PIASγ Represses the Transcriptional Activation Induced by the Nuclear Receptor Nurr1

Abstract

Nurr1 is a transcription factor essential for the development of ventral dopaminergic neurons. In search for regulatory mechanisms of Nurr1 function, we identified the SUMO (small ubiquitin-like modifier)-E3 ubiquitinprotein isopeptide ligase, PIAS␥, as an interaction partner of Nurr1. Overexpressed PIAS␥ and Nurr1 co-localize in the nuclei of transfected cells, and their interaction is demonstrated through co-immunoprecipitation and glutathione S-transferase pulldown assays. Co-expression of PIAS␥ with Nurr1 results in a potent repression of Nurr1-dependent transcriptional activation of an artificial NGFI-B response element (NBRE) reporter as well as of a reporter driven by the native tyrosine hydroxylase promoter. We identified two consensus sumoylation sites in Nurr1. The substitution of lysine 91 by arginine in one SUMO site enhanced the transcriptional activity of Nurr1, whereas the substitution of lysine 577 by arginine in the second SUMO site decreased transcriptional activity of Nurr1. Interestingly, PIAS␥-induced repression of Nurr1 activity does not require the two sumoylation sites, because each mutant is repressed as efficiently as the wild type Nurr1. In addition, the mutations do not alter Nurr1 nuclear localization. Finally, we provide evidence that Nurr1 and PIAS␥ co-exist in several nuclei of the rodent central nervous system by demonstrating the co-expression of Nurr1 protein and PIAS␥ mRNA in the same cells. In conclusion, our studies identified PIAS␥ as a transcriptional co-regulator of Nurr1 and suggest that this interaction may have a physiological role in regulating the expression of Nurr1 target genes.

Essential role for DNA-PK-mediated phosphorylation of NR4A nuclear orphan receptors in DNA double-strand break repair

“…4). NR4A proteins have previously been shown to interact with other proteins implicated in DNA repair (Galleguillos et al 2004;Ohkura et al 2008;Rambaud et al 2009). Thus, the corresponding mRNAs (and the mRNA encoding the Ku80 subunit of DNA-PK) were down-regulated by siRNA transfection in U2OS cells, followed by exposure to IR and analysis of NR4A cellular distribution.…”

Nuclear Import and Export Signals Control the Subcellular Localization of Nurr1 Protein in Response to Oxidative Stress*

“…Nurr1 is regulated primarily by phosphorylation by ERK or AKT, sumoylation by protein inhibitor of activated STAT-␥, or dimerization with glucocorticoid or retinoid receptors (6,16,(27)(28)(29)(30)(31). However, little is known about a possible mechanism involved in regulation of its subcellular localization under both basal and stimulus-induced conditions.…”

Structural Basis for the Cell-specific Activities of the NGFI-B and the Nurr1 Ligand-binding Domain

“…Importantly, the AF2 does not directly interact with SRCs, p300, pCAF, or DRIP205, and little is known about the regulation of its activity (12,25,27,28). However, the co-repressor SMRT, the atypical orphan receptor DAX-1, and the SUMO ubiquitin ligase PIAS␥ have been reported to interact with the LBD of either NGFI-B or Nurr1, and play a role in AF2 regulation (22,29,30).…”