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Formation of STAT5-containing DNA binding complexes in response to colony-stimulating factor-1 and platelet-derived
1University of Melbourne, Department of Medicine, Royal Melbourne Hospital, Parkville 3050, Australia.
Abstract:
Colony-stimulating factor (CSF-1) activates several members belonging to the STAT (signal transducers and activators of transcription) family of transcription factors. We investigated the DNA binding complexes activated by CSF-1 in several cell lines and compared them with complexes activated by platelet-derived growth factor and interleukin 3. Our results indicate that the SIF-A complex activated by CSF-1 and platelet-derived growth factor may contain STAT3/STAT5 heterodimers binding to the high affinity SIF binding site, m67. In addition, both growth factors activate one or several STAT5-containing protein complexes binding to the prolactin-inducible element, PIE. The formation of these complexes was cell type and growth factor specific. Interleukin 3 activated only PIE binding complexes containing STAT5A and STAT5B and did not activate m67 binding complexes. It appears, therefore, that STAT5 cannot bind to m67 as a homodimer, but it can bind if it is dimerized with STAT3, whereas it can bind to the PIE element without being either complexed with STAT3 or any other known STAT protein, possibly as a homodimer or as STAT5A/STAT5B heterodimer. However, in addition, STAT5 may heterodimerize with other proteins and form novel PIE binding complexes.
Insights
Colony-stimulating factor (CSF-1) and platelet-derived growth factor activate STAT3/STAT5 heterodimers. STAT5 forms complexes with STAT3 or alone on specific DNA elements, showing cell-type and growth-factor specificity.
Area of Science:
- Cellular signaling pathways
- Molecular biology
- Transcription factor regulation
Background:
- Signal transducers and activators of transcription (STAT) proteins are key mediators of cellular responses to growth factors.
- Colony-stimulating factor (CSF-1) is known to activate STAT family members, but the specific DNA-binding complexes formed are not fully characterized.
Purpose of the Study:
- To investigate the DNA-binding complexes activated by CSF-1 in various cell lines.
- To compare CSF-1-activated complexes with those induced by platelet-derived growth factor (PDGF) and interleukin 3 (IL-3).
Main Methods:
- Analysis of DNA-binding complexes using electrophoretic mobility shift assays (EMSAs) in multiple cell lines.
- Comparison of STAT protein complex formation in response to different growth factors (CSF-1, PDGF, IL-3).
Main Results:
- CSF-1 and PDGF activate SIF-A complexes, potentially containing STAT3/STAT5 heterodimers, which bind to the m67 site.
- Both CSF-1 and PDGF induce STAT5-containing complexes binding to the prolactin-inducible element (PIE).
- IL-3 exclusively activates PIE-binding complexes containing STAT5A and STAT5B, without activating m67-binding complexes.
Conclusions:
- STAT5 binding to the m67 site requires heterodimerization with STAT3.
- STAT5 can bind to the PIE element as homodimers or STAT5A/STAT5B heterodimers, independent of STAT3.
- Novel PIE-binding complexes involving STAT5 heterodimerization with other proteins may exist.