Open AccessActive gene sequences are undermethylated.
Author(s) -
Tally Naveh-Many,
Howard Cedar
Publication year - 1981
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.78.7.4246
Subject(s) - cpg site , methylation , gene , dna methylation , cytosine , microbiology and biotechnology , biology , dna , deoxyribonuclease i , restriction enzyme , illumina methylation assay , differentially methylated regions , genome , genetics , biochemistry , gene expression , base sequence
The degree of methylation of active regions of the chromosome has been investigated by several techniques. DNase I (deoxyribonuclease I, EC 3.1.21.1) was used to introduce nicks in the active regions of the nucleus and thereby specifically label these areas. By using the methylation-specific restriction enzymes Hpa II and Hha I it could be shown that active genes are more sensitive to these probes than are other parts of the genome. In order to measure the amount of methylation at all CpG residues, DNA was nick-translated in the presence of [alpha-32P]dGTP as the sole nucleotide source and the methylated cytosine was detected by the standard nearest-neighbor analysis. Using this assay, we found that about 70% of all CpG sequences in animal cell DNA are methylated. In active nuclear regions that are sensitive to DNase I, only 30-40% of the CpG residues are methylated. This method was also employed to study the gene sequences that are complementary to cellular RNA. By this criterion expressed gene sequences are only 20-30% methylated. These data suggest that undermethylation is a general phenomenon in all actively transcribed genes.