SHP represses transcriptional activity via recruitment of histone deacetylases

The orphan receptor short heterodimer partner (SHP) is a common partner for a great number of nuclear receptors, and it plays an important role in many diverse physiological events. In a previous study, we described SHP as a strong repressor of the androgen receptor (AR). Herein, we addressed the mechanism of action of its negative activity on transcription. We first investigated the intrinsic repressive potential of SHP and mapped two core repressive domains to the amino acids 170-210 and 210-240. From GST pull-down assays, we demonstrated a direct interaction between SHP and diverse histone deacetylases (HDACs) as well as a strong interaction between HDAC1 and SHP inhibitory domains. We further supported the evidence for an interaction between SHP and HDAC1 by showing their co-immunoprecipitation and provided evidence for the existence of a ternary complex comprising AR, SHP, and HDAC1. The use of trichostatin A (TSA), a specific inhibitor of HDAC activity, confirmed that HDACs significantly contribute to the intrinsic transrepressive activity of SHP. Finally, we showed that TSA reversed SHP-induced repression of AR, further emphasizing the relevance of the interaction between SHP and HDACs. This latter action affected in a very similar manner SHP-mediated repression of estrogen receptor alpha (ERalpha) transactivation. Altogether, our results indicate that SHP mediates most of its repressive effect through recruitment of HDACs and suggest that the physiological actions of SHP could be affected by HDAC inhibitors.