Nuclear orphan receptors regulate transcription of the gene for the human luteinizing hormone receptor.
An imperfect estrogen receptor half-site response element direct-repeat, located within the TATA-less promoter of the human luteinizing hormone receptor (hLHR), was identified as an inhibitory site for Sp1/Sp3-driven basal transcription. Isolation of proteins recognizing this site by yeast one-hybrid screening of a human placenta cDNA library revealed three nuclear orphan receptors, EAR2, EAR3/COUP-TFI, and TR4. Electrophoresis mobility shift assays demonstrated that the in vitro translated nuclear orphan receptors specifically bound the direct-repeat motif of the hLHR promoter. Also, endogenous EAR2 and EAR3/COUP-TFI from JAR cell and human testis and TR4 from testes bound this motif in electrophoresis mobility shift assays. Functional analyses in CV-1 cells showed that EAR2 and EAR3/COUP-TFI repressed the hLHR promoter activity by up to 70% in a dose-dependent and sequence-specific manner. Conversely, TR4 activated the hLHR promoter activity up to 2.5-fold through binding to the same cis-element. The stimulation was reversed by coexpression of EAR2 or EAR3/COUP-TFI, indicating their competitive binding for this site. Such recognition of a common cognate site by the proteins with antagonistic functions implies that a net regulation of the hLHR gene may result from the relative availability of repressors and activator in a physiological state. This also may contribute to the differential expression of the hLHR gene in gonadal and non-gonadal tissues.[1]References
- Nuclear orphan receptors regulate transcription of the gene for the human luteinizing hormone receptor. Zhang, Y., Dufau, M.L. J. Biol. Chem. (2000) [Pubmed]
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