Genomic sequencing of the 5'-flanking region of the mouse beta-globin major gene in expressing and nonexpressing mouse cells.

Genomic sequencing of two CG sites located in the 5'-flanking promoter region of the mouse beta-globin major gene shows these sites to be heavily methylated in the DNA from L929 mouse fibroblasts, a cell line that does not express the beta-globin gene. By contrast, the same CG sites in the DNA obtained from murine erythroleukemia cells, which can express the beta-globin gene, are unmethylated. The results suggest that either differentiation of progenitor cells to form the erythroid precursor murine erythroleukemia cell and/or transformation by the Friend virus group leads to demethylation of these CG sites. Final activation of the transcription process for the mouse beta-globin gene does not require demethylation in the 5'-promoter region of the DNA.