A human mitochondrial transcription factor is related to RNA adenine methyltransferases and binds S-adenosylmethionine.
A critical step toward understanding mitochondrial genetics and its impact on human disease is to identify and characterize the full complement of nucleus-encoded factors required for mitochondrial gene expression and mitochondrial DNA (mtDNA) replication. Two factors required for transcription initiation from a human mitochondrial promoter are h-mtRNA polymerase and the DNA binding transcription factor, h-mtTFA. However, based on studies in model systems, the existence of a second human mitochondrial transcription factor has been postulated. Here we report the isolation of a cDNA encoding h-mtTFB, the human homolog of Saccharomyces cerevisiae mitochondrial transcription factor B (sc-mtTFB) and the first metazoan member of this class of transcription factors to which a gene has been assigned. Recombinant h-mtTFB is capable of binding mtDNA in a non-sequence-specific fashion and activates transcription from the human mitochondrial light-strand promoter in the presence of h-mtTFA in vitro. Remarkably, h-mtTFB and its fungal homologs are related in primary sequence to a superfamily of N6 adenine RNA methyltransferases. This observation, coupled with the ability of recombinant h-mtTFB to bind S-adenosylmethionine in vitro, suggests that a structural, and perhaps functional, relationship exists between this class of transcription factors and this family of RNA modification enzymes and that h-mtTFB may perform dual functions during mitochondrial gene expression.
McCulloch
Vicki
V
Department of Biochemistry, Rollins Research Center, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Seidel-Rogol
Bonnie L
BL
Shadel
Gerald S
GS
D000595:Amino Acid Sequence; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000737:chemistry / Q000502:physiology*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D008164:Luminescent Proteins; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C499631:TFAM protein, human; C499632:TFB1M protein, human; D014157:Transcription Factors; C422562:mitochondrial transcription factor A; D049452:Green Fluorescent Proteins; D012436:S-Adenosylmethionine; D008780:Methyltransferases