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キーワード:
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要旨:
The mitochondrial genome is transcribed by a single-subunit T7 phage-like RNA polymerase (mtRNAP), structurally unrelated to cellular RNAPs.
In higher eukaryotes, mtRNAP requires two transcription factors for efficient initiation—TFAM, a
major nucleoid protein, and TFB2M, a transient
component of mtRNAP catalytic site. The mechanisms
behind assembly of the mitochondrial transcription
machinery and its regulation are poorly
understood. We isolated and identified a previously
unknown human mitochondrial transcription intermediate—
a pre-initiation complex that includes
mtRNAP, TFAM and promoter DNA. Using protein–
protein cross-linking, we demonstrate that human
TFAM binds to the N-terminal domain of mtRNAP,
which results in bending of the promoter DNA
around mtRNAP. The subsequent recruitment of
TFB2M induces promoter melting and formation of
an open initiation complex. Our data indicate that
the pre-initiation complex is likely to be an important
target for transcription regulation and provide
basis for further structural, biochemical and biophysical
studies of mitochondrial transcription.
