title: Reverse Transcription Mechanically Initiates HIV-1 Capsid Disassembly.
abstract: The HIV-1 core consists of the viral genomic RNA and several viral proteins encased within a conical capsid. After cell entry, the core disassembles in a process termed uncoating. Although HIV-1 uncoating has been linked to reverse transcription of the viral genome in target cells, the mechanism by which uncoating is initiated is unknown. Using time-lapse atomic force microscopy, we analyzed the morphology and physical properties of isolated HIV-1 cores during the course of reverse transcriptionin vitroWe found that, during an early stage of reverse transcription the pressure inside the capsid increases, reaching a maximum after 7 h. High-resolution mechanical mapping reveals the formation of a stiff coiled filamentous structure underneath the capsid surface. Subsequently, this coiled structure disappears, the stiffness of the capsid drops precipitously to a value below that of a pre-reverse transcription core, and the capsid undergoes partial or complete rupture near the narrow end of the conical structure. We propose that the transcription of the relatively flexible single-stranded RNA into a more rigid filamentous structure elevates the pressure within the core, which triggers the initiation of capsid disassembly.IMPORTANCEFor successful infection, the HIV-1 genome, which is in the form of a single-stranded RNA enclosed inside a capsid shell, must be reverse transcribed into double-stranded DNA and released from the capsid (in a process known as uncoating) before it can be integrated into the target cell genome. The mechanism that triggers uncoating is a pivotal question of long standing. By using atomic force microscopy, we found that during reverse transcription the pressure inside the capsid increases until the internal stress exceeds the strength of the capsid structure and the capsid breaks open. The application of AFM technologies to study purified HIV-1 cores represents a new experimental platform for elucidating additional aspects of capsid disassembly and HIV-1 uncoating.
authors.affiliation: Department of Physiology and Cell Biology, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors.forename: Sanela
authors.initials: S
authors.lastname: Rankovic
authors.affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
authors.forename: Janani
authors.initials: J
authors.lastname: Varadarajan
authors.affiliation: Department of Physiology and Cell Biology, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors.forename: Ruben
authors.initials: R
authors.lastname: Ramalho
authors.affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Aiken
authors.affiliation: Department of Physiology and Cell Biology, Ben-Gurion University of the Negev, Beer-Sheva, Israel roussoi@bgu.ac.il.
authors.forename: Itay
authors.identifier: http://orcid.org/0000-0002-4399-9171
authors.initials: I
authors.lastname: Rousso
mesh_terms: D001274:Atmospheric Pressure; D002213:Capsid / Q000737:chemistry / Q000378:metabolism*; D036022:Capsid Proteins / Q000235:genetics; D002460:Cell Line; D015497:HIV-1 / Q000235:genetics* / Q000378:metabolism; D054884:Host-Pathogen Interactions; D006801:Humans; D018625:Microscopy, Atomic Force; D048348:Reverse Transcription; D059008:Time-Lapse Imaging; D014764:Viral Proteins / Q000378:metabolism; D014771:Virion / Q000235:genetics; D057646:Virus Uncoating
chemical_list: D036022:Capsid Proteins; D014764:Viral Proteins
keywords: HIV-1; atomic force microscopy; capsid; reverse transcription; uncoating