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XB-ART-18976
Mol Cell Biol 1995 Dec 01;1512:7032-42. doi: 10.1128/MCB.15.12.7032.
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Distinct roles for two purified factors in transcription of Xenopus mitochondrial DNA.

Antoshechkin I , Bogenhagen DF .


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Transcription of Xenopus laevis mitochondrial DNA (xl-mtDNA) by the mitochondrial RNA polymerase requires a dissociable factor. This factor was purified to near homogeneity and identified as a 40-kDa protein. A second protein implicated in the transcription of mtDNA, the Xenopus homolog of the HMG box protein mtTFA, was also purified to homogeneity and partially sequenced. The sequence of a cDNA clone encoding xl-mtTFA revealed a high degree of sequence similarity to human and Saccharomyces cerevisiae mtTFA. xl-mtTFA was not required for basal transcription from a minimal mtDNA promoter, and this HMG box factor could not substitute for the basal factor, which is therefore designated xl-mtTFB. An antibody directed against the N terminus of xl-mtTFA did not cross-react with xl-mtTFB. xl-mtTFA is an abundant protein that appears to have at least two functions in mitochondria. First, it plays a major role in packaging mtDNA within the organelle. Second, DNase I footprinting experiments identified preferred binding sites for xl-mtTFA within the control region of mtDNA next to major mitochondrial promoters. We show that binding of xl-mtTFA to a site separating the two clusters of bidirectional promoters selectively stimulates specific transcription in vitro by the basal transcription machinery, comprising mitochondrial RNA polymerase and xl-mtTFB.

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Species referenced: Xenopus laevis
Genes referenced: tfam

References [+] :
Bogenhagen, Purification of Xenopus laevis mitochondrial RNA polymerase and identification of a dissociable factor required for specific transcription. 1988, Pubmed, Xenbase