Tumour necrosis factor-alpha depletes histone deacetylase 1 protein through IKK2

Class I histone deacetylases (HDACs) are ubiquitous enzymes that repress gene expression by deacetylating histone tails and promoting chromatin compaction. Pro-inflammatory agents activate programmes of gene expression through transcription factors such as nuclear factor-kappaB (NF-kappaB), even in the context of ubiquitous HDAC activity. How this is accomplished remains unknown. We found that cells treated with the pro-inflammatory cytokine tumour necrosis factor-alpha rapidly and substantially reduced HDAC1 protein levels without affecting other class I HDACs. In addition, HDAC1 depletion occurred through protein degradation, required IKK2 activity and resulted in increased transcription from both NF-kappaB-associated and unassociated gene promoters. Our study suggests that the activation of programmes of gene expression by pro-inflammatory agents requires global changes in specific critical epigenetic regulators such as HDAC1.