Identification of a DNA binding protein in highly-pure and functional mitochondrial nucleoids.

Abstract

Mitochondrial DNA (mtDNA) is packed into highly organized structures called mitochondrial nucleoids (mt-nucleoids). Physarum polycephalum has highly developed mt-nucleoids and we can isolate them keeping the function as in vivo. Isolated mt-nucleoid consists of at least 70 kinds of proteins. In those proteins, we identified 56kDa-protein (p56) as a DNA binding protein. It has homology with an Yeast mt-nucleoid protein, Mgm101, which is essential for mtDNA maintenance.
p56 showed the sequence-nonspecific and direct DNA-binding activity. Moreover, immunofluorescence and immunoblot analysis revealed that the p56 localized throughout the mt-nucleoid. Furthermore, we developed methods for microinjection into the plasmodium. The knockdown analysis of p56 by microinjection resulted in accumulation of DNA mutation due to oxidation induction medicine and in the increased expression level of certain DNA repair protein. Now, we are studying about the detail on the involvement of the p56 in DNA repair function.