HDAC7 influences ER-⍺ transcription via NCoR-HDAC3 dissociation

HDAC7 (histone deacetylase 7) is involved in many diseases, including breast cancer. HDAC7 regulates gene expression epigenetically by assisting in the deacetylation of nucleosomal histones to remodel chromatin. However, HDAC7 is a pseudodeacetylase that displays weak enzymatic activity and cannot directly deacetylate histones. Instead, HDAC7 scaffolds histones to active HDAC3 (histone deacetylase 3) via NCoR (nuclear receptor corepressor) to regulate transcription. Recent evidence documented that the inactive pseudo-active site of HDAC7 binds an acetyllysine on the AR (androgen receptor) transcription factor to disrupt HDAC3-NCoR scaffolding and activate transcription. To expand on the acetylation-dependent reversible scaffolding observed with AR, here HDAC7 binding was tested with additional nuclear receptors, including GR (glucocorticoid receptor), PR (progesterone receptor), TR (thyroid receptor), and RXR (retinoid x receptor), with particular focus on ER-⍺ (estrogen receptor alpha). Acetyllysine-dependent HDAC7-NCoR-HDAC3 binding and gene expression was established with ER-⍺ in a physiologically relevant breast cancer cell line, which substantiates acetyllysine-mediated reversible scaffolding by HDAC7 in the epigenetic regulation of nuclear receptor transcriptional activation.