Journal Article

HIV-1 nuclear import in macrophages is regulated by CPSF6-capsid interactions at the nuclear pore complex

Glass, Bärbel, Lusic, Marina, Peng, Ke, Kräusslich, Hans-Georg, Laketa, Vibor, Müller, Barbara, Bejarano, David Alejandro, Lucic, Bojana, Börner, Kathleen, Jost, K Laurence

2019

Overview

Nuclear entry of HIV-1 replication complexes through intact nuclear pore complexes is critical for successful infection. The host protein cleavage-and-polyadenylation-specificity-factor-6 (CPSF6) has been implicated in different stages of early HIV-1 replication. Applying quantitative microscopy of HIV-1 reverse-transcription and pre-integration-complexes (RTC/PIC), we show that CPSF6 is strongly recruited to nuclear replication complexes but absent from cytoplasmic RTC/PIC in primary human macrophages. Depletion of CPSF6 or lack of CPSF6 binding led to accumulation of HIV-1 subviral complexes at the nuclear envelope of macrophages and reduced infectivity. Two-color stimulated-emission-depletion microscopy indicated that under these circumstances HIV-1 complexes are retained inside the nuclear pore and undergo CA-multimer dependent CPSF6 clustering adjacent to the nuclear basket. We propose that nuclear entry of HIV-1 subviral complexes in macrophages is mediated by consecutive binding of Nup153 and CPSF6 to the hexameric CA lattice. Viruses are miniscule parasites that hijack the resources of a cell to make more of themselves. For many, this involves getting inside the nucleus, the fortress that protects the cell’s genetic information. To do so, viruses need to first find a way through a double-layered membrane called the nuclear envelope, which only opens up when a cell divides. Yet, the human immunodeficiency virus type 1 (HIV-1) can infect cells that no longer divide, and in which the nucleus’ walls never come down. The virus cores then head for the nuclear pores, heavily guarded holes in the nuclear envelope that allow the cell's own molecules to go in and out of the nucleus. But HIV-1 is too big to fit through, as its genetic information is encased in a capsid, a coat made of a complex assembly of proteins. However, research shows that these capsid proteins can bind to host proteins at the pore or even inside the nucleus. For example, the capsid protein can recognize the pore protein Nup153, or the nuclear protein CPSF6. These interactions could help the virus make its way in, but how these events unfold is still unclear. To explore this, Bejarano, Peng et al. attached fluorescent labels to HIV-1 and watched as it infected non-dividing cells. Rather than completely get rid of their capsid before they crossed the pores, the virus particles hung on to a large part of their lattice. This remaining coat then attached to CPSF6; when this protein was missing or could not bind to capsid proteins, the viral complexes got stuck in the nuclear pores. This suggests that the capsid lattice could first interact with Nup153 inside the pores: then, CPSF6 would take over, knocking Nup153 away and pulling HIV-1 into the nucleus. Armed with this knowledge, virologists and drug developers could try to block HIV-1 from entering the cell’s nucleus; they could also start to dissect how drugs that target the HIV-1 capsid work. Ultimately, HIV-1 may serve as a model to unravel how large objects can pass the nuclear pore, which may help us understand how molecules are constantly trafficked in and out of the nucleus.

• Publisher: eLife Science Publications, Ltd,eLife Sciences Publications Ltd,eLife Sciences Publications, Ltd
• Subject: Active Transport, Cell Nucleus - drug effects / Capsid - drug effects / Capsid - metabolism / Cell Biology / Cell Nucleus - drug effects / Cell Nucleus - metabolism / CPSF6 / Cytoplasm / Genomes / Health aspects / HeLa Cells / HIV / HIV-1 - drug effects / HIV-1 - metabolism / HIV-1 - pathogenicity / Human immunodeficiency virus / Humans / Indoles - pharmacology / Infection / Infections / Infectious diseases / Infectivity / Intercellular Signaling Peptides and Proteins - metabolism / International economic relations / International trade / Labeling / Lasers / Macrophages / Macrophages - drug effects / Macrophages - metabolism / Macrophages - virology / Microbiology and Infectious Disease / Microscopy / mRNA Cleavage and Polyadenylation Factors - metabolism / Mutation / nuclear import / nuclear pore complex / Nuclear Pore Complex Proteins - metabolism / Nuclear transport / Phenylalanine - analogs & derivatives / Phenylalanine - pharmacology / Polyadenylation / pre-integration complex / Protein binding / Proteins / Replication / Scientific equipment industry / Software / Viral proteins / Virology / Virus Internalization - drug effects / Virus replication / Virus Replication - drug effects