PC4 is a coactivator for basal and TSA‐induced Luteinizing Hormone Receptor (LHR) transcription

Abstract

The LHR has an essential role in sexual development and reproductive function, and its transcription is subject to several modes of regulation and multiple effectors. In this study we investigated PC4 coactivator function in the control of LHR transcription. In MCF‐7 and JAR cells, PC4 knockdown with siRNA significantly reduced the basal LHR promoter activity. While over‐expression of PC4 alone had no effect on the LHR promoter activity, it synergistically enhanced Sp1‐ but not Sp3‐mediated LHR transcriptional activity and GST‐pull down showed that PC4 interacted with Sp1. Moreover, DNA affinity precipitation assay revealed the association of PC4 with Sp1/Sp3 binding sites of the LHR gene promoter. This association was markedly increased by dephosphorylation of PC4 with treatment of calf intestinal phosphatase, suggesting a role of phosphorylation in the modulation of PC4/Sp1 interaction. Furthermore, PC4 was found to be involved in the activation of LHR gene expression by TSA in MCF‐7 cells, since the induced LHR transcription/expression was substantially reduced by >90% after knockdown of PC4 protein. Chromatin immunoprecipitation assay further showed significant occupancy of PC4 in the LHR promoter. Taken together, these studies have demonstrated another layer of LHR modulation whereby PC4 acts as a coactivator of Sp1 to contribute to the basal and TSA‐induced derepression of LHR transcription.