Silencing of Transcription of the Human Luteinizing Hormone Receptor Gene by Histone Deacetylase-mSin3A Complex

Ying Zhang,Maria L Dufau

doi:10.1074/jbc.m204417200

Abstract

Modification of chromatin structure by histone acetylases and deacetylases is an important mechanism in modulation of eukaryotic gene transcription. The present study investigated regulation of the human luteinizing hormone receptor (hLHR) gene by histone deacetylases. Inhibition of histone deacetylases (HDACs) by trichostatin A (TSA) increased hLHR promoter activity by 40-fold in JAR cells and markedly elevated endogenous hLHR mRNA levels. Acetylated histones H3 and H4 accumulated in TSA-treated cells and associated predominantly with the hLHR promoter. Furthermore, TSA significantly enhanced the recruitment of RNA polymerase II to the promoter. One of the two Sp1 sites essential for basal promoter activity was identified as critical for the TSA effect, but the binding of Sp1/Sp3 to this site remained unchanged in the absence or presence of TSA. A multiprotein complex was recruited to the hLHR promoter via interaction with Sp1 and Sp3, in which HDAC1 and HDAC2 were docked directly to Sp1-bound DNA and indirectly to Sp3-bound DNA through RbAp48, while mSin3A interacted with both HDACs. HDAC1 and HDAC2 were shown to potently repress the hLHR gene transcription, and mSin3A potentiated the inhibition mediated by HDAC1. Our studies have demonstrated that the HDAC-mSin3A complex has an important role in the regulation of hLHR gene transcription by interaction with Sp1/Sp3 and by region-specific changes in histone acetylation and polymerase II recruitment within the hLHR promoter.

Highlights

Characterization of the LHR gene promoter from different species has provided insights into regulatory mechanism of LHR gene transcription
Histone Deacetylase Inhibitors Activated the Transcription of Human LHR Gene—To investigate whether transcription of the human LHR gene (hLHR) gene was subject to modulation through chromatin modification related to histone acetylation and deacetylation, transient transfection studies using reporter gene analysis of the hLHR promoter activity was carried out in JAR cells treated with or without two histone deacetylases (HDACs) inhibitors, trichostatin A (TSA) and NaB
The present studies have demonstrated that inhibition of HDAC activities by TSA caused potent induction of both hLHR gene promoter activity and its endogenous mRNA expression level in JAR cells

Summary

Introduction

Characterization of the LHR gene promoter from different species has provided insights into regulatory mechanism of LHR gene transcription. Activation of the promoter activity at the same site by another orphan receptor, TR4, was only observed for the human LHR gene (hLHR). This difference was attributed to a single nucleotide base pair substitution at the core motif and absence of a guanine in the 3Ј adjacent sequence of the rat LHR promoter [8, 9]. Recent evidence have demonstrated that modification of nucleosomal histones by two opposing enzymes, histone acetyltransferases and histone deacetylases (HDACs), plays an active role in transcriptional regulation of a number of target genes (10 –13). An investigation of the modulation of hLHR gene transcription demonstrated that the histone deacetylase-mSin3A complex has a major role in silencing of Sp1/Sp3-driven hLHR gene transcription

Methods

Results

Conclusion