Date of Award
HIV-1 integrase, viral nuclear import, HIV-1 inhibitors
Early events in the viral replication cycle of the human immunodeficiency virus (HIV) determine the virus' ability to sustain a persistent infection in susceptible host species. However, many of the molecular machinations through which the virus progresses during its earliest moments in the cell's interior remain enigmatic. Similar to other virus families, HIV virions are packed with a specific assortment of viral and cellular proteins that allow them to carry out their unique program for replication inside of target cells. One such protein that is present in incoming virions, HIV-1 integrase, is an enzyme that facilitates the fusion of the viral genome and the host genomic DNA in the nucleus, thereby making HIV a permanent fixture in infected individuals. We have discovered that, in addition to its role in catalyzing integration, the HIV-1 integrase plays key part in transporting the viral DNA through the cytoplasm to the nucleus during a process known as viral nuclear import. Viral nuclear import is a key early step in the viral life cycle directly preceding integration that has to date been exploited as a target for antiretroviral therapy. Our recent studies indicate that a small stretch of sequence within the carboxyl terminus of the HIV-1 integrase protein contains a nuclear localization signal (NLS) that is indispensable for viral nuclear import and therefore absolutely required for productive HIV infection. Importantly, we have identified several mutations (NLS mutants) within this region that can disrupt nuclear import and therefore completely stall HIV infection. In addition, alignment of all the known subtypes of HIV within the region specified by our NLS mutants indicates that the virus seldom changes its sequence in this part of its genome, suggesting that this domain is a critical factor that it must preserve for optimal infection. Thus, a major focus of this thesis is to clarify the role that the HIV integrase plays in nuclear import. In turn, these analyses may provide a rational basis for the design of new experimental drug screening systems dedicated to finding inhibitors that block HIV-1 nuclear import and curtail HIV infection. A secondary aim of this work is to understand the mechanism of species-specific restriction of lentivirus infection in primates mediated by endogenous host cell restriction factors such as Lvl/TRIM5-a. Lastly, a potential role for non-pathogenic viral DNA episomal circles formed from integration-defective HIV virions as a novel platform for gene therapy based vaccines is discussed.
Cunningham, Tshaka J., "Exploring the Early Events in the HIV-1 Life Cycle: From Post-Entry Restriction to Nuclear Import" (2005). Student Theses and Dissertations. 46.