Screening for MK-inducing factors. The 3T3 cells transfected with candidate transcription factors were cultured in MKLI medium. (A) Representative data of CD41 expression on 3T3 cells and 3T3 cells transfected with candidate transcription factors. (B) Mean ± SEM of percentage of cells that were CD41-positive after transfection with the empty vector or with various expression vectors (N = 3 and *P < .02 vs p45NF-E2, Maf G, and Maf K expression). (C) Representative flow data of CD42 expression on 3T3 cells transfected with either empty vector or p45NF-E2, Maf G, and Maf K vector (left). Bar graph of mean ± SEM for CD42b expression (N = 3 and *P < .02; right). (D) DNA ploidy analysis on 3T3 cells untransfected versus transfected with p45NF-E2, Maf G, and Maf K expression vector (N = 3; mean ± SEM %: 2N, 60.7 ± 2.2; 4N, 21.4 ± 3.2; 8N, 8.0 ± 0.9; and ≥ 16N, 9.6 ± 1.9).