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Mol. Cell. Biol., 10 1996, 5708-5716, Vol 16, No. 10
S Gugneja, CM Virbasius and RC Scarpulla
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.
Copyright © 1996, American Society for Microbiology
Nuclear respiratory factors 1 and 2 utilize similar glutamine- containing clusters of hydrophobic residues to activate transcription
Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611, USA.
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