The effect of site specific methylation on restriction endonuclease digestion.
The effect of site specific methylation on restriction endonuclease digestion.
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位点特异性甲基化对限制性内切酶消化的影响。
DOI：
10.1093/nar/13.suppl.r201
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发表时间：
1985
影响因子：
14.9
通讯作者：
M. Nelson
中科院分区：
文献类型：
--
作者：
Michael McClelland;M. Nelson
自上次编译以来，在位点特异性DNA甲基化领域有了许多重要的新进展（48）。已经开发了在8、10和可能在12或14个碱基对序列上产生限制性内切酶切割的方法（49）。该技术依赖于位点特异性甲基化酶和甲基化依赖性限制。唯一已知的甲基化依赖性限制系统是Dpn I （GmATC）及其同分异构体。然而，大肠杆菌的DNA是检测内切酶的常用底物，除了GmATC和CmC(A/T)GG外，其他DNA都没有甲基化。因此，很可能存在其他甲基化依赖的内切酶，这些内切酶还没有被这种底物检测到。Nelson等人研究了大量限制性内切酶修饰甲基化酶作为限制性内切酶的阻断剂（52）。在核酸内切酶识别序列上部分重叠和阻断切割的甲基化酶特异性提供了既新颖又罕见的限制性特异性。例如，Nae I （GCCGGC）位点的一个子集GGCCGGC和GCCGGCC被M.Hae III （GGmCC）阻断。因此，Nae I在M.Hae III甲基化DNA中的特异性为（A/C/T）GCCGGC（A/G/T）。在胞嘧啶N-4位甲基化的M.Bcn I （CC(C/G)GG）中发现了一种新的修饰甲基化酶特异性（30）。已知来自亲缘物种的Bst NI （CC(A/T)GG）在其识别序列中任何胞嘧啶组合的C-5位置切割甲基化的DNA。看起来M.Bst NI也是一个
INTRODUCTION There have been a number of important new developments in the field of site specific DNA methylation since the last compilation (48). A method for producing restriction endonuclease cleavage at 8, 10 and potentially at 12 or 14 base pair sequences has been developed (49). The technique relies on site specific methylases and methylation dependent restriction. The only methylation dependent restriction systems known are Dpn I (GmATC) and its isoschizomers. However, DNA from E.coli, which is the usual substrate for assaying endonucleases, is unmethylated except at GmATC and CmC(A/T)GG. Thus, it is likely that there are other methylation dependent endonucleases which have not been detected with this substrate. Nelson et al have investigated a large number of restriction modification methylases as blocking agents for restriction endonucleases (52). Methylase specificities which partly overlap and block cleavage at endonuclease recognition sequences give restriction specificities which are both novel and rarer. For example, a subset of Nae I (GCCGGC) sites, GGCCGGC and GCCGGCC, are blocked by M.Hae III (GGmCC). The specificity of Nae I is thus (A/C/T)GCCGGC(A/G/T) in M.Hae III methylated DNA. A new type of modification methylase specificity has been found for M.Bcn I (CC(C/G)GG) which methylates at the N-4 position of cytosine (30). Bst NI (CC(A/T)GG) from a related species is known to cut DNA that is methylated at the C-5 position of cytosine at any combination of cytosines in its recognition sequence. It seems likely that M.Bst NI is also an