Acetylation of RORβ by histone acetyltransferase p300 and deacetylation by SIRT1 modulates receptor stability, turnover and transcriptional activity

RORβ is an understudied nuclear receptor recently implicated in numerous pathologies. Using immunoprecipitation mass spectrometry, the transcription factor coregulatory protein and histone acetyltransferase p300 (EP300) was identified as a direct interacting protein of RORβ. Crosslinking mass spectrometry (XL-MS) confirmed that p300 interacts with the DNA binding domain (DBD), hinge region, and ligand binding domain (LBD) of RORβ. Both p300 and SIRT1 impact the turnover rate and transcriptional activity of RORβ. p300-dependent acetylation sites were found to be constrained to the DBD and hinge region of RORβ and were deacetylated by SIRT1. Sites that were ubiquitinated in the presence of p300 and SIRT1 were also discovered, with some sites sensitive to proteasome inhibitor. A constitutively acetylated mimic at K176 in the hinge prevented ubiquitination of RORβ at distal sites. Uncovering regulatory mechanisms of RORβ via protein interactions and PTMs will provide strategies for development of therapeutics targeting the receptor.