Wilms' tumor gene product WT1 arrests macrophage differentiation of HL-60 cells through its zinc-finger domain

Wilms' tumor is associated with mutations of WT1, a zinc-finger transcription factor that is essential for the development of the metanephric kidney and the urogenital system. High levels of WT1 expression also have been detected in myeloid leukemia cells, suggesting that WT1 may be important in other neoplasms as well. To seek a role of high level expression of WT1 in the differential arrest characteristic of myeloid leukemia, WT1 or its zinc-finger domain alone was stably expressed in human promyeloid leukemia (HL-60) cells and the ability of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) to induce macrophage differentiation was examined. HL-60 cell differentiation was completely arrested in TPA treated cells that expressed WT1 or its zinc-finger domain alone whereas TPA fully induced macrophage differentiation in control HL-60 cells, indicating that high level expression of WT1 is capable of differentiation arrest of myeloid cells and that its effect may be mediated through its zinc-finger domain. To determine if the zinc-finger domain of WT1 directly influences transcription, it was brought to promoter DNA as a fusion protein with the Ga14 DNA binding domain. The fusion protein failed to regulate transcription of a reporter gene but. when the zinc-finger domain of WT1 was brought to DNA with a promoter containing two upstream WT1-binding sites, reporter gene expression was activated approximately threefold, suggesting that WT1 interferes with myeloid differentiation through the ability of its zinc-finger domain to compete with other transcription factors for common promoter elements. (C) 1999 Academic Press.