Pregnane and Xenobiotic Receptor gene expression in liver cells is modulated by Ets-1 in synchrony with transcription factors Pax5, LEF-1 and c-Jun
Résumé
Nuclear receptor PXR is predominantly expressed in liver and intestine. Expression of PXR is observed to be dysregulated in various metabolic disorders indicating its involvement in disease development. However, information available on mechanisms of PXR self-regulation is fragmentary. The present investigation identifies some of the regulatory elements responsible for its tight regulation and low cellular expression. Here, we report that the PXR-promoter is a target for some key transcription factors like PU.1/Ets-1, Pax5, LEF-1 and c-Jun. Interestingly, we observed that PXR-promoter responsiveness to Pax5, LEF-1 and c-Jun, is considerably enhanced by Ets transcription factors (PU.1 and Ets-1). Co-transfection of cells with Ets-1, LEF-1 and c-Jun increased PXR-promoter activity by 5-fold and also induced expression of endogenous human PXR. Site-directed mutagenesis and transfection studies revealed that two Ets binding sites and two of the three LEF binding sites in the PXR-promoter are functional and have a positive effect on PXR transcription. Results suggest that expression of Ets family members, in conjunction with Pax5, LEF-1 and c-Jun, lead to coordinated up-regulation of PXR gene transcription. Insights obtained on the regulation of PXR gene have relevance in offering important cues towards normal functioning as well as development of several metabolic disorders via PXR signaling.
Mots clés
Promoter Regions
Genetic
Humans
Transcriptional Activation
Gene regulation
Liver
Trans-Activators
Gene Expression Regulation
Promoter-reporter assays
Hep G2 Cells
Lymphoid Enhancer-Binding Factor 1
cis-elements
PAX5 Transcription Factor
Receptors
Steroid
RNA Interference
Protein Binding
JNK Mitogen-Activated Protein Kinases
Pregnane and Xenobiotic Receptor
Transcription
Electrophoretic Mobility Shift Assay
Proto-Oncogene Proteins
RNA
Small Interfering
Transcription Factors
Proto-Oncogene Protein c-ets-1
Binding Sites