Wilkinson C R, Bartlett R, Nurse P, Bird A P
Institute of Cell and Molecular Biology, University of Edinburgh, UK.
Nucleic Acids Res. 1995 Jan 25;23(2):203-10. doi: 10.1093/nar/23.2.203.
DNA methylation of cytosine residues is a widespread phenomenon and has been implicated in a number of biological processes in both prokaryotes and eukaryotes. This methylation occurs at the 5-position of cytosine and is catalyzed by a distinct family of conserved enzymes, the cytosine-5 methyltransferases (m5C-MTases). We have cloned a fission yeast gene pmt1+ (pombe methyltransferase) which encodes a protein that shares significant homology with both prokaryotic and eukaryotic m5C-MTases. All 10 conserved domains found in these enzymes are present in the pmt1 protein. This is the first m5C-MTase homologue cloned from a fungal species. Its presence is surprising, given the inability to detect DNA methylation in yeasts. Haploid cells lacking the pmt1+ gene are viable, indicating that pmt1+ is not an essential gene. Purified, bacterially produced pmt1 protein does not possess obvious methyltransferase activity in vitro. Thus the biological significance of the m5C-MTase homologue in fission yeast is currently unclear.
胞嘧啶残基的DNA甲基化是一种普遍现象，在原核生物和真核生物的许多生物学过程中都有涉及。这种甲基化发生在胞嘧啶的5位，由一类独特的保守酶——胞嘧啶-5甲基转移酶（m5C-MTases）催化。我们克隆了一个裂殖酵母基因pmt1+（粟酒裂殖酵母甲基转移酶），它编码的蛋白质与原核和真核m5C-MTases都有显著的同源性。这些酶中发现的所有10个保守结构域都存在于pmt1蛋白中。这是从真菌物种中克隆的第一个m5C-MTase同源物。鉴于在酵母中无法检测到DNA甲基化，它的存在令人惊讶。缺乏pmt1+基因的单倍体细胞是有活力的，这表明pmt1+不是一个必需基因。在体外，经细菌产生并纯化的pmt1蛋白不具有明显的甲基转移酶活性。因此，裂殖酵母中m5C-MTase同源物的生物学意义目前尚不清楚。
