The C-terminal tail of mitochondrial transcription factor a markedly strengthens its general binding to DNA.
Mitochondrial transcription factor A (TFAM) contains a basic C-terminal tail which is essential for the promoter-specific transcription. TFAM is also a major component of a protein-mitochondrial DNA (mtDNA) complex, called nucleoid, as a non-specific DNA-binding protein. However, little is known about a role of the C-tail in the nucleoid. Overexpression of full-length TFAM decreased the amount of a D-loop form of mtDNA in cells, while overexpression of TFAM lacking its C-tail (TFAM-DeltaC) did not, suggesting that the C-tail is involved in destabilization or formation of the D-loop. An mRNA for mtDNA-derived ND1 was hardly decreased in the former but rather decreased in the latter. Given that the D-loop formation is coupled with the transcription, the decrease in the D-loop is likely due to its destabilization. The recombinant full-length TFAM much strongly unwound DNA than TFAM-DeltaC, which is consistent with the above idea because D-loop is resolved by unwinding of the supercoiling state. Notably, truncation of the C-tail decreased DNA-binding activity of TFAM by three orders of magnitude. Thus, the C-terminal tail of TFAM is important for the strong general binding to mtDNA. This strong DNA-binding conferred by the C-tail may play an important role in the nucleoid structure.
Ohgaki
Kippei
K
Department of Clinical Chemistry and Laboratory Medicine, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan.
Kanki
Tomotake
T
Fukuoh
Atsushi
A
Kurisaki
Hironori
H
Aoki
Yoshimasa
Y
Ikeuchi
Masaki
M
Kim
Sang Ho
SH
Hamasaki
Naotaka
N
Kang
Dongchon
D
D004272:DNA, Mitochondrial / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic
D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D024101:Mitochondrial Proteins; C499631:TFAM protein, human; D014157:Transcription Factors