Overexpression of the zinc finger protein MZF1 inhibits hematopoietic development from embryonic stem cells: Correlation with negative regulation of CD34 and c-myb promoter activity

Zinc finger genes encode proteins that act as transcription factors. The myeloid zinc finger 1 (MZF1) gene encodes a zinc finger protein with two DNA- binding domains that recognize two distinct consensus sequences, is preferentially expressed in hematopoietic cells, and may be involved in the transcriptional regulation of hematopoiesis-specific genes. Reverse transcription-PCR analysis of human peripheral blood CD34⁺ cells cultured under lineage-restricted conditions demonstrated MZFI expression during both myeloid and erythroid differentiation. Sequence analysis of the 5'-flanking region of the CD34 and c-myb genes, which are a marker of and a transcriptional factor required for hematopoietic proliferation and differentiation, respectively, revealed closely spaced MZFI consensus binding sites found by electrophoretic mobility shift assays to interact with recombinant MZFI protein. Transient or constitutive MZFI expression in different cell types resulted in specific inhibition of chloramphenicol acetyltransferase activity driven by the CD34 or c-myb 5'-flanking region. To determine whether transcriptional modulation by MZFI activity plays a role in hematopoietic differentiation, constructs containing the MZFI cDNA under the control of different promoters were transfected into murine embryonic stem cells which, under defined in vitro culture conditions, generate colonies of multiple hematopoietic lineages. Constitutive MZFI expression interfered with the ability of embryonic stem cells to undergo hematopoietic commitment and erythromyeloid colony formation and prevented the induced expression of CD34 and c-myb mRNAs during differentiation of these cells. These data indicate that MZFI plays a critical role in hematopoiesis by modulating the expression of genes involved in this process.