Analysis of a novel HDAC8-H1.3 complex in several human carcinoma cell lines
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The compaction level of chromatin regulates DNA accessibility, gene expression, and cell division. Transcription factors and other proteins cannot access the DNA within compacted chromatin. Two types of proteins that contribute to chromatin compaction are histone deacetylases (HDACs) and linker histones (H1s). H1s are chromatin-binding structural proteins required for the formation of the higher order chromatin structure. H1 subtypes also differentially regulate transcription and apoptosis. HDACs cause chromatin compaction by deacetylating lysine residues on core histone tails, causing core histones to closely interact with DNA. HDACs regulate many other cellular processes including: mitosis, intracellular trafficking, microtubule dynamics, and cell cycle events, through deacetylation of non-histone proteins. This work describes a novel HDAC8-H1.3 protein complex found in several human cancerous cell lines. The goal of this research was to gather insight as to the function of the HDAC8-H1.3 complex using co-immunoprecipitation, chromatin-binding electrophoretic mobility shift assays, deacetylation assays, immunocytochemistry, confocal microscopy, and complex protein mixture identification by LC/MS/MS. The hypothesis was that HDAC8 and H1.3 work synergistically to cause chromatin compaction. Results showed that H1.3, but not HDAC8 binds to nucleosomes. HDAC8 was found to deacetylate H1.3. In MCF-7 cells the complex was found to associate with ER-Golgi associated vesicles and late endosomes during interphase. This is the first report for a non-mitotic cytoplasmic association of a linker histone and HDAC. Also, this is the first reported association of a linker histone with vesicle trafficking.