Semester

Spring

Date of Graduation

2004

Document Type

Dissertation

Degree Type

PhD

College

School of Medicine

Department

Microbiology, Immunology, and Cell Biology

Committee Chair

Wei-Shau Hu.

Abstract

The work described in these dissertation studies examines three aspects of retrovirus replication and dissects the uncovered phenomena to increase understanding of how retroviruses thrive in complex host environments. The first aspect of replication discussed is the mechanisms behind minus-strand DNA transfer, a crucial step of reverse transcription. We proved for the first time that non-viral sequences can be utilized to carry out this step of the replication process, and that the minus-strand DNA transfer step can be exploited to reconstitute a functional gene in the infected host cell. This finding serves as a proof-of-principle for a new class of self-activating gene therapy vectors. In the second study, mechanisms of trans-complementation were studied between two distantly related retroviruses, murine leukemia virus (MLV) and spleen necrosis virus. We showed that two different species of pol proteins can be incorporated into virions and cooperate to complete the reverse transcription and integration steps of replication. This finding highlights how different species of retroviruses could possibly interact and combine to form new and possibly more virulent or pathogenic species. Finally, in the third work, a previously uninvestigated region of MLV capsid protein was examined. Specifically, the contribution of the 33 carboxyl-terminal amino acids of MLV CA were found to consist of highly charged residues. The contribution of these residues to virus assembly was investigated via deletion analysis. A new phenotype of MLV CA assembly defect was demonstrated, and a structural model was proposed to explain the possible role of this region, termed the charged assembly helix, in MLV assembly. In summary, the work presented in this dissertation has revealed new properties of retroviral replication as well as further clarified previous knowledge of retroviral biology.

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