HDAC inhibitor TSA potentiates ATRA induction ofRARβ mRNA expression in the ATRA-resistant NB4-MRA1 APL cells harboring the mutant I410T PML/RARα.

Ribonuclease protection analysis for RARβ expression of 50 μg total RNA isolated from 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 for 28 hours. The RNase-protected band corresponding to RARβ is identified, andGAPDH expression was used as a quantitative loading control. Yeast tRNA (y-tRNA) was included as a negative control to verify the specificity of the probes.