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Structural basis for anti-HIV drug toxicity

         Tremendous success fighting human immunodeficiency virus (HIV) replication and transmission with current antiviral drugs must now be balanced against the severe side effects of these reagents.  Antiviral inhibitors of HIV reverse transcriptase interfere with human mitochondrial DNA polymerase leading to cellular and tissue toxicity with respect to key cell biological pathological and pharmacological events. 

We are conducting structural studies of human mitochondrial DNA polymerase in complex with various antiviral inhibitors captured during DNA replication.  Specifically, 1) To elucidate interactions between mitochondrial DNA polymerase and its processivity factor by determination of a co-crystal structure of Pol gA and Pol gB.  2) To capture Pol gAB in the action of replication by determination of complexes structures of Pol gAB with a primer-template DNA substrate.  3) To reveal the inhibitory effects of Pol gAB by determination of structures of Pol gAB-DNA with various anti-HIV reverse transcriptase inhibitors.

Comparison of these structures to the corresponding structures of HIV reverse transcriptase (RT) inhibitors complexes will provide: 1) a framework for understanding the clinical toxicity profile of the various inhibitors, and 2) a rationale for design of HIV-RT inhibitors with minimum adverse reactions.

Mechanism for gene expression in mitochondria

        Mitochondrial dysfunctions have been implicated in numerous human diseases including muscular dystrophy, cardiomyopathy, diabetes and neurodegenerative diseases such as Parkinsonís and Alzheimerís.  Mitochondrial gene expression is essential for the integrity of the organelle.  It is also a central event for coupling mitochondrial gene transcription with DNA replication and protein translation. Mitochondrial transcription machinery consists of a bacteriophage-like RNA polymerase and a set of transcription factors.  However, unlike its bacteriophage ancestor, the mitochondrial RNA polymerase has lost the ability to independently sustain transcription reaction and relies a set the transcription factors for full activity.  Despite the importance of mitochondrial transcription, the knowledge of mitochondrial gene expression is incomplete, no structural or systematic kinetic studies of the mitochondrial transcription machinery are available to understand the interaction between the polymerase and the factors in controlling gene expression. 

We are conducting research to understand the structural and functional aspects of gene expression in mitochondria.  We are trying to address questions as 1) how dose the phage-like, self-sufficient RNA transcription system evolved to be regulated by a set of transcription factors; 2) structural basis for collective and individual roles in promoter recognition and unwinding by the RNA polymerase and transcription factors; and 3) Determine the function roles of Rpo41 and MTF1 in de novo RNA synthesis.

Bioengineering of T7 RNA polymerase for new functions

        T7 RNA polymerase exhibits an amazing structural flexibility as it undergoes large scale refolding and conformational changes when transitions from initiation to elongation phase during a transcription reaction (Figure on the left).  Our research focuses on 1) investigating the folding pathways; 2) engineering T7 RNAP to gain new functions for RNA synthesis, and 3) transcription termination.

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This site was last updated 12/06/07