Hierarchical multi-step organization during viral capsid assembly.
Formation of the HIV-1 core by the association of capsid proteins is a critical, not fully understood, step in the viral life cycle. Understanding the early stages of the mechanism may improve treatment opportunities. Here, spectroscopic analysis (opacity) is used to follow the kinetics of capsid protein assembly, which shows three stages: a lag phase, followed by a linear increase stage and terminated by a plateau. Adding pre-incubated capsid proteins at the start of the lag phase shortens it and increases the rate of assembly at the linear stage, demonstrating autoacceleration and cooperative assembly. Cryogenic transmission electron microscopy is used to probe structural evolution at these three stages. At the beginning of the lag phase, short tubular assemblies are found alongside micron long tubes. Their elongation continues all throughout the lag phase, at the end of which tubes start to assemble into bundles. Based on these results, we suggest a multi-step self-assembly process including fast nucleation and elongation followed by tubes packing into arrays.
Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel.
Ayala
A
Lampel
Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel.
Maxim
M
Varenik
Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel; Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel. Electronic address: oregev@bgu.ac.il.
Oren
O
Regev
Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel; Department of Materials Science and Engineering, Iby and Aladar Fleischman Faculty of Engineering, Tel Aviv University, Tel Aviv 6997801, Israel. Electronic address: ehudg@post.tau.ac.il.
Ehud
E
Gazit
D002213:Capsid; D015497:HIV-1 / Q000502:physiology*; D046529:Microscopy, Electron, Transmission; D019065:Virus Assembly
Capsid; Cryo-TEM; HIV; Mechanism; Self-assembly