Fernandez M, Olek A, Walter J, Sanchez J
Departamento de Biología Funcional e Instituto Universitario de Biotecnología de Asturias, Universidad de Oviedo, Spain.
Biol Chem. 1998 Apr-May;379(4-5):559-62.
5-Azacytidine inhibits DNA synthesis and to a lesser proportion RNA synthesis in S. antibioticus. The biosynthesis of proteins is not affected. The main inhibitory effect of 5-azacytidine on DNA and RNA synthesis is probably caused by its incorporation into newly synthesized DNA or RNA and the formation of covalent complexes between cytosine-specific methyltransferases and the modified DNA or RNA templates. To analyze whether such effects could occur at the oriC region of S. antibioticus we analyzed the methylation status of this region using the bisulphite assisted genomic sequencing method. One of the cytosine residues found to be partially methylated was contained within an unique NaeI sequence (GCCGGC) in oriC. Subsequent analysis shows chromosomal DNA from S. antibioticus to be resistant to R.NaeI restriction indicating that this strain contains a NaeI-specific cytosine C5-methyltransferase activity. Following 5-azacytidine treatment the NaeI site within the oriC region becomes partially demethylated. Our results suggest that some of the 5-azacytidine effects on DNA and RNA synthesis might indeed be related to the complex formation and inhibition of a cytosine-specific DNA methyltransferase.
5-氮杂胞苷抑制抗生链霉菌的DNA合成，对RNA合成的抑制作用较小。蛋白质的生物合成不受影响。5-氮杂胞苷对DNA和RNA合成的主要抑制作用可能是由于其掺入新合成的DNA或RNA中，以及胞嘧啶特异性甲基转移酶与修饰的DNA或RNA模板之间形成共价复合物所致。为了分析这种效应是否会在抗生链霉菌的oriC区域发生，我们使用亚硫酸氢盐辅助基因组测序方法分析了该区域的甲基化状态。在oriC中发现的一个部分甲基化的胞嘧啶残基位于一个独特的NaeI序列（GCCGGC）内。随后的分析表明，抗生链霉菌的染色体DNA对R.NaeI限制具有抗性，这表明该菌株具有NaeI特异性胞嘧啶C5-甲基转移酶活性。用5-氮杂胞苷处理后，oriC区域内的NaeI位点变得部分去甲基化。我们的结果表明，5-氮杂胞苷对DNA和RNA合成的一些影响可能确实与胞嘧啶特异性DNA甲基转移酶的复合物形成和抑制有关。
