Heterozygous PU.1 mutations were reported in some patients with acute myeloid leukemia (AML), but not in AML with translocation t(8;21), which gives rise to the fusion gene AML1-ETO.     ///    The myeloid master regulator transcription factor PU.1 is inactivated by AML1-ETO in t(8;21) myeloid leukemia..     ///    "Thus, the function of PU.1 is down-regulated by AML1-ETO in t(8;21) myeloid leukemia, whereas overexpression of PU.1 restores normal differentiation.. "    ///    "AML1-ETO down-regulates the transactivation capacity of PU.1 in myeloid U937 cells, and the expression levels of PU.1 target genes in AML French-American-British (FAB) subtype M2 patients with t(8;21) were lower than in patients without t(8;21). "    ///    AML1-ETO physically binds to PU.1 in t(8;21)(+) Kasumi-1 cells.     ///    "AML1-ETO binds to the beta(3)beta(4) region in the DNA-binding domain of PU.1 and displaces the coactivator c-Jun from PU.1, thus down-regulating the transcriptional activity of PU.1. "    ///    Here we report a negative functional impact of AML1-ETO on the transcriptional activity of PU.1.     ///    Conditional expression of AML1-ETO causes proliferation in mouse bone marrow cells and inhibits antiproliferative function of PU.1.     ///    This physical interaction of AML1-ETO and PU.1 did not abolish the DNA-binding capacity of PU.1. 