Identification of a novel testicular orphan receptor-4 (TR4)-associated protein as repressor for the selective suppression of TR4-mediated transactivation.
Although many co-activators have been identified for various nuclear receptors, relatively fewer co-repressors have been isolated and characterized. Here we report the identification of a novel testicular orphan nuclear receptor-4 (TR4)-associated protein (TRA16) that is mainly localized in the nucleus of cells as a repressor to suppress TR4-mediated transactivation. The suppression of TR4-mediated transactivation is selective because TRA16 shows only a slight influence on the transactivation of androgen receptor, glucocorticoid receptor, and progesterone receptor. Sequence analysis shows that TRA16 is a novel gene with 139 amino acids in an open reading frame with a molecular mass of 16 kDa, which did not match any published gene sequences. Mammalian two-hybrid system and co-immunoprecipitation assays both demonstrate that TRA16 can interact strongly with TR4. The electrophoretic mobility shift assay suggests that TRA16 may suppress TR4-mediated transactivation via decreased binding between the TR4 protein and the TR4 response element on the target gene(s). Furthermore, TRA16 can also block the interaction between TR4 and TR4 ligand-binding domain through interacting with TR4-DNA-binding and ligand-binding domains. These unique suppression mechanisms suggest that TRA16 may function as a novel repressor to selectively suppress the TR4-mediated transactivation.
Pubmed ID: 12486131 RIS Download
Amino Acid Sequence | Animals | Base Sequence | Blotting, Northern | COS Cells | Cell Nucleus | Cells, Cultured | DNA, Complementary | Gene Library | Genes, Reporter | Humans | Immunohistochemistry | Male | Mice | Microscopy, Fluorescence | Molecular Sequence Data | Nuclear Proteins | Protein Binding | Protein Structure, Tertiary | RNA, Messenger | Receptors, Androgen | Receptors, Glucocorticoid | Receptors, Progesterone | Receptors, Steroid | Receptors, Thyroid Hormone | Repressor Proteins | Testis | Tissue Distribution | Transcriptional Activation | Transfection | Two-Hybrid System Techniques