503 cells transduced with PU.1 express markers of neutrophil terminal differentiation. RNA was prepared from PLAP⁺ PU.1-transduced 503 (503-PU) cells and analyzed by RT-PCR. mRNA for secondary granule genes neutrophil collagenase (mNC) and neutrophil gelatinase (mNG) is present in 503-PU as well as normal neutrophils, but not in 503 or 503 transduced with G-CSF receptor (503-GR). The far righthand lane of each gel contains a 100-bp DNA ladder.