Isoform-specific amino-terminal domains dictate DNA-binding properties of ROR alpha, a novel family of orphan hormone nuclear receptors.

Abstract

Three isoforms of a novel member of the steroid hormone nuclear receptor superfamily related to the retinoic acid receptors have been identified. The three isoforms, referred to as RORal, R0Ra2, and R0Ra3, share common DNA-and putative ligand-binding domains but are characterized by distinct amino-terminal domains generated by alternative RNA processing. An exon encoding a functionally important subregion of the amino-terminal domain of the RORa2 isoform resides on the opposite strand of a cytochrome c-processed pseudogene. Binding site selection using in vitro-synthesized proteins reveals that the RORal and R0Ra2 isoforms bind DNA as monomers to hormone response elements composed of a 6-bp AT-rich sequence preceding a half-site core motif PuGGTCA (RORE). However, RORal and RORa2 display different binding specificities: RORal binds to and constitutively activates transcription from a large subset of ROREs, whereas R0Ra2 recognizes ROREs with strict specificity and displays weaker transcriptional activity. The differential DNA-binding activity of each isoform maps to their respective amino-terminal domains. Whereas truncation of the amino-terminal domain diminishes the ability of RORal to bind DNA, a similar deletion relaxes RORa2-binding specificity to that displayed by RORal. Remarkably, transfer of the entire amino-terminal region of RORal or amino-terminal deletion of RORa2 confers RORE-binding specificities to het^erologous receptors. These results demonstrate that the amino-terminal domain and the zinc finger region work in concert to confer high affinity and specific DNA-binding properties to the ROR isoforms and suggest a novel strategy to control DNA-binding activity of nuclear receptors.

The Orphan Receptor Hepatic Nuclear Factor 4 Functions as a Transcriptional Activator for Tissue-Specific and Hypoxia-Specific Erythropoietin Gene Expression and Is Antagonized by EAR3/COUP-TF1

“…As a result, HNF-4⌬C is 356 amino acids long. Plasmids expressing EAR3/COUP-TF1 (33), ROR␣1 (14), and other orphan receptors were prepared in a similar way by inserting their cDNAs into pCMX.…”

Rorα, a pivotal nuclear receptor for Purkinje neuron survival and differentiation: From development to ageing

“…These isoforms differ in their N-terminal modulator region, which interacts with A/T-rich sequences of the RORE and thus permits distinct promoter recognition and transactivation properties through an identical DNA binding domain (DBD) (9,14). Functionally active RORE have been identified in a number of putative target genes, but the functional regulation by RORα in vivo remains to be demonstrated for many of them.…”

“…By a combination of promoter usage and alternative splicing, the Rora gene gives rise to four isoforms in human, RORα1, α2, α3 and RORα4 (also termed RZRα), while only α1 and α4 isoforms have been detected in the mouse (14)(15)(16). These isoforms differ in their N-terminal modulator region, which interacts with A/T-rich sequences of the RORE and thus permits distinct promoter recognition and transactivation properties through an identical DNA binding domain (DBD) (9,14).…”

Transcriptional profiling reveals a role for RORα in regulating gene expression in obesity-associated inflammation and hepatic steatosis

“…It is now well recognized that obesity is associated with chronic low-grade inflammation and that inflammatory processes play an important role in obesity and related pathologies (18,44,53). Infiltration of macrophages and various T-lymphocytes in hypertrophic adipose tissues have been considered as important early events in the development of obesity-associated complications (14, 38, 57) and the release of proinflammatory cytokines by adipose tissue plays a key role in the development of insulin resistance, NAFDL, and cardiovascular disease.Retinoid-related orphan receptors ROR␣, ␤, and ␥ (NR1F1-3) constitute a subfamily of nuclear receptors that regulate gene transcription by binding as a monomer to ROR-response elements (RORE) in the regulatory region of target genes (15,20,35). Recent studies have demonstrated that RORs function as ligand-dependent transcription factors (20,23,30,48,55).…”

“…Retinoid-related orphan receptors ROR␣, ␤, and ␥ (NR1F1-3) constitute a subfamily of nuclear receptors that regulate gene transcription by binding as a monomer to ROR-response elements (RORE) in the regulatory region of target genes (15,20,35). Recent studies have demonstrated that RORs function as ligand-dependent transcription factors (20,23,30,48,55).…”