Nuclear respiratory factors 1 and 2 utilize similar glutamine-containing clusters of hydrophobic residues to activate transcription.
Nuclear respiratory factors 1 and 2 (NRF-1 and NRF-2) are ubiquitous transcription factors that have been implicated in the control of nuclear genes required for respiration, heme biosynthesis, and mitochondrial DNA transcription and replication. Recently, both factors have been found to be major transcriptional determinants for a subset of these genes that define a class of simple promoters involved in respiratory chain expression. Here, functional domains required for transactivation by NRF-1 have been defined. An atypical nuclear localization signal resides in a conserved amino-terminal region adjacent to the DNA binding domain and consists of functionally redundant clusters of basic residues. A second domain in the carboxy-terminal half of the molecule is necessary for transcriptional activation. The activation domains of both NRF-1 and NRF-2 were extensively characterized by both deletion and alanine substitution mutagenesis. The results show that these domains do not fall into known classes defined by a preponderance of amino acid residues, including glutamines, prolines, or isoleucines, as found in other eukaryotic activators. Rather, in both factors, a series of tandemly arranged clusters of hydrophobic amino acids were required for activation. Although all of the functional clusters contain glutamines, the glutamines differ from the hydrophobic residues in that they are inconsequential for activation. Unlike the NRF-2 domain, which contains its essential hydrophobic motifs within 40 residues, the NRF-1 domain spans about 40% of the molecule and appears to have a bipartite structure. The findings indicate that NRF-1 and NRF-2 utilize similar hydrophobic structural motifs for activating transcription.
Gugneja
S
S
Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611, USA.
Virbasius
C M
CM
Scarpulla
R C
RC
D000409:Alanine; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D017931:DNA Primers; D004272:DNA, Mitochondrial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005656:Fungal Proteins; D005973:Glutamine; D006418:Heme / Q000096:biosynthesis; D016350:Leucine Zippers; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D051265:NF-E2-Related Factor 1; D051267:NF-E2-Related Factor 2; D051264:Nuclear Respiratory Factors; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins; D012119:Respiration; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
D017931:DNA Primers; D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D051265:NF-E2-Related Factor 1; D051267:NF-E2-Related Factor 2; D051264:Nuclear Respiratory Factors; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D005973:Glutamine; D006418:Heme; D000409:Alanine