Novel non-specific DNA adenine methyltransferases
Novel non-specific DNA adenine methyltransferases
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DOI：
10.1093/nar/gkr1039
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发表时间：
2012-03-01
影响因子：
14.9
通讯作者：
Radlinska, Monika
中科院分区：
文献类型：
--
作者：
Drozdz, Marek;Piekarowicz, Andrzej;Radlinska, Monika
噬菌体Mu的mom基因编码一种酶，该酶将噬菌体DNA中的腺嘌呤转化为N-6-（1-乙酰氨基）-腺嘌呤，从而保护病毒基因组免受各种限制性内切酶的切割。Mu样原噬菌体序列存在于流感嗜血杆菌Rd（FluMu）、脑膜炎奈瑟菌A型菌株Z2491（Pnme 1）和H.流感生物型埃及伊蚊ATCC 11116不具有Mom编码基因。相反，在Mu中由mom占据的位置，它们携带一个不相关的基因，该基因编码与DNA腺嘌呤N-6-甲基转移酶同源的蛋白质（分别为hin 1523，nma 1821，hia 5）。hin 1523、hia 5和nma 1821基因的产物在体外和体内均将腺嘌呤残基修饰为N-6-甲基腺嘌呤。所有这些酶都催化了广泛的DNA甲基化;最值得注意的是Hia 5蛋白导致了λ DNA中61%的腺嘌呤甲基化。寡核苷酸甲基化的动力学分析表明，DNA中的所有腺嘌呤残基，与可能的例外聚（A）-tracts，构成底物的Hia 5和Hin 1523酶。它们潜在的“序列特异性”可概括为AB或BA（其中B = C、G或T）。从大肠杆菌细胞中分离的质粒DNA过表达这些新的DNA甲基转移酶是耐切割的许多限制性内切酶敏感的腺嘌呤甲基化。
The mom gene of bacteriophage Mu encodes an enzyme that converts adenine to N-6-(1-acetamido)-adenine in the phage DNA and thereby protects the viral genome from cleavage by a wide variety of restriction endonucleases. Mu-like prophage sequences present in Haemophilus influenzae Rd (FluMu), Neisseria meningitidis type A strain Z2491 (Pnme1) and H. influenzae biotype aegyptius ATCC 11116 do not possess a Mom-encoding gene. Instead, at the position occupied by mom in Mu they carry an unrelated gene that encodes a protein with homology to DNA adenine N-6-methyltransferases (hin1523, nma1821, hia5, respectively). Products of the hin1523, hia5 and nma1821 genes modify adenine residues to N-6-methyladenine, both in vitro and in vivo. All of these enzymes catalyzed extensive DNA methylation; most notably the Hia5 protein caused the methylation of 61% of the adenines in lambda DNA. Kinetic analysis of oligonucleotide methylation suggests that all adenine residues in DNA, with the possible exception of poly(A)-tracts, constitute substrates for the Hia5 and Hin1523 enzymes. Their potential 'sequence specificity' could be summarized as AB or BA (where B = C, G or T). Plasmid DNA isolated from Escherichia coli cells overexpressing these novel DNA methyltransferases was resistant to cleavage by many restriction enzymes sensitive to adenine methylation.