Protein Dynamics at the Mitochondrial Replication Fork |
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| Air date: | Wednesday, January 09, 2008, 3:00:00 PM |
| Category: | Wednesday Afternoon Lectures |
| Runtime: | 60 minutes |
| NLM Title: | Protein dynamics at the mitochondrial replication fork [electronic resource] / Laurie Kaguni. |
| Series: | NIH director's Wednesday afternoon lecture series |
| Author: | Kaguni, Laurie. National Institutes of Health (U.S.) |
| Publisher: | [Bethesda, Md. : National Institutes of Health, 2008] |
| Other Title(s): | NIH director's Wednesday afternoon lecture series |
| Abstract: | (CIT): The mitochondrial replicase (pol gamma) comprises two subunits, a large catalytic core (pol gamma-alpha) and a smaller accessory subunit (pol gamma-betta) that enhances holoenzyme activity and processivity. Mutagenesis of four conserved sequence elements located within the spacer region between the DNA polymerase and 3'-5' exonuclease active sites in pol gamma-alpha demonstrates their functional roles in holoenzyme activity, processivity and/ or DNA binding affinity. Several mutations also affect differentially DNA polymerase and exonuclease activity, and/ or functional interactions with mitochondrial single-stranded DNA-binding protein (mtSSB). Overexpression of the catalytic core in the nervous system of Drosophila induces severe mtDNA depletion and reduces median life span. A parallel mutagenesis of the human accessory subunit, in combination with the determination of its crystal structure and molecular modeling, elucidates its role as a novel type of processivity factor. Loss of function alleles result in mtDNA depletion and developmental lethality in Drosophila. A human pol gamma/DNA complex model was developed using the structures of the pol gamma beta dimer and the T7 DNA polymerase ternary complex, which suggests multiple regions of subunit interaction between pol gamma beta and the human catalytic core that allow it to encircle the newly synthesized double-stranded DNA, and thereby enhance DNA binding affinity and holoenzyme processivity. Functional complexes of pol gamma, mtSSB and a novel mitochondrial DNA helicase reconstitute the mitochondrial DNA replication fork. The human mtDNA helicase exists as a hexamer/ heptamer and exhibits a modular architecture that is highly similar to that of bacteriophage T7 primase-helicase and E. coli DnaB protein. Molecular analysis of active site and selected human disease alleles of the Drosophila homolog by overexpression in Schneider cells results in a dominant-negative lethal phenotype resulting from mtDNA depletion. This work was supported by NIH grant GM45295. For more information, visit http://www.bch.msu.edu/faculty/kagunil.htm NIH Director's Wednesday Afternoon Lecture. |
| Subjects: | DNA Replication DNA, Mitochondrial--genetics DNA-Directed DNA Polymerase Mitochondrial Diseases Mitochondrial Proteins |
| Publication Types: | Government Publications Lectures |
| Download: | Download
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| NLM Classification: | QU 58.5 |
| NLM ID: | 101465430 |
| CIT File ID: | 14228 |
| CIT Live ID: | 6205 |
| Permanent link: | http://videocast.nih.gov/launch.asp?14228 |
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Enhanced Audio Podcast | 51:27 |
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Enhanced Video Podcast | 51:27 | |