title: Expression and function of nuclear receptor co-activator 4: evidence of a potential role independent of co-activator activity.
abstract: Nuclear receptor coactivator 4 (NcoA4), also known as androgen receptor-associated protein 70 (ARA70), was initially discovered as a component of Ret-Fused Gene expressed in a subset of papillary thyroid carcinomas. Subsequent studies have established NcoA4 as a coactivator for a variety of nuclear receptors, including peroxisome proliferator activated receptors α and γ, and receptors for steroid hormones, vitamins D and A, thyroid hormone, and aryl hydrocarbons. While human NcoA4 has both LXXLL and FXXLF motifs that mediate p160 coactivator nuclear receptor interactions, this ubiquitously expressed protein lacks clearly defined functional domains. Several studies indicate that NcoA4 localizes predominantly to the cytoplasm and affects ligand-binding specificity of the androgen receptor, which has important implications for androgen-independent prostate cancer. Two NcoA4 variants, which may exert differential activities, have been identified in humans. Recent studies suggest that NcoA4 may play a role in development, carcinogenesis, inflammation, erythrogenesis, and cell cycle progression that may be independent of its role as a receptor coactivator. This review summarizes what is currently known of the structure, expression, regulation, and potential functions of this unique protein in cancerous and non-cancerous pathologies.
authors.affiliation: Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 25 Orde Street, 6-1001TB, Toronto, ON, M5T 3H7, Canada.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Kollara
authors.forename: Theodore J
authors.initials: TJ
authors.lastname: Brown
mesh_terms: D020869:Gene Expression Profiling; D020022:Genetic Predisposition to Disease; D006801:Humans; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism; D056918:Nuclear Receptor Coactivators / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics* / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism
chemical_list: C410798:AR protein, human; C111382:NCOA4 protein, human; D056918:Nuclear Receptor Coactivators; D011944:Receptors, Androgen; D018160:Receptors, Cytoplasmic and Nuclear; D015534:Trans-Activators