P NUCLEOTIDES IN V(D)J RECOMBINATION - A FINE-STRUCTURE ANALYSIS
P NUCLEOTIDES IN V(D)J RECOMBINATION - A FINE-STRUCTURE ANALYSIS
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DOI：
10.1128/mcb.13.2.1078
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发表时间：
1993-02-01
影响因子：
5.3
通讯作者：
LEWIS, SM
中科院分区：
文献类型：
--
作者：
MEIER, JT;LEWIS, SM
抗原受体基因在组装时从其组成部分获得连接插入，生殖系编码的V、D和J片段。镶件通常是随机顺序的，但少数V-D、D-J或V-J结点是例外的。在这样的连接中，一个或两个添加的碱基对反向重复毗邻的生殖系DNA的序列。(例如，以AG结尾的基因片段在连接时可能获得以残基CT开头的插入片段。)有人提出，被称为P核苷酸的非随机残基是V(D)J重组中强制性末端修饰步骤的结果。然而，在正常的、未选择的V(D)J连接产物中插入P还没有得到严格的证实。在这里，我们使用一个可实验操作的系统，从任何种类的免疫选择中分离出来，来检查在野生型淋巴样细胞中形成的V(D)J连接的精细结构。根据统计检验，我们的结果显示如下。(I)P插入的频率受连接端DNA序列的影响。(Ii)P插入片段的长度可长于两个残基。(Iii)P插入片段仅与编码末端相关。此外，对已发表的P核苷酸数据的系统调查显示，没有证据表明P插入作为遗传位点和个体发育的函数而发生变化。总之，这些分析确立了插入片段中P核苷酸模式的普遍性，但并不完全支持先前关于它们的起源和在连接反应中的中心性的猜想。
Antigen receptor genes acquire junctional inserts upon assembly from their component, germ line-encoded V, D, and J segments. Inserts are generally of random sequence, but a small number of V-D, D-J, or V-J junctions are exceptional. In such junctions, one or two added base pairs inversely repeat the sequence of the abutting germ line DNA. (For example, a gene segment ending AG might acquire an insert beginning with the residues CT upon joining.) It has been proposed that the nonrandom residues, termed ''P nucleotides,'' are a consequence of an obligatory end-modification step in V(D)J recombination. P insertion in normal, unselected V(D)J joining products, however, has not been rigorously established. Here, we use an experimentally manipulable system, isolated from immune selection of any kind, to examine the fine structure of V(D)J junctions formed in wild-type lymphoid cells. Our results, according to statistical tests, show the following. (i) The frequency of P insertion is influenced by the DNA sequence of the joined ends. (ii) P inserts may be longer than two residues in length. (iii) P inserts are associated with coding ends only. Additionally, a systematic survey of published P nucleotide data shows no evidence for variation in P insertion as a function of genetic locus and ontogeny. Together, these analyses establish the generality of the P nucleotide pattern within inserts but do not fully support previous conjectures as to their origin and centrality in the joining reaction.