Ott T, Nelsen-Salz B, Döring H P
Institute of Genetics, Universität zu Köln, Germany.
Plant J. 1992 Sep;2(5):705-11.
The maize transposable element Activator (Ac) carries subterminal CpG-rich sequences which are essential for the transposition of the element. It has previously been shown that the methylation of certain sequences contained in this region can alter their ability to interact with the Ac-encoded protein. The novel hypothesis that the methylation of subterminal Ac sequences is required for transposition was tested. Approximately 150 bp of the 5' subterminal region of the Ac element was examined for the presence of 5-methylcytosines by the ligation-mediated polymerase chain reaction (LMPCR)-aided genomic sequencing method. The methylation status of 22 and 39 cytosines on either strand of the DNA were analysed in each of five different transgenic tobacco cultures carrying transposable Ac sequences. Ten micrograms of tobacco DNA were used for each base-specific cleavage reaction before amplification by LMPCR. All but one of the cytosines were unmethylated. Only a minor fraction of the Ac molecules was methylated at one cytosine residue. It is concluded that DNA methylation at the tested Ac sequences is not required for the transposability of Ac or Ds elements in tobacco cells.
玉米转座因子激活子（Ac）携带亚末端富含CpG的序列，这些序列对于该因子的转座至关重要。此前已经表明，该区域中某些序列的甲基化会改变它们与Ac编码蛋白相互作用的能力。我们对转座需要亚末端Ac序列甲基化这一新假说进行了验证。通过连接介导的聚合酶链反应（LMPCR）辅助基因组测序方法，检测了Ac因子5'亚末端区域约150 bp的序列中5-甲基胞嘧啶的存在情况。在携带可转座Ac序列的五种不同转基因烟草培养物中，分别分析了DNA每条链上22个和39个胞嘧啶的甲基化状态。在通过LMPCR扩增之前，每次碱基特异性切割反应使用10微克烟草DNA。除一个胞嘧啶外，所有胞嘧啶均未甲基化。只有一小部分Ac分子在一个胞嘧啶残基处发生了甲基化。得出的结论是，烟草细胞中Ac或Ds因子的转座能力并不需要所检测的Ac序列发生DNA甲基化。
