional implications remain poorly understood. Here, we show that PQBP1 binds to HIV-1 capsids through charge complementing contacts between acidic residues in the N-terminal region of PQBP1 and an arginine ring in the central channel of the HIV-1 CA hexamer that makes up the viral capsid. These studies reveal the molecular details of PQBP1's primary interaction with the HIV-1 capsid and suggest that additional elements are likely to contribute to stable capsid binding.