Specific Inhibitory Effect of H1e Histone Somatic Variant onin VitroDNA-Methylation Process
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文摘
H1e and H1c histone variants were purified from mouse L929 fibroblasts using a reverse phase HPLC, and their effect onin vitroDNA methylation was investigated, together with their ability to bind unmethylated or methylated CpG-rich 44bp oligonucleotides. In a “physiological” range of H1:DNA ratios, only H1e, at variance from H1c, was found to cause a marked inhibition ofin vitroenzymic DNA methylation. It was also shown that both variants have a similar affinity in binding a methylated CpG-rich oligonucleotide, but that the binding to the same oligonucleotide in the unmethylated form occurs preferentially with H1e rather than with H1c. H1e is therefore likely to be directly involved in maintaining CpG-rich sequences in the unmethylated state.