Besmer Eva, Market Eleonora, Papavasiliou F Nina
Laboratory of Lymphocyte Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
Mol Cell Biol. 2006 Jun;26(11):4378-85. doi: 10.1128/MCB.02375-05.
Activation-induced cytidine deaminase (AID) is a single-stranded DNA deaminase required for somatic hypermutation of immunoglobulin (Ig) genes, a key process in the development of adaptive immunity. Transcription provides a single-stranded DNA substrate for AID, both in vivo and in vitro. We present here an assay which can faithfully replicate all of the molecular features of the initiation of hypermutation of Ig genes in vivo. In this assay, which detects AID-mediated deamination in the context of transcription by Escherichia coli RNA polymerase, deamination targets either strand and declines in efficiency as the distance from the promoter increases. We show that AID binds DNA exposed by the transcribing polymerase, implicating the polymerase itself as the vehicle which distributes AID on DNA as it moves away from the promoter.
激活诱导的胞嘧啶脱氨酶（AID）是一种单链DNA脱氨酶，是免疫球蛋白（Ig）基因体细胞超突变所必需的，而体细胞超突变是适应性免疫发育中的关键过程。无论是在体内还是体外，转录都为AID提供单链DNA底物。我们在此展示一种检测方法，它能够如实地复制体内Ig基因超突变起始的所有分子特征。在该检测方法中，通过大肠杆菌RNA聚合酶在转录背景下检测AID介导的脱氨作用，脱氨作用可靶向任一条链，并且随着与启动子距离的增加，效率会降低。我们发现AID结合由转录聚合酶暴露的DNA，这表明聚合酶本身就是在其远离启动子移动时将AID分布于DNA上的载体。
