MZF1 and myeloid leukemia: c-myb mRNA elongation can be blocked in intron I in a cell-type-dependent manner.10, 11, 12 c-Myb can negatively regulate its own expression.13 WT1 (Wilms Tumor 1), MZF1 (myeloid zinc finger 1), and PU.1 can downregulate the c-myb promoter activity, while the Ets and c-Jun/JunD transcription factors activate the promoter.14, 15, 16, 17, 18, 19 But these data from previous studies cannot completely elucidate the mechanisms of c-myb expression regulation during the differentiation of murine myeloid leukemia M1 cell.