A far upstream element stimulates c-myc expression in undifferentiated leukemia cells

Area of Science:

• Molecular Biology
• Gene Regulation
• Cancer Cell Biology

Background:

• The c-myc gene is crucial for cell proliferation and is often dysregulated in cancer.
• Understanding the regulation of c-myc expression is vital for developing targeted cancer therapies.

Purpose of the Study:

• To investigate the regulatory elements controlling c-myc expression, particularly in response to differentiation-inducing agents.
• To identify specific DNA-binding factors that interact with upstream elements of the c-myc gene.

Main Methods:

• Exonuclease assays to detect DNA-protein interactions in vitro.
• Electrophoretic mobility shift assays (EMSA) to analyze binding activity.
• Reporter gene assays using a chimeric c-myc-CAT construct to assess regulatory function.

Main Results:

• Identified a far upstream element (FUSE), over 1500 base pairs upstream of the c-myc promoter P1, that binds a sequence-specific factor.
• This binding activity was lost upon dimethyl sulfoxide (Me2SO) treatment, correlating with the shut-off of c-myc expression in leukemia cell lines (HL-60, U-937).
• The FUSE element's binding activity was cell-line specific and appeared to potentiate c-myc expression, suggesting a positive regulatory role.

Conclusions:

• The far upstream element (FUSE) and its associated binding protein are involved in the positive regulation of c-myc expression.
• FUSE-mediated regulation is specific to cell type and differentiation status, contributing to the precise control of c-myc levels.