Thesis
High mobility group A1 and mitochondrial transcription factor A compete for binding to mitochondrial DNA
Washington State University
Master of Science (MS), Washington State University
2009
Handle:
https://hdl.handle.net/2376/100539
Abstract
High mobility group A1 (HMGA1) protein functions in the nucleus as a gene regulatory transcription factor. During restricted parts of the normal cell cycle, a subfraction of HMGA1 reversibly translocates to mitochondria. However, HMGA1 is found in both the nucleus and mitochondria throughout the cell cycle of cancerous cells, which almost universally over-express this protein. The exact activities of HMGA1 in mitochondria are currently unknown, but the protein has been demonstrated to bind to the regulatory D-loop region of the mitochondrial DNA (mtDNA) and its over-expression is associated with overall mitochondrial dysfunction. Mitochondrial transcription factor A (TFAM) is a multi-functional high mobility group "B-box" (HMGB) type protein that plays an essential role in a number of routine mitochondrial processes by binding to mtDNA. Because previous findings have shown HMGA1 can out-compete HMGB proteins for DNA binding, it was hypothesized that a competition exists between HMGA1 and TFAM for binding to mtDNA. The ability of HMGA1a to bind to mtDNA and compete with TFAM for mtDNA binding was evaluated using electrophoretic mobility shift assays with B-form mtDNA probes and with synthetic multi-way junctions that mimic proposed Dloop structures. Our findings indicate that HMGA1a has a higher binding affinity for both B-form mtDNA and multi-way junctions as compared to TFAM and that low molar ratios of HMGA1 displace TFAM from these DNA substrates. Chromatin immunoprecipitations verify HMGA1 binding to multiple regions of mtDNA, suggesting this competition likely occurs in vivo. These findings demonstrate for the first time that HMGA1 is able to competitively bind throughout mtDNA, and also suggest a dynamic competition between DNA binding proteins occurs in mitochondria. These data have also led to the proposal of a testable model in which over-expression of HMGA1 leads to its accumulation in mitochondria and allows HMGA1 to out-compete TFAM for binding to mtDNA. Because TFAM binding to mtDNA is essential for a number of routine mitochondrial processes, its displacement by HMGA1 would then lead to overall mitochondrial dysfunction, a phenotype that has long been associated with cancer.
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Details
- Title
- High mobility group A1 and mitochondrial transcription factor A compete for binding to mitochondrial DNA
- Creators
- Kelsey Janel Wertzler
- Contributors
- Raymond Reeves (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Molecular Biosciences, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525391301842
- Language
- English
- Resource Type
- Thesis