Harrington J, Hsieh C L, Gerton J, Bosma G, Lieber M R
Department of Pathology, Stanford University School of Medicine, California 94305-5324.
Mol Cell Biol. 1992 Oct;12(10):4758-68. doi: 10.1128/mcb.12.10.4758-4768.1992.
Murine severe combined immune deficiency (scid) is marked by a 5,000-fold reduction in coding joint formation in V(D)J recombination of antigen receptors. Others have demonstrated a sensitivity to double-strand breaks generated by ionizing radiation and bleomycin. We were interested in establishing the extent of the defect in intramolecular and intermolecular DNA end joining in lymphoid and nonlymphoid cells from scid mice. We conducted a series of studies probing the ability of these cells to resolve free ends of linear DNA molecules having various biochemical end configurations. We find that the stable integration of linear DNA into scid fibroblasts is reduced 11- to 75-fold compared with that in normal fibroblasts. In contrast, intramolecular and intermolecular end joining occur at normal frequencies in scid lymphocytes and fibroblasts. This normal level of end joining is observed regardless of the type of overhang and regardless of the requirement for nucleolytic activities prior to ligation. The fact that free ends having a wide variety of end configurations are recircularized normally in scid cells rules out certain models for the defect in scid. We discuss the types of DNA end joining reactions that are and are not affected in this double-strand break repair defect in the context of a hairpin model for V(D)J recombination.
小鼠严重联合免疫缺陷（scid）的特征是抗原受体V（D）J重组中编码接头形成减少5000倍。其他人已经证明scid小鼠对电离辐射和博来霉素产生的双链断裂敏感。我们感兴趣的是确定scid小鼠的淋巴细胞和非淋巴细胞中分子内和分子间DNA末端连接缺陷的程度。我们进行了一系列研究，探究这些细胞解决具有各种生化末端构型的线性DNA分子自由末端的能力。我们发现，与正常成纤维细胞相比，线性DNA稳定整合到scid成纤维细胞中的效率降低了11至75倍。相比之下，scid淋巴细胞和成纤维细胞中分子内和分子间的末端连接以正常频率发生。无论突出端的类型如何，也无论连接前对核酸水解活性的要求如何，都能观察到这种正常水平的末端连接。scid细胞中具有多种末端构型的自由末端能正常环化，这一事实排除了某些关于scid缺陷的模型。我们在V（D）J重组的发夹模型背景下，讨论了在这种双链断裂修复缺陷中受影响和不受影响的DNA末端连接反应类型。
