Functional domains and phosphorylation of the orphan receptor Nur77

• Published in: Molecular endocrinology (Baltimore, Md.) Vol. 7; no. 8; p. 953
• Main Authors: Davis, I J, Hazel, T G, Chen, R H, Blenis, J, Lau, L F
• Format: Journal Article
• Language: English
• Published: United States 01-08-1993
• Subjects: 3T3 Cells; Animals; Base Sequence; Cercopithecus aethiops; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Gene Expression Regulation - drug effects; Ligands; Mice; Molecular Sequence Data; Nuclear Receptor Subfamily 4, Group A, Member 1; Phosphorylation; Protein Processing, Post-Translational; Protein Structure, Tertiary; Protein-Serine-Threonine Kinases - metabolism; Rats; Receptors, Cytoplasmic and Nuclear; Receptors, Glucocorticoid - genetics; Receptors, Steroid; Recombinant Fusion Proteins - metabolism; Ribosomal Protein S6 Kinases; Sequence Deletion; Transcription Factors - chemistry; Transcription Factors - genetics; Transcription Factors - metabolism; Transcriptional Activation
• ISSN: 0888-8809
• DOI: 10.1210/me.7.8.953

Nur77 represents a unique class within the steroid receptor superfamily since its synthesis is tightly regulated by extracellular signals and it is capable of potent transactivation activity in the absence of an exogenously added ligand. In this study, we sought to dissect the functional domains regulating the activities of Nur77 by deletion mapping. We demonstrate that whereas the transactivation activity of Nur77 resides in the amino-terminal domain, the carboxy-terminal domain regulates this activity. A short deletion from the carboxy terminus eliminates transactivation activity while a further deletion restores the activity. Deletion of the domain immediately carboxyl to the zinc fingers motif eliminates both DNA binding activity and nuclear localization, thus abolishing transactivation. Nur77 is posttranslationally modified predominantly by phosphorylation, which occurs primarily at the N-terminal domain. The growth-related kinase pp90rsk, but neither the pp44mapk nor the pp70s6k, can phosphorylate recombinant Nur77 in vitro. Furthermore, we have identified a site within the region required for sequence-specific DNA binding, Ser-354, that is phosphorylated by pp90rsk in vitro; this site is also phosphorylated in vivo. The possibility that phosphorylation might affect DNA binding is discussed.