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Transcriptional regulation of interleukin-3 expression in megakaryocytes
1Laboratory of Molecular Aspects of Hematopoiesis, Sloan-Kettering Institute, New York, NY, USA.
Abstract:
Interleukin-3 (IL-3) is a potent stimulator of megakaryocyte proliferation, and autocrine production of IL-3 by megakaryocytic leukemia cell lines and bone marrow-derived megakaryocytes has recently been demonstrated. To characterize the transcriptional regulation of IL-3 in megakaryocytes, we transiently transfected IL-3 promoter CAT constructs that contain variable amounts of 5' flanking sequences into the human CMK and CMK-6 megakaryocytic cell lines and identified two positive acting transcriptional regulatory regions, one located between bp -315 and -284, which contains consensus AP-1 and ets binding sites, and a second located between bp -173 and -61. DNase I footprinting assays using CMK or CMK-6 nuclear extracts demonstrate DNA-protein interactions in the identical region protected by T cell or natural killer cell nuclear extracts (between bp -165 to -128), and electrophoretic mobility shift assays demonstrate the binding of proteins to three distinct portions of this region. To characterize the transcription factors in megakaryocytic cells that could bind to these two regulatory regions, we performed Northern blot analyses, which showed the presence of ets-1, elf-1 (which is thought to be restricted to T cells), NF-IL3A and AML1 mRNAs, as well as c-fos, jun B, and jun D, but not c-jun mRNA. These studies show that the transcriptional regulation of IL-3 expression in megakaryocytic leukemia cell lines is similar, but not identical to normal human T cells.
Insights
Interleukin-3 (IL-3) transcriptional regulation in megakaryocytes involves specific DNA regions and transcription factors like ets-1 and NF-IL3A. This reveals similarities and differences compared to T cells.
Area of Science:
- Molecular Biology
- Hematology
- Gene Regulation
Background:
- Interleukin-3 (IL-3) is crucial for megakaryocyte proliferation.
- Autocrine IL-3 production is observed in megakaryocytic leukemia cell lines and bone marrow-derived megakaryocytes.
Purpose of the Study:
- To elucidate the transcriptional regulation of IL-3 in megakaryocytes.
- To identify key regulatory regions and transcription factors involved in IL-3 gene expression within megakaryocytic cells.
Main Methods:
- Transient transfection of IL-3 promoter CAT constructs into human CMK and CMK-6 megakaryocytic cell lines.
- DNase I footprinting and electrophoretic mobility shift assays to identify DNA-protein interactions.
- Northern blot analysis to detect specific mRNA transcripts.
Main Results:
- Two positive transcriptional regulatory regions in the IL-3 promoter were identified (-315 to -284 and -173 to -61).
- Specific DNA-protein interactions were confirmed in the -165 to -128 region.
- Expression of ets-1, elf-1, NF-IL3A, AML1, c-fos, jun B, and jun D mRNAs was detected in megakaryocytic cells.
Conclusions:
- Transcriptional regulation of IL-3 in megakaryocytic leukemia cell lines shares similarities with normal human T cells.
- Distinct transcription factors bind to identified regulatory regions, influencing IL-3 gene expression in megakaryocytes.