摘要：

We have studied the effect of DNA methylation on human γ-globin gene expression, using a novel in vitro DNA methylation technique. With this method we have methylated specific segments of the γ-globin gene and its 5′-flanking region, which were cloned for this purpose in the bacteriophage vector M13mp8. The in vitro methylated DNA was introduced into mouse L-cells by cotransfer using the herpes simplex virus thymidine kinase gene as a selective marker. Transformed cell lines were isolated to examine the inheritance of the segmental methylation pattern and its effect on the expression of the γ-globin gene. Cells transformed with DNA methylated throughout the M13 vector and γ-globin DNA sequences do not express the γ-globin gene. Methyl-C residues in either the M13 DNA sequences or the γ-globin structural gene have, however, no inhibitory effect on globin transcription. In contrast, methylation in the 5′ region of the γ-globin gene (from nucleotides −760 to +100) prevents transcription. These data indicate that DNA methylation in the 5′ region of a gene might play a direct role in the regulation of gene expression.

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