1. C/EBP alpha:AP-1 leucine zipper heterodimers bind novel DNA elements, activate the PU.1 promoter and direct monocyte lineage commitment more potently than C/EBP alpha homodimers or AP-1.
- Author
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Cai DH, Wang D, Keefer J, Yeamans C, Hensley K, and Friedman AD
- Subjects
- Amino Acid Sequence, Animals, CCAAT-Enhancer-Binding Protein-alpha genetics, Cells, Cultured, DNA metabolism, Dimerization, Gene Expression Regulation physiology, Humans, Mice, Mice, Inbred C57BL, Molecular Sequence Data, Monocytes metabolism, Promoter Regions, Genetic physiology, Protein Binding genetics, Proto-Oncogene Proteins biosynthesis, Rats, Trans-Activators biosynthesis, CCAAT-Enhancer-Binding Protein-alpha metabolism, Cell Differentiation physiology, Cell Lineage physiology, Leucine Zippers physiology, Monocytes cytology, Proto-Oncogene Proteins genetics, Trans-Activators genetics, Transcription Factor AP-1 metabolism
- Abstract
The basic-region leucine zipper (BR-LZ or bZIP) transcription factors dimerize via their LZ domains to position the adjacent BRs for DNA binding. Members of the C/EBP, AP-1 and CREB/ATF bZIP subfamilies form homodimeric or heterodimeric complexes with other members of the same subset and bind-specific DNA motifs. Here we demonstrate that C/EBPalpha also zippers with AP-1 proteins and that this interaction allows contact with novel DNA elements and induction of monocyte lineage commitment in myeloid progenitors. A leucine zipper swap:gel shift assay demonstrates that C/EBPalpha zippers with c-Jun, JunB or c-Fos, but not with c-Maf or MafB. To evaluate activities of specific homodimers or heterodimers we utilized LZs with acid (LZE) or basic (LZK) residues in their salt bridge positions. C/EBPalphaLZE:C/EBPalphaLZK preferentially binds a C/EBP site, c-JunLZE:c-FosLZK an AP-1 site and C/EBPalphaLZE:c-JunLZK a hybrid element identified as TTGCGTCAT by oligonucleotide selection. In murine myeloid progenitors, C/EBPalpha:c-Jun or C/EBPalpha:c-Fos LZE:LZK heterodimers induce monocyte lineage commitment with markedly increased potency compared with C/EBPalpha or c-Jun homodimers or c-Jun:c-Fos heterodimers, demonstrating a positive functional consequence of C/EBP:AP-1 bZIP subfamily interaction. C/EBPalpha:cJun binds and activates the endogenous PU.1 promoter, providing one mechanism for induction of monopoiesis by this complex.
- Published
- 2008
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