Regulation of mitochondrial D-loops by transcription factor A and single-stranded DNA-binding protein.
During replication, mitochondrial DNA (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 than 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 mtSSB are cooperatively involved in stabilizing D-loops and in the maintenance of mtDNA.
Takamatsu
Chihiro
C
Department of Clinical Chemistry and Laboratory Medicine, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan.
Umeda
Shuyo
S
Ohsato
Takashi
T
Ohno
Tetsuji
T
Abe
Yoshito
Y
Fukuoh
Atsushi
A
Shinagawa
Hideo
H
Hamasaki
Naotaka
N
Kang
Dongchon
D
D002460:Cell Line; D004272:DNA, Mitochondrial / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli; D029968:Escherichia coli Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; D009690:Nucleic Acid Conformation; D015534:Trans-Activators; D014157:Transcription Factors / Q000378:metabolism*; D029867:Xenopus Proteins
D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; C499631:TFAM protein, human; D015534:Trans-Activators; D014157:Transcription Factors; C097078:XL-MTTFA protein, Xenopus; D029867:Xenopus Proteins; C422562:mitochondrial transcription factor A; C071446:RecG protein, E coli