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.
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.
Cai
D H
DH
Division of Pediatric Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA.
Wang
D
D
Keefer
J
J
Yeamans
C
C
Hensley
K
K
Friedman
A D
AD
D000595:Amino Acid Sequence; D000818:Animals; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D019070:Cell Lineage / Q000502:physiology*; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D019281:Dimerization; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D016350:Leucine Zippers / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009000:Monocytes / Q000166:cytology* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology; D011485:Protein Binding / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics*; D051381:Rats; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics*; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D000099232:Proto-Oncogene Protein Spi-1
D022763:CCAAT-Enhancer-Binding Protein-alpha; D004247:DNA; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D018808:Transcription Factor AP-1; D000099232:Proto-Oncogene Protein Spi-1