| Abstract: |
1,25-Dihydroxyvitamin D3 [1,25(OH)2D3], the hormonal ligand for vitamin D3, is a potent inducer of myeloid-leukemic-cell differentiation. Such cells differentiate exclusively into monocytes/macrophages in response to this ligand. Since 1,25(OH)2D3 transduces its hormone signal through the vitamin D3 receptor (VDR), a ligand-modulated transcription factor and member of the nuclear hormone receptor superfamily, we sought to identify direct VDR target genes induced during this differentiation process. To do so, we applied a modified differential screen with a nascent-RNA purification strategy using biases for immediate-early-response genes induced by 1,25(OH)2D3 in the myelomonocytic cell line U937. Using this screen, we had previously identified p21(Waf1/Cip1) as a gene transcriptionally induced by 1,25(OH)2D3 and demonstrated that this induction facilitates the differentiation of U937 cells into monocytes/macrophages (24). Here, we describe in detail our differential screen strategy and the identification and isolation of 20 1,25(OH)2D3-inducible genes or unknown cDNAs by means of this screen. One gene newly identified as a target of VDR regulation in myeloid cells is the homeobox HoxA10 gene. HoxA10 protein may act as a general regulator of cell growth, since overexpression of HoxA10 facilitated the differentiation of U937 cells into monocytes/macrophages independent of 1,25(OH)2D3 and acted to strongly inhibit the growth of the breast cancer cell line MCF-7 by arresting these cells in G1. |
| Keywords: |
signal transduction; human cell; dna-binding proteins; cell proliferation; gene overexpression; cell growth; cell differentiation; homeodomain proteins; calcitriol; tumor cells, cultured; breast neoplasms; gene expression regulation; gene expression regulation, neoplastic; transcription regulation; leukemia cell; leukemia, myeloid; ligands; gene induction; hormonal regulation; genetic techniques; ligand binding; g1 phase; growth inhibition; genes, homeobox; second messenger; colecalciferol; gene isolation; receptors, calcitriol; humans; human; female; priority journal; article; mink cell focus-forming virus
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