Bone marrow (BM) cells were infected with Neo or dominant negative nuclear factor YA (NF-YA DN) retroviral particles, seeded in 1 mL methylcellulose supplemented with G418 (650 μg/mL), and treated with either interleukin 3 (IL-3; 10%) alone or macrophage colony-stimulating factor (MCSF) plus IL-6 (100 ng/mL). After 8 days G418-resistant colonies were counted. Data are the average of 3 independent experiments, with SE indicated. According to the Studentt test, the observed difference in the means of Neo–infected BM and NF-YA DN–infected BM treated with MCSF plus IL-6 is significant with more than 95% confidence.