Neutrophils deficient in PU.1 fail to transcribe the gp91^phoxgene. RNA was prepared, reverse transcribed, and subjected to PCR as described in Materials and Methods. These samples were obtained from 2-week cultures. All NADPH oxidase component subunits were detectable in one normal (lane 4) and three different PU.1-deficient cultured neutrophil samples (lanes 1 through 3) by this method except for gp91, which was only found in normal cells. Controls for amplification of DNA in the absence of reverse transcription for each reaction were negative; these data are not shown. bp, base pairs.