title: Dosage-sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome, gene 1 (DAX1) (NR0B1) and small heterodimer partner (SHP) (NR0B2) form homodimers individually, as well as DAX1-SHP heterodimers.
abstract: Dosage-sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome, gene 1 (DAX1) (NR0B1), and small heterodimer partner (SHP) (NR0B2) are atypical nuclear receptor superfamily members that function primarily as corepressors through heterodimeric interactions with other nuclear receptors. Mutations in DAX1 cause adrenal hypoplasia congenita, and mutations in SHP lead to mild obesity and insulin resistance, but the mechanisms are unclear. We investigated the existence and subcellular localization of DAX1 and SHP homodimers and the dynamics of homodimerization. We demonstrated DAX1 homodimerization in the nucleus and cytoplasm, and dissociation of DAX1 homodimers upon heterodimerization with steroidogenic factor 1 (SF1) or ligand-activated estrogen receptor-alpha (ERalpha). DAX1 homodimerization involved an interaction between its amino and carboxy termini involving its LXXLL motifs and activation function (AF)-2 domain. We observed SHP homodimerization in the nucleus of mammalian cells and showed dissociation of SHP homodimers upon heterodimerization with ligand-activated ERalpha. We observed DAX1-SHP heterodimerization in the nucleus of mammalian cells and demonstrated the involvement of the LXXLL motifs and AF-2 domain of DAX1 in this interaction. We further demonstrate heterodimerization of DAX1 with its alternatively spliced isoform, DAX1A. This is the first evidence of homodimerization of individual members of the unusual NR0B nuclear receptor family and heterodimerization between its members. Our results suggest that DAX1 forms antiparallel homodimers through the LXXLL motifs and AF-2 domain. These homodimers may function as holding reservoirs in the absence of heterodimeric partners. The formation of DAX1 and SHP homodimers and DAX1-SHP and DAX1-DAX1A heterodimers suggests the possibility of novel functions independent of their coregulator roles, suggesting additional complexity in the molecular mechanisms of DAX1 and SHP action.
authors.affiliation: Department of Human Genetics, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California 90095-1752, USA.
authors.forename: Anita K
authors.initials: AK
authors.lastname: Iyer
authors.forename: Yao-Hua
authors.initials: YH
authors.lastname: Zhang
authors.forename: Edward R B
authors.initials: ER
authors.lastname: McCabe
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D015153:Blotting, Western; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D057137:DAX-1 Orphan Nuclear Receptor; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019281:Dimerization; D047628:Estrogen Receptor alpha / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D054339:Steroidogenic Factor 1; D020798:Two-Hybrid System Techniques
chemical_list: D057137:DAX-1 Orphan Nuclear Receptor; D004268:DNA-Binding Proteins; D047628:Estrogen Receptor alpha; C539965:NR0B1 protein, human; C515057:NR5A1 protein, human; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D012097:Repressor Proteins; D054339:Steroidogenic Factor 1; C099713:nuclear receptor subfamily 0, group B, member 2