Activation of the human mitochondrial transcription factor A gene by nuclear respiratory factors: a potential regulatory link between nuclear and mitochondrial gene expression in organelle biogenesis.
Mitochondrial transcription factor A (mtTFA), the product of a nuclear gene, stimulates transcription from the two divergent mitochondrial promoters and is likely the principal activator of mitochondrial gene expression in vertebrates. Here we establish that the proximal promoter of the human mtTFA gene is highly dependent upon recognition sites for the nuclear respiratory factors, NRF-1 and NRF-2, for activity. These factors have been previously implicated in the activation of numerous nuclear genes that contribute to mitochondrial respiratory function. The affinity-purified factors from HeLa cells specifically bind to the mtTFA NRF-1 and NRF-2 sites through guanine nucleotide contacts that are characteristic for each site. Mutations in these contacts eliminate NRF-1 and NRF-2 binding and also dramatically reduce promoter activity in transfected cells. Although both factors contribute, NRF-1 binding appears to be the major determinant of promoter function. This dependence on NRF-1 activation is confirmed by in vitro transcription using highly purified recombinant proteins that display the same binding specificities as the HeLa cell factors. The activation of the mtTFA promoter by both NRF-1 and NRF-2 therefore provides a link between the expression of nuclear and mitochondrial genes and suggests a mechanism for their coordinate regulation during organelle biogenesis.
Virbasius
J V
JV
Department of Cell, Molecular and Structural Biology, Northwestern University Medical School, Chicago, IL 60611.
Scarpulla
R C
RC
D001483:Base Sequence; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000378:metabolism*; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis / Q000235:genetics; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D051268:GA-Binding Protein Transcription Factor; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D051265:NF-E2-Related Factor 1; D009687:Nuclear Proteins; D051266:Nuclear Respiratory Factor 1; D051264:Nuclear Respiratory Factors; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*
D004268:DNA-Binding Proteins; D051268:GA-Binding Protein Transcription Factor; D024101:Mitochondrial Proteins; D051265:NF-E2-Related Factor 1; C495633:NRF1 protein, human; D009687:Nuclear Proteins; D051266:Nuclear Respiratory Factor 1; D051264:Nuclear Respiratory Factors; D011993:Recombinant Fusion Proteins; C499631:TFAM protein, human; D015534:Trans-Activators; D014157:Transcription Factors; C422562:mitochondrial transcription factor A; D015500:Chloramphenicol O-Acetyltransferase