Antequera F, Tamame M, Vilanueva J R, Santos T
Nucleic Acids Res. 1985 Sep 25;13(18):6545-58. doi: 10.1093/nar/13.18.6545.
DNA methylation is a rather sparse event among fungi. Phycomyces blakesleeanus seems to be one of the few exceptions in this context. 5-Methylcytosine represents 2.9% of the total cytosine in spore DNA and is located in approximately the same amount at any of the four CA, CT, CC or CG dinucleotides. A progressive and gradual drop in total 5-methylcytosine parallels the development of the fungus. This demethylation is non random but sequence specific and is not accounted for equally by the four different methylated dinucleotides, CG being much less affected (20% demethylated) than CA, CT and CC (more than 90% demethylated at the same time). "De novo" methylation to restore the initial pattern probably takes place during spore maturation. By using specific hybridization probes we have been able to show that the rRNA genes are not significantly methylated at any stage of development, regardless of their transcription status.
DNA甲基化在真菌中是一个相当罕见的现象。在这种情况下，布氏梨形孢似乎是少数几个例外之一。5-甲基胞嘧啶占孢子DNA中总胞嘧啶的2.9%，并且在四个二核苷酸CA、CT、CC或CG中的任何一个中含量大致相同。真菌发育过程中，总5-甲基胞嘧啶含量逐渐下降。这种去甲基化不是随机的，而是序列特异性的，并且四种不同的甲基化二核苷酸对其影响并不相同，CG受影响程度远小于CA、CT和CC（CG去甲基化20%，而CA、CT和CC同时去甲基化超过90%）。“从头”甲基化以恢复初始模式可能发生在孢子成熟过程中。通过使用特异性杂交探针，我们已经能够证明，无论rRNA基因的转录状态如何，其在发育的任何阶段都没有明显甲基化。
