Structure-function analysis reveals the molecular determinants of the impaired biological function of DAX-1 mutants in AHC patients.
Mutations in the DAX-1 (NR0B1) gene cause the X-linked form of adrenal hypoplasia congenita (AHC), which is constantly found associated with hypogonadotropic hypogonadism (HHG). DAX-1 encodes an atypical orphan member of the nuclear hormone receptor superfamily. DAX-1 acts at multiple levels to repress the expression of genes involved in steroid hormone metabolism through a potent transcriptional repression domain present in its C-terminus, which is similar to the nuclear receptors' ligand binding domain. All DAX-1 mutations causing AHC/HHG alter the protein C-terminal domain, impairing its nuclear localization and, consequently, its transcriptional repression activity. Here we show that DAX-1 AHC mutants have a misfolded conformation, which correlates with their cytoplasmic retention. Extensive structure-function analysis reveals that the chemical nature of amino acid residues at positions interested by AHC mutations and critical determinants in helix 12 affect DAX-1 nuclear localization and transcriptional silencing. Surprisingly, mutations in a conserved putative corepressor binding surface have a negative effect upon DAX-1 transcriptional repression only when they also affect protein expression levels. These data suggest that a folding defect underlies the impaired function of DAX-1 missense mutants found in AHC/HHG patients and that interactions with transcriptional cofactors different from known corepressors mediate DAX-1 silencing properties.
Lehmann
Sylvia G
SG
Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Université Louis Pasteur, BP 163, 67404 Illkirch, Strasbourg, France.
Wurtz
Jean-Marie
JM
Renaud
Jean-Paul
JP
Sassone-Corsi
Paolo
P
Lalli
Enzo
E
D000312:Adrenal Hyperplasia, Congenital / Q000235:genetics* / Q000378:metabolism; D019943:Amino Acid Substitution; D057137:DAX-1 Orphan Nuclear Receptor; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D010750:Phosphoproteins / Q000235:genetics; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D018168:Receptors, Retinoic Acid / Q000235:genetics* / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D013329:Structure-Activity Relationship; D000098682:Steroidogenic Acute Regulatory Protein
D057137:DAX-1 Orphan Nuclear Receptor; D004268:DNA-Binding Proteins; C539965:NR0B1 protein, human; D010750:Phosphoproteins; D018168:Receptors, Retinoic Acid; D012097:Repressor Proteins; D000098682:Steroidogenic Acute Regulatory Protein