title: Transcription regulation of nuclear receptor PXR: Role of SUMO-1 modification and NDSM in receptor function.
abstract: Pregnane & Xenobiotic Receptor (PXR) is one of the 48 members of the nuclear receptor superfamily of ligand-modulated transcription factors. PXR plays an important role in metabolism and elimination of diverse noxious endobiotics and xenobiotics. Like in case of some nuclear receptors its function may also be differentially altered, positively or negatively, by various post-translational modifications. In this context, regulation of PXR function by SUMOylation is the subject of present investigation. Here, we report that human PXR is modiﬁed by SUMO-1 resulting in its enhanced transcriptional activity. RT-PCR analysis showed that PXR SUMOylation in presence of rifampicin also enhances the endogenous expression levels of key PXR-regulated genes like CYP3A4, CYP2C9, MDR1 and UGT1A1. In addition, mammalian two-hybrid assay exhibited enhanced interaction between PXR and co-activator SRC-1. EMSA results revealed that SUMOylation has no influence on the DNA binding ability of PXR. In silico analysis suggested that PXR protein contains four putative SUMOylation sites, centered at K108, K129, K160 and K170. In addition to this, we identified the presence of NDSM (Negative charge amino acid Dependent SUMOylation Motif) in PXR. Substitution of all its four putative lysine residues along with NDSM abolished the effect of SUMO-1-mediated transactivation function of PXR. Furthermore, we show that interaction between PXR and E2-conjugation enzyme UBCh9, an important step for implementation of SUMOylation event, was reduced in case of NDSM mutant PXRD115A. Overall, our results suggest that SUMOylation at specific sites on PXR protein are involved in enhancement of transcription function of this receptor.
authors.affiliation: Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi 110067, India.
authors.lastname: Priyanka
authors.affiliation: Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi 110067, India.
authors.forename: Deepak
authors.initials: D
authors.lastname: Kotiya
authors.affiliation: Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi 110067, India.
authors.forename: Manjul
authors.initials: M
authors.lastname: Rana
authors.affiliation: School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
authors.forename: N
authors.initials: N
authors.lastname: Subbarao
authors.affiliation: School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
authors.forename: Niti
authors.initials: N
authors.lastname: Puri
authors.affiliation: Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi 110067, India. Electronic address: rktyagi@yahoo.com.
authors.forename: Rakesh K
authors.initials: RK
authors.lastname: Tyagi
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D008954:Models, Biological; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D000077297:Pregnane X Receptor; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D055550:Protein Stability; D011987:Receptors, Steroid / Q000737:chemistry* / Q000235:genetics*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism*; D013329:Structure-Activity Relationship; D058207:Sumoylation; D014158:Transcription, Genetic; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism
chemical_list: D050505:Mutant Proteins; D000077297:Pregnane X Receptor; D011987:Receptors, Steroid; D025841:Small Ubiquitin-Related Modifier Proteins; D004247:DNA; C000601635:UBE2E3 protein, human; D044763:Ubiquitin-Conjugating Enzymes
keywords: Nuclear receptor; PXR; SUMOylation; Transcription factor; Xenobiotic metabolism