The role of mitochondrial transcription factor an in protecting DNA from oxidative damage

Abstract

The mitochondrial transcription factor A (TFAM) is a nuclear encoded high mobility group box protein that is essential for mitochondrial DNA (mtDNA) transcription, replication, and for regulation of mtDNA copy number. TFAM is also directly involved in mtDNA structure and organization through its packaging of mtDNA into nucleoids. TFAM non-specifically binds to and coats the entire mtDNA and packages it into a nucleoproteic complex, similar to the manner in which histones package nuclear DNA. Since the mtDNA is contained in the inner side of the inner mitochondrial membrane, it is prone to oxidative damage by Reactive Oxygen Species (ROS) that accumulate as byproducts of the electron transport chain. It has been suggested that TFAM could play a role in protecting mtDNA from oxidative damage by blocking access to damaging species. On the other hand, we have shown that TFAM binding to DNA delays damage removal by restricting access to DNA repair proteins. In this study we will dissect the role of TFAM in protecting mtDNA from oxidative damage. Furthermore, we propose to investigate how TFAM binding modulates the balance between mtDNA damage and repair, and what protein interacting partners are involved. For this we propose to investigate: i) whether TFAM binding to DNA will protect it form induced oxidative damage by photoactive dyes in vitro; ii) if TFAM levels affect cell survival after induced oxidative damage by photoactive dyes, and iii) protein interactions that modulate TFAM binding to mtDNA. These results will help to determine if TFAM binding to mtDNA protects it from oxidative damage, and how this binding is modulated by possible protein interacting partners. (AU)