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Changes in in vivo protein-DNA interactions occur at the c-myc P2 promoter during differentiation
M Bryans1, J C Lang, N M Wilkie
1Department of Hematology/Oncology, Ohio State University Comprehensive Cancer Center, 1248 James Cancer Hospital and Research Institute, Columbus 43210.
Abstract:
Down regulation of the c-myc gene is a prerequisite for the differentiation of a number of cell types. Studies have shown that two mechanisms of inactivation are involved in c-myc repression: a block of the elongation of RNA polymerase followed by transcriptional inactivation mediated through promoter sequences. In this study DMS in vivo footprinting was performed on the P2 promoter region of c-myc in differentiated and undifferentiated HL60 cells. A differentiation-specific footprint was observed at G residues immediately upstream of the TATA box. This observation occurred only in cells differentiated for 48 hours or more and hence is likely to be involved in the repression of c-myc by promoter inactivation.
Insights
Down regulation of the c-myc gene is crucial for cell differentiation. This study identified a specific DNA footprint in the c-myc promoter region of differentiated cells, suggesting a novel mechanism for gene repression.
Area of Science:
- Molecular Biology
- Gene Regulation
- Cell Differentiation
Background:
- c-myc gene down-regulation is essential for cell differentiation.
- Two known mechanisms of c-myc repression involve RNA polymerase elongation block and promoter inactivation.
Purpose of the Study:
- To investigate the role of promoter inactivation in c-myc gene repression during cell differentiation.
- To identify specific DNA-protein interactions at the c-myc P2 promoter in HL60 cells.
Main Methods:
- Performed dimethyl sulfate (DMS) in vivo footprinting on the c-myc P2 promoter region.
- Analyzed HL60 cells at various differentiation stages.
Main Results:
- A differentiation-specific footprint was detected at guanine (G) residues upstream of the TATA box.
- This footprint was observed in cells differentiated for 48 hours or longer.
- The observed footprint suggests a role for promoter inactivation in c-myc repression.
Conclusions:
- The study provides evidence for a differentiation-specific mechanism of c-myc gene repression.
- Promoter inactivation, mediated by specific DNA-protein interactions, is likely involved in repressing c-myc during cell differentiation.