The state of DNA methylation in the promoter regions of the human red cell membrane protein (band 3, protein 4.2, andβ-spectrin) genes

The state of methylation of the 5′-CpG-3′ sites is known to be linked to the regulation of promoter function by modulating DNA-protein interactions and to the structure of chromatin. As part of a project to determine methylation patterns in the human genome, the methylation profiles were examined in genes for the human erythroid membrane proteins; protein 4.2 (P4.2), gene (ELB42), band 3 (B3), gene (EPB3), and β-spectrin (β-Sp), gene (SPTB). The bisulfite protocol of the genomic sequencing method was applied.(1) In the DNA from peripheral white blood cells, the promoter regions of EPB3 and ELB42 were extensively methylated, but the promoter of SPTB was totally unmethylated. (2) During erythroid differentiation, (i) ELB42 was unmethylated in DNAs from the cell line UT-7/EPO, but became methylated (55−93 %) in cultured erythroblasts from peripheral BFU-E. The mRNA from ELB42 was first detected in early erythroblasts and protein 4.2 was expressed in late erythroblasts. (ii) EPB3 was consistently methylated in UT-7/EPO and also in cultured erythroblasts from burst forming unit erythroid (BFU-E) from peripheral blood. EPB3 and ELB42 were efficiently transcribed in UT-7 cells only after erythropoietin stimulation. (iii) SPTB remained unmethylated in DNAs from UT-7/EPO and cultured erythroblasts. (3) We also investigated methylation profiles in peripheral white blood cells from patients with erythroid diseases, like complete P4.2 deficiency due to ELB42 mutations, hereditary spherocytosis with EPB3 mutations, and hereditary elliptocytosis with SPTB mutations. The methylation profiles of the promoter regions of these three genes were essentially identical to those in healthy individuals.