The Structural Biology of HIV Budding and Maturation

Citation

Dobro, Megan J. (2012) The Structural Biology of HIV Budding and Maturation. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/X6XW-5303. https://resolver.caltech.edu/CaltechTHESIS:06012012-133153407

Abstract

The Human Immunodeficiency Virus (HIV) depends on the ability to exit infected cells, mature into an infectious state, and infect new host cells. The structural details of exiting and maturation (known as the "late stage events") remain elusive, but further understanding could lead to new therapies. HIV exits cells by hijacking a host cellular complex called ESCRT (Endosomal Sorting Complex Required for Transport), which evolved to constrict membranes in multivesicular body formation and cytokinesis. Electron cryotomography (ECT) was used to gain three-dimensional images of ESCRT in several contexts, including the physiological system of archaeal cell division. This study provided insight into the monomer interactions in the complex and led to a molecular mechanism of membrane constriction.

HIV is released from the cell as an immature particle with the main structural protein, Gag, forming a spherical shell around the RNA genome and enzymes. Gag is then cleaved into several proteins that refold and assemble into the conical capsid that is characteristic of the mature, infectious particle. The capsid is typically a closed cone, but unclosed varieties provide insight to the mechanism of assembly. By combining ECT, computer simulations, and fluorescence light microscopy, we analyzed features of unclosed capsids that suggest a "curling sheet" model of capsid assembly. These studies not only provided novel insight into the late stages of the HIV life cycle, but also contributed to the methods used by electron microscopists and researchers of HIV.

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