Jeddeloh J A, Richards E J
Department of Biology, Washington University, St. Louis, MO 63130, USA.
Plant J. 1996 May;9(5):579-86. doi: 10.1046/j.1365-313x.1996.9050579.x.
Two different methods were used to investigate the abundance of cytosine methylation at the outer (5') position in 5'-CCG-3' trinucleotides in angiosperm genomes. Mspl is unable to cut its target site if the outer cytosine is methylated (5'-mCCGG-3'). Using Mspl restriction analysis, it was shown that 5'-mCCG-3' is present in all angiosperm genomes examined, and that the amount of cytosine methylation at this site varies between species. Subsequently, direct measurements were made of the amount of methylation at both cytosines in a subset of 5'-CCG-3' trinucleotides in the Arabidopsis thaliana genome. Based upon these analyses, it was estimated that approximately 20-30% of 5'-CCG-3' trinucleotides in A. thaliana are methylated at the outer cytosine. Approximately 20% of the 5'-CCG-3' trinucleotides contain 5-methyl-cytosine at the inner cytosine position, which corresponds to a previous determination of 5'-mCG-3' methylation in A. thaliana. The implications of 5'-mCCG-3' methylation are discussed.
采用两种不同方法研究被子植物基因组中5'-CCG-3'三核苷酸外侧（5'）胞嘧啶甲基化的丰度。如果外侧胞嘧啶发生甲基化（5'-mCCGG-3'），MspI就无法切割其靶位点。利用MspI限制性分析表明，在所检测的所有被子植物基因组中均存在5'-mCCG-3'，且该位点的胞嘧啶甲基化量在不同物种间存在差异。随后，对拟南芥基因组中一部分5'-CCG-3'三核苷酸的两个胞嘧啶的甲基化量进行了直接测量。基于这些分析，估计拟南芥中约20%-30%的5'-CCG-3'三核苷酸在外侧胞嘧啶处发生甲基化。约20%的5'-CCG-3'三核苷酸在内侧胞嘧啶位置含有5-甲基胞嘧啶，这与之前对拟南芥中5'-mCG-3'甲基化的测定结果相符。本文讨论了5'-mCCG-3'甲基化的意义。
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