All ETDs from UAB

Advisory Committee Chair

Eric Hunter

Advisory Committee Members

David Bedwell

James Collawn

William Britt

Casey Morrow

Document Type

Dissertation

Date of Award

2009

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

The retroviral life cycle is separated into two distinct phases of infection. In the first phase, viral enzymes and proteins allow the virus to establish infection. The virus usurps host machinery in the second stage to produce infectious virus. In both phases of the replication cycle, the envelope (Env) glycoprotein (gp) is a key component of infectivity. Env plays a pivotal role in viral entry, by mediating attachment and facilitating fusion of the viral and cellular membranes, and during assembly, where Env must be incorporated into budding virions in order to produce infectious virions. The Env cytoplasmic domain (CD) interacts with Gag facilitating incorporation. Human immunodeficiency virus type I (HIV-1) gp41 CD is unusually long and characterized by multiple highly conserved motifs that resemble classic trafficking and internalization motifs. The membraneiv proximal tyrosine motif (Y712) has been characterized as the major determinant for internalization, however, there are additional Y (tyrosine) and LL (dileucine) determinants distal to this membrane-proximal signal. The caveat in analyzing the conserved motifs within the CD include the trimeric nature of the Env complex, the interdependence of the gp120 and gp41 ectodomain on the gp41 CD, and the presence of potentially more dominant signals. Considering these limitations, we employed a progressive mutagenesis strategy to comparatively analyze the motifs conserved within the CD. The results presented within this body of work suggest that mutagenesis of the tyrosine (Y) and dileucine (LL)-motifs in the Env CD can influence the biological function of the Env glycoprotein. Evidence supporting the contribution of the conserved motifs in the processes of Env-mediated cell-cell fusion, viral infectivity, viral entry, and incorporation of Env into budding virions is presented. A threshold of virus defect resulting from progressive substitutions in the CD was correlated to motifs overlapping a region of the CD described to play a role in the fusion process. This work brings perspective to the role of the highly conserved motifs of the Env CD in the HIV-1 life cycle. Keywords: Retrovirus, HIV-1, Envelope, cytoplasmic tail, fusion, infectivity.

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