HDAC inhibition by TSA intensifies ATRA-induced histone H4 hyperacetylation on chromatin of RARβ promoter in ATRA-resistant NB4-MRA1 APL cells.

Cross-linked chromatin preparations of ATRA-sensitive NB4 and ATRA-resistant NB4-MRA1, NB4-MR4, and UF-1 APL cells untreated or treated with 1 μM ATRA or 200 nM TSA, and the combination of ATRA with TSA were immunoprecipitated with an antibody against acetylated tails of histone H4. Immunoprecipitated and input material was analyzed by PCR using primers corresponding to the RARE region of theRARβ promoter.