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cDNA cloning and functional analysis of a truncated STAT5a protein from autonomously growing FDCP-1 cells
1Medical Faculty, Institute of Medical Biochemistry, University of Rostock, Schillingallee 70, PF100888, 18055, Rostock, Germany. thomas.bittorf@med.uni-rostock.de
Abstract:
The transcription factor STAT5 is activated by multiple hematopoietic cytokine receptors and has been implicated in the induction of cellular processes such as differentiation, proliferation and antiapoptotic activities. Here, we report cloning of the cDNA and characterization of a mutant STAT5a protein that is expressed in interleukin-3 (IL-3)-independently growing FDCP-1 cells. Analysis of the cDNA revealed a deletion of both the transactivation and the SH2 domains. Stable expression of the protein in parental IL-3-dependent cells results in elevated DNA binding activity of wild type (WT)-STAT5 in the nucleus, enhanced growth rates and a reduced susceptibility to undergo apoptosis after withdrawal of IL-3. Although the protein is not present in DNA/protein complexes in the nucleus, we observed pronounced effects on IL-3-induced signal transduction. The results suggest competition of the mutant protein with cytosolic mechanisms regulating STAT5 activity. In conclusion, the data support the hypothesis of an involvement of STAT5 in mitogenic and antiapoptotic signaling.
Insights
A mutated STAT5a protein lacking key domains drives IL-3 independent cell growth and survival. This mutant STAT5a impacts wild-type STAT5 activity, suggesting a role in cell proliferation and anti-apoptosis signaling.
Area of Science:
- Molecular Biology
- Cell Biology
- Signal Transduction
Background:
- Signal transducer and activator of transcription 5 (STAT5) is crucial for cytokine-mediated cellular processes.
- STAT5 activation is linked to differentiation, proliferation, and anti-apoptotic activities in hematopoietic cells.
Purpose of the Study:
- To clone and characterize a mutant STAT5a protein found in IL-3-independent FDCP-1 cells.
- To investigate the functional impact of this mutant STAT5a on wild-type STAT5 activity and cellular responses.
Main Methods:
- cDNA cloning and sequencing of the mutant STAT5a protein.
- Stable expression of the mutant protein in IL-3-dependent cells.
- Analysis of STAT5 DNA binding activity, cell growth rates, and apoptosis susceptibility.
Main Results:
- The mutant STAT5a cDNA revealed deletions in the transactivation and SH2 domains.
- Expression of mutant STAT5a in parental cells increased WT-STAT5 nuclear DNA binding activity.
- Cells expressing mutant STAT5a exhibited enhanced growth and reduced apoptosis upon IL-3 withdrawal.
Conclusions:
- The mutant STAT5a protein, despite not binding DNA, influences STAT5 signaling pathways.
- Results suggest the mutant protein interferes with cytosolic mechanisms regulating STAT5.
- STAT5 plays a significant role in both mitogenic and anti-apoptotic signaling pathways.