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Mol. Cell. Biol., Mar 1997, 1476-1483, Vol 17, No. 3
M Ito, R Yu and JL Jameson
X-linked adrenal hypoplasia congenita (AHC) with hypogonadotropic
hypogonadism was recently shown to be caused by mutations in a gene
referred to as DAX-1, which encodes a novel member of the orphan nuclear
receptor family. DAX-1 is homologous to other nuclear receptors in its
carboxy-terminal region, but it lacks the characteristic zinc finger
DNA-binding domain. The tissue distribution of DAX-1 (adrenal cortex,
gonads, hypothalamus, and pituitary) is the same as that of another orphan
nuclear receptor, steroidogenic factor 1 (SF-1), that is required for
development of the adrenal glands and gonads. We examined whether DAX-1 and
SF-1 might interact in the regulation of SF-1- responsive target genes.
Coexpression of DAX-1 and SF-1 inhibited SF-1- mediated transactivation.
DAX-1 was shown to interact directly with SF- 1 in in vitro protein binding
studies; however, it did not interfere with SF-1 binding to DNA in gel
mobility shift assays. Transactivation by GAL4-SF-1 constructs was
inhibited by DAX-1, indicating that neither the SF-1 DNA-binding domain nor
the SF-1 binding sites are required for inhibition by DAX-1. A series of
DAX-1 deletion mutants localized the inhibitory domain to the
carboxy-terminal region of the protein. Deletion of this domain also
reduced basal transcriptional silencing by GAL4-DAX-1. This inhibitory
domain has been deleted in all naturally occurring AHC deletion mutants
described to date. In addition, two naturally occurring point mutations in
DAX-1 exhibited impaired inhibition of SF-1. We conclude that DAX-1 can
inhibit SF-1 transcriptional activity and suggest that the loss of this
inhibitory property in DAX-1 may account in part for the phenotype of AHC.
Copyright © 1997, American Society for Microbiology
DAX-1 inhibits SF-1-mediated transactivation via a carboxy-terminal domain that is deleted in adrenal hypoplasia congenita
Division of Endocrinology, Metabolism, and Molecular Medicine, Northwestern University Medical School, Chicago, Illinois 60611, USA.
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