Direct Capsid Labeling of Infectious HIV-1 by Genetic Code Expansion Allows Detection of Largely Complete Nuclear Capsids and Suggests Nuclear Entry of HIV-1 Complexes via Common Routes
Sandra Schifferdecker, Vojtěch Žíla, Thorsten G. Müller, Volkan Sakin, Maria Anders‐Össwein, Vibor Laketa, Hans‐Georg Kräusslich, Bárbara Müller
Abstract
The cone-shaped capsid of HIV-1 has recently been recognized as a master organizer of events from cell entry of the virus to the integration of the viral genome into the host cell DNA. Fluorescent labeling of the capsid is essential to study its role in these dynamic events by microscopy, but viral capsid proteins are extremely challenging targets for the introduction of labels. Here we describe a minimally invasive strategy that allows us to visualize the HIV-1 capsid protein in infected cells by live-cell imaging and superresolution microscopy. Applying this strategy, we confirmed that, contrary to earlier assumptions, an equivalent of a complete capsid can enter the host cell nucleus through nuclear pores. We also observed that entering capsids cluster in the nucleus in a dose-dependent manner, suggesting that they may have followed a common entry route to a site suitable for viral genome release.