Heterodimerization between members of the Nur subfamily of orphan nuclear receptors as a novel mechanism for gene activation.
We have recently shown that the orphan nuclear receptor Nur77 (NGFI-B) is most active in transcription when it is interacting with a cognate DNA sequence as a homodimer. Further, we have shown that the target for Nur77 dimers, the Nur response element (NurRE), is responsive to physiological stimuli in both endocrine and lymphoid cells, whereas other DNA targets of Nur77 action are not. The Nur77 subfamily also includes two related receptors, Nur-related factor 1 (Nurr1) and neuron-derived orphan receptor 1 (NOR-1). Often, more than one member of this subfamily is induced in response to extracellular signals. We now show that Nur77 and Nurr1 form heterodimers in vitro in the presence or absence of NurRE, and we have documented interactions between these proteins in vivo by using a two-hybrid system in mammalian cells. These heterodimers synergistically enhance transcription from NurRE reporters in comparison to that seen with homodimers. The naturally occurring NurRE from the pro-opiomelanocortin gene preferentially binds and activates transcription in the presence of Nur77 homo- or heterodimers, while a consensus NurRE sequence does not show this preference. Taken together, the data indicate that members of the Nur77 subfamily are most potent as heterodimers and that different dimers exhibit target sequence preference. Thus, we propose that a combinatorial code relying on specific NurRE sequences might be responsible for the activation of subsets of target genes by one of the members of the Nur77 subfamily of transcription factors.
Maira
M
M
Laboratoire de Génétique Moléculaire, Institut de Recherches Cliniques de Montréal, Montréal, Québec H2W 1R7, Canada.
Martens
C
C
Philips
A
A
Drouin
J
J
D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019281:Dimerization; D017930:Genes, Reporter; D008957:Models, Genetic; D009419:Nerve Tissue Proteins / Q000378:metabolism; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; D011333:Pro-Opiomelanocortin / Q000235:genetics*; D011485:Protein Binding; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D011987:Receptors, Steroid; D011988:Receptors, Thyroid Hormone; D020218:Response Elements; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D020798:Two-Hybrid System Techniques
D004268:DNA-Binding Proteins; C539821:NR4A1 protein, human; C539882:NR4A2 protein, human; C490412:NR4A3 protein, human; D009419:Nerve Tissue Proteins; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D011988:Receptors, Thyroid Hormone; D014157:Transcription Factors; D011333:Pro-Opiomelanocortin; D003346:Corticotropin-Releasing Hormone