| Human mitochondrial DNA (mtDNA), ?our other genome?, was fully sequenced in 1981 and represents a separate genome present at one to several thousands of copies in the mitochondrial network in the cytoplasm of the cell. It encodes thirteen protein subunits of the respiratory chain and ATP synthase, plus the 2 rRNAs and 22 tRNAs required for their synthesis on mitochondrial ribosomes. These being essential subunits for cellular energy production, maintenance of an intact mitochondrial genome is necessary for viability and for the completion of development. MtDNA is organized in foci within the mitochondrial network, termed nucleoids, that typically exist as multiple copies and various proteins that are poorly conserved in evolution. Despite a renewed interest in mtDNA due to its involvement in human disease and ageing, there are still many fundamental questions surrounding faithful copying (replication), repair and inheritance of mtDNA in humans. This research proposal intends to answer some of these questions by the study of mtDNA nucleoids and in doing so aims to also provide a better understanding of the mechanisms by which mtDNA maintenance protein mutations in human disease cause mtDNA instability and loss. More specifically, I will set out to: i) identify and characterize new proteins involved in replication and repair of mtDNA by directed purification of subsets of nucleoids; ii) elucidate properties of nucleoid proteins, in particular membrane association/phospholipid interaction, of importance to understand the mechanisms of replication, repair and inheritance of mtDNA; and iii) establish whether or not nucleoid proteins are modified by post-translational modifications in order to regulate mtDNA maintenance and gene expression. Of particular interest in this case will be three protein-deacetylases of the Sirtuin family that are mitochondrial, believed to be regulated by cellular energy homeostasis, and implicated in longevity. |
