Regulation of mitochondrial D-loops by transcription factor A and single-stranded DNA-binding protein.
Takamatsu C, Umeda S, Ohsato T, Ohno T, Abe Y, Fukuoh A, Shinagawa H, Hamasaki N, Kang D
EMBO Reports (2002)
Category: mitochondrial DNA ¤ Added: May 09, 2002 ¤ Rating:
During replication, mtDNA takes on a triple-stranded structure called a D-loop. Although their physiological roles are not understood, D-loops are implicated in replication and transcription of mtDNA. Little is known about the turnover of D-loops. We investigated the effects of mitochondrial transcription factor A (TFAM) and single-stranded DNA-binding protein (mtSSB) on D-loops. In human HeLa cells, TFAM and mtSSB are, respectively, 1700- and 3000-fold more abundant than mtDNA. This level of TFAM is two orders of magnitude higher that reported previously and is sufficient to wrap human mtDNA entirely. TFAM resolves D-loops in vitro if added in similar stoichiometries, mtSSB inhibits the resolution of mtDNA by TFAM but enhances resolution by RecG, a junction-specific helicase from Escherichia coli. Hence, mtSSB functions in both stabilization and resolution. We propose that TFAM and mSSB are cooperatively involved in stabilizing D-loops and in the maintenance of mtDNA.