Stenzel-Poore M P, Rittenberg M B
J Immunol. 1987 May 1;138(9):3055-9.
We have found a novel immunoglobulin gene rearrangement in a murine hybridoma in which a heavy chain variable region (VH) heptamer-nonamer recognition sequence is joined to the diversity segment (D) through head-to-head fusion. The heptamer-nonamer recognition sequence and its adjacent 5' DNA are derived from the downstream flanking region of a germline VH gene. Sequence analysis indicates that this adjacent DNA is homologous to the downstream flank of VH108B, and it has characteristics of RNA processing that may suggest it was derived from an mRNA intermediate; these unusual features indicate that the segment is a processed gene. Because of head-to-head fusion, the recognition sequence and the flanking sequence are in opposite transcriptional polarity to D. The latter is joined correctly at its 3' border to a joining (J) gene segment. A gamma 1 constant region (but not mu) is located further downstream. Thus this fragment has several features common to normal immunoglobulin heavy chain gene rearrangement despite the unusual joining event involving V-D. Linkage of the VH heptamer-nonamer recognition sequence to D has not been observed previously. Although the recognition sequence described is inverted with respect to D and J, the endonucleolytic process that cleaved the recognition sequence at the 5' border of the heptamer before rearranging it to D was accurate. We suggest that of the three functions associated with the recombinase reaction; recognition, cutting, and ligation, only recognition and cutting may be limited to specific structures, and the ligation step may be less restricted because it is not confined to forming coding-to-coding or flank-to-flank joints. This aberrant ligation product suggests that the information leading to normal rearrangements may be found in structures that include more than the recognition sequences or coding regions alone, because the joining described here has spliced the incorrect end of a recognition sequence to a coding region to yield a nonproductive recombination.
我们在一个鼠杂交瘤中发现了一种新的免疫球蛋白基因重排，其中重链可变区（VH）七聚体-九聚体识别序列通过头对头融合与多样性区段（D）相连。七聚体-九聚体识别序列及其相邻的5' DNA源自种系VH基因的下游侧翼区域。序列分析表明，该相邻DNA与VH108B的下游侧翼同源，并且具有RNA加工的特征，这可能表明它源自mRNA中间体；这些不寻常的特征表明该区段是一个加工过的基因。由于头对头融合，识别序列和侧翼序列与D的转录极性相反。后者在其3'边界与连接（J）基因区段正确连接。一个γ1恒定区（而非μ恒定区）位于更下游。因此，尽管涉及V-D的连接事件不寻常，但该片段具有正常免疫球蛋白重链基因重排的几个共同特征。VH七聚体-九聚体识别序列与D的连接以前未被观察到。尽管所描述的识别序列相对于D和J是反向的，但在将识别序列重排至D之前，在七聚体的5'边界切割识别序列的内切核酸酶过程是准确的。我们认为，在与重组酶反应相关的三种功能中；识别、切割和连接，只有识别和切割可能限于特定结构，而连接步骤可能限制较少，因为它不限于形成编码到编码或侧翼到侧翼的接头。这种异常的连接产物表明，导致正常重排的信息可能存在于不仅包括识别序列或编码区的结构中，因为这里描述的连接将识别序列的错误末端拼接至编码区以产生无效重组。
