Harland R M
Proc Natl Acad Sci U S A. 1982 Apr;79(7):2323-7. doi: 10.1073/pnas.79.7.2323.
Plasmid DNA methylated at Hpa II sites was injected into eggs of Xenopus laevis. The methylated DNA replicates extrachromosomally, and the methylated state of the H pa II sites is inherited through replication. Unmethylated sites remain unmethylated in progeny molecules. To test whether replication is necessary for new methylation to occur, DNA methylated on one strand only was injected and unreplicated DNA was selected for analysis. Methylation was copied onto a previously unmethylated strand in the absence of replication but less efficiently than in its presence. These experiments show that the individual methylated site contains enough information for inheritance of the methylated state and that inheritance of methylation does not require integration of the DNA into the chromosome.
在Hpa II位点甲基化的质粒DNA被注入非洲爪蟾的卵中。甲基化的DNA进行染色体外复制，并且Hpa II位点的甲基化状态通过复制得以遗传。未甲基化的位点在子代分子中保持未甲基化状态。为了测试复制对于新的甲基化发生是否必要，仅对一条链甲基化的DNA被注入，并选择未复制的DNA进行分析。在没有复制的情况下，甲基化被复制到先前未甲基化的链上，但效率低于有复制的情况。这些实验表明，单个甲基化位点包含足够的信息用于甲基化状态的遗传，并且甲基化的遗传不需要将DNA整合到染色体中。
