Expression of PU.1 and Syk requires the combination of 5-aza-dC treatment and Oct2 or PU.1 expression. (A) L428 cells stably overexpressing Oct2 or Oct2 plus BOB.1/OBF.1 transcription factors as well as L428 cells stably transfected with the corresponding empty vectors were treated with 5-aza-dC as described in the legend to Figure 1. The gene expression was assessed by RT-PCR using 35 amplification cycles. (B) 5 × 106 L428 cells were either left untreated or treated with 1 μM 5-aza-dC. After 48 hours the cells were transiently transfected with mouse PU.1 expression vector or the empty vector as control. Another 48 hours later, cells were harvested and used for RT-PCR analysis. PU.1m corresponds to the ectopic murine PU.1, and PU.1h represents the endogenous human PU.1 gene. The experiments were done at least in triplicate.