Targeting of the activation-induced cytosine deaminase is strongly influenced by the sequence and structure of the targeted DNA.
Targeting of the activation-induced cytosine deaminase is strongly influenced by the sequence and structure of the targeted DNA.
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激活诱导的胞嘧啶脱氨酶的靶向很大程度上受到靶 DNA 的序列和结构的影响。
DOI：
10.1128/mcb.25.24.10815-10821.2005
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Storb,Ursula
中科院分区：
文献类型：
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作者：
Shen,HongMing;Ratnam,Sarayu;Storb,Ursula
活化诱导的脱氨酶（AID）启动免疫球蛋白体细胞超突变（SHM）。由于体外AID显示出对单链DNA或非转录链上的胞嘧啶脱氨基，因此体内AID如何同等地靶向两条DNA链仍然是一个谜。在这里，我们调查的作用，转录和DNA序列的胞嘧啶脱氨。用不同的底物发现了显著不同的结果。根据靶序列，转录的DNA链与非转录链一样或更好地被靶向。优先选择目标与艾滋病热点的频率无关。AID和亚硫酸氢盐对胞嘧啶脱氨基作用的比较显示出不同的靶向模式，表明AID可以局部解旋DNA。我们的结论是，体细胞超突变的两个DNA链上的AID行动转录基因的自然结果，此外，DNA序列或结构和拓扑结构发挥主要作用，在体外和体内靶向AID。另一方面，在SHM期间，免疫球蛋白基因启动子的前100个核苷酸和超过约1至2kb的突变的缺乏必须是由于体内转录和染色质的特殊条件。
Activation-induced deaminase (AID) initiates immunoglobulin somatic hypermutation (SHM). Since in vitro AID was shown to deaminate cytosines on single-stranded DNA or the nontranscribed strand, it remained a puzzle how in vivo AID targets both DNA strands equally. Here we investigate the roles of transcription and DNA sequence in cytosine deamination. Strikingly different results are found with different substrates. Depending on the target sequence, the transcribed DNA strand is targeted as well as or better than the nontranscribed strand. The preferential targeting is not related to the frequency of AID hot spots. Comparison of cytosine deamination by AID and bisulfite shows different targeting patterns suggesting that AID may locally unwind the DNA. We conclude that somatic hypermutation on both DNA strands is the natural outcome of AID action on a transcribed gene; furthermore, the DNA sequence or structure and topology play major roles in targeting AID in vitro and in vivo. On the other hand, the lack of mutations in the first ∼100 nucleotides and beyond about 1 to 2 kb from the promoter of immunoglobulin genes during SHM must be due to special conditions of transcription and chromatin in vivo.