Tissue- and nuclear receptor-specific function of the C-terminal LXXLL motif of coactivator NCoA6/AIB3 in mice

Mol Cell Biol. 2007 Dec;27(23):8073-86. doi: 10.1128/MCB.00451-07. Epub 2007 Oct 1.


Although the LXXLL motif of nuclear receptor (NR) coactivators is essential for interaction with NRs, its role has not been assessed in unbiased animal models. The nuclear receptor coactivator 6 (NCoA6; also AIB3, PRIP, ASC-2, TRBP, RAP250, or NRC) is a coactivator containing an N-terminal LXXLL-1 (L1) and a C-terminal L2. L1 interacts with many NRs, while L2 interacts with the liver X receptor alpha (LXRalpha) and the estrogen receptor alpha (ERalpha). We generated mice in which L2 was mutated into AXXAL (L2m) to disrupt its interaction with LXRalpha and ERalpha. NCoA6(L2m/L2m) mice exhibited normal reproduction, mammary gland morphogenesis, and ERalpha target gene expression. In contrast, when treated with an LXRalpha agonist, lipogenesis and the LXRalpha target gene expression were significantly reduced in NCoA6(L2m/L2m) mice. The induction of Cyp7A1 expression by a high-cholesterol diet was impaired in NCoA6(L2m/L2m) mice, which reduced bile acid synthesis in the liver and excretion in the feces and resulted in cholesterol accumulation in the liver and blood. These results demonstrate that L2 plays a tissue- and NR-specific role: it is required for NCoA6 to mediate LXRalpha-regulated lipogenesis and cholesterol/bile acid homeostasis in the liver but not required for ERalpha function in the mammary gland.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Motifs
  • Animals
  • Bile Acids and Salts / metabolism
  • Cholesterol 7-alpha-Hydroxylase / biosynthesis
  • Cholesterol, Dietary / pharmacology
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Enzyme Induction / drug effects
  • Estrogen Receptor alpha / metabolism*
  • Feces
  • Gene Expression Regulation / drug effects
  • Hypercholesterolemia
  • Intracellular Signaling Peptides and Proteins / chemistry*
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Lipogenesis / drug effects
  • Liver / drug effects
  • Liver / enzymology
  • Liver / metabolism
  • Liver X Receptors
  • Male
  • Mammary Glands, Animal / drug effects
  • Mammary Glands, Animal / embryology
  • Mice
  • Mice, Mutant Strains
  • Morphogenesis / drug effects
  • Mutation / genetics
  • Nuclear Receptor Coactivators
  • Organ Specificity / drug effects
  • Orphan Nuclear Receptors
  • Receptors, Cytoplasmic and Nuclear / genetics
  • Receptors, Cytoplasmic and Nuclear / metabolism*
  • Reproduction / drug effects
  • Steroids / pharmacology
  • Survival Analysis
  • Transcription, Genetic / drug effects


  • Bile Acids and Salts
  • Cholesterol, Dietary
  • DNA-Binding Proteins
  • Estrogen Receptor alpha
  • Intracellular Signaling Peptides and Proteins
  • Liver X Receptors
  • Ncoa6 protein, mouse
  • Nr1h3 protein, mouse
  • Nuclear Receptor Coactivators
  • Orphan Nuclear Receptors
  • Receptors, Cytoplasmic and Nuclear
  • Steroids
  • Cholesterol 7-alpha-Hydroxylase
  • Cyp7a1 protein, mouse