Replacement of 5-methylcytosine by cytosine: a possible mechanism for transient DNA demethylation during differentiation.
Replacement of 5-methylcytosine by cytosine: a possible mechanism for transient DNA demethylation during differentiation.
复制标题
胞嘧啶取代 5-甲基胞嘧啶：分化过程中短暂 DNA 去甲基化的可能机制。
DOI：
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发表时间：
1986
影响因子：
11.1
通讯作者：
G. Cantoni
中科院分区：
文献类型：
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作者：
A. Razin;M. Szyf;T. Kafri;M. Roll;H. Giloh;S. Scarpa;D. Carotti;G. Cantoni
在早期的一项研究中，人们发现，当Friend红白血病细胞（FELC）暴露于各种能够诱导分化的化学试剂时，它们的DNA发生了全基因组的瞬时去甲基化。在试图阐明负责这种现象的生化机制，我们诱导FELC与5 mM的六亚甲基双乙酰胺和标记的DNA在体内的密度标签，5-溴脱氧尿苷，和放射性标记，脱氧[5- 3 H]胞苷。通过等密度离心将新复制的DNA（重-轻）与亲本DNA（轻-轻）分离。仅在诱导细胞中观察到脱氧[5- 3 H]胞苷掺入光-光双链体DNA中，同时伴有DNA的去甲基化，而在平行实验中，脱氧[G-3 H]腺苷未掺入光-光DNA中。还发现，用脱氧[5- 3 H]胞苷标记轻-轻DNA是短暂的，因为在去甲基化之后的从头DNA甲基化期间，3 H标记从DNA中除去。综合这些结果，有力地表明，分化过程中DNA的去甲基化是通过酶促机制实现的，其中5-甲基胞嘧啶被胞嘧啶取代。
In an earlier study it was discovered that when Friend erythroleukemia cells (FELC) were exposed to a variety of chemical agents capable of inducing differentiation, their DNA underwent genome-wide transient demethylation. In an attempt to elucidate the biochemical mechanism responsible for this phenomenon we have induced FELC with 5 mM hexamethylenebisacetamide and labeled the DNA in vivo with a density label, 5-bromodeoxyuridine, and a radioactive label, deoxy[5-3H]cytidine. Newly replicated DNA (heavy-light) was separated from parental DNA (light-light) by isopycnic centrifugation. Incorporation of deoxy[5-3H]cytidine into light-light duplex DNA has been observed only in induced cells concomitantly with the demethylation of the DNA, whereas, in parallel experiments, deoxy[G-3H]adenosine was not incorporated into light-light DNA. It was also found that the labeling of light-light DNA with deoxy[5-3H]cytidine is transient since the 3H label was removed from the DNA during the period of de novo DNA methylation that follows the demethylation. These results, taken together, strongly suggest that the demethylation of the DNA during differentiation is achieved by an enzymatic mechanism whereby 5-methylcytosine is replaced by cytosine.