Family

Orphan nuclear receptor, NOR1 type (IPR003072)

Short name: NOR1_rcpt

Family relationships

Description

Steroid or nuclear hormone receptors (4A nuclear receptor, NRs) constitute an important superfamily of transcription regulators that are involved in widely diverse physiological functions, including control of embryonic development, cell differentiation and homeostasis. Members of the superfamily include the steroid hormone receptors and receptors for thyroid hormone, retinoids, 1,25-dihydroxy-vitamin D3 and a variety of other ligands [PMID: 14747695]. The proteins function as dimeric molecules in nuclei to regulate the transcription of target genes in a ligand-responsive manner [PMID: 7899080, PMID: 8165128]. In addition to C-terminal ligand-binding domains, these nuclear receptors contain a highly-conserved, N-terminal zinc-finger that mediates specific binding to target DNA sequences, termed ligand-responsive elements. In the absence of ligand, steroid hormone receptors are thought to be weakly associated with nuclear components; hormone binding greatly increases receptor affinity.

NRs are extremely important in medical research, a large number of them being implicated in diseases such as cancer, diabetes, hormone resistance syndromes, etc. While several NRs act as ligand-inducible transcription factors, many do not yet have a defined ligand and are accordingly termed 'orphan' receptors. During the last decade, more than 300 NRs have been described, many of which are orphans, which cannot easily be named due to current nomenclature confusions in the literature. However, a new system has recently been introduced in an attempt to rationalise the increasingly complex set of names used to describe superfamily members.

Human NOR-1 mRNA has been detected in adult heart and skeletal muscle, as well as in foetal brain, indicating that its expression is not restricted to events that occur during neural development [PMID: 8809112]. It has been shown that in a skeletal myxoid chondrosarcoma, the EWS gene becomes fused to NOR1 [PMID: 8570200]. The chimaeric EWS-NOR gene encodes a EWS-NOR fusion protein in which the C-terminal RNA-binding domain of EWS is replaced by the entire NOR protein, comprising a long N-terminal domain, a central DNA binding domain and a C-terminal ligand-binding/dimerisation domain [PMID: 8570200].

GO terms

Biological Process

GO:0006355 regulation of transcription, DNA-templated

Molecular Function

GO:0003677 DNA binding
GO:0004879 RNA polymerase II transcription factor activity, ligand-activated sequence-specific DNA binding

Cellular Component

GO:0005634 nucleus

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PRINTS