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Human gamma-globin gene promoter element regulates human beta-globin gene developmental specificity
1Department of Biochemistry and Molecular Genetics, School of Medicine and Dentistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
Nucleic Acids Research
|July 25, 2000
Summary
The CACCC box in the gamma-globin gene is crucial for switching off beta-globin expression during fetal development. This finding clarifies the molecular mechanisms behind human beta-globin gene developmental specificity.
Area of Science:
- Molecular Biology
- Genetics
- Developmental Biology
Background:
- Beta-thalassemias show persistent fetal hemoglobin, suggesting competition for the beta-globin locus control region (LCR).
- Gamma- to beta-globin gene switching is vital for normal erythropoiesis and is influenced by regulatory elements.
Purpose of the Study:
- To identify regulatory sequences essential for gamma-globin gene advantage during early development.
- To elucidate the role of specific transcription factor binding sites in globin gene switching.
Main Methods:
- Generation of stable transgenic mouse lines with modified LCR gamma-beta constructs.
- Deletion analysis of gamma-globin 5'-flanking DNA sequences.
- Primer extension analysis of RNA from various embryonic tissues.
- Site-directed mutagenesis of transcription factor binding sites within the gamma-globin promoter.
Main Results:
- A region between -202 and -130 bp of the gamma-globin promoter suppressed beta-globin expression early in development.
- Mutation of the gamma-globin CACCC box, but not other sites (GATA(p), Oct1, GATA(d)), led to high beta-globin expression in early embryos.
- The gamma-globin CACCC box is critical for developmental specificity of human beta-globin gene expression.
Conclusions:
- The CACCC box in the gamma-globin gene promoter plays a key role in regulating developmental globin gene switching.
- Gamma-CACCC box binding factors likely mediate interactions with the LCR to enhance gamma-globin and suppress beta-globin expression in fetal erythroid cells.