FIG. 1.

Expression of the histone H4/n gene during PMA-induced differentiation of HL-60 cells. (A) Northern blot analysis was performed with total RNA prepared from PMA-treated (differentiated) and untreated (proliferating) HL-60 cells at the indicated times of treatment from two separate experiments. RNAs were hybridized with probes spanning the coding regions of the genes for H4/n and p21. The H4/n probe detects histone H4 mRNAs derived from multiple members of the histone H4 gene family. The ethidium bromide (EthBr)-stained gel is shown as a control for RNA integrity and quantitation. (B) Semiquantitative RT-PCR was performed with the same RNA samples and primers that detect transcripts specific for the H4/n gene. GAPDH was used as an internal control. The right lane (M) shows a 100-bp repeat marker.