Claverys J P, Lefevre J C, Sicard A M
Proc Natl Acad Sci U S A. 1980 Jun;77(6):3534-8. doi: 10.1073/pnas.77.6.3534.
The genetic fate of a fragment of Streptococcus pneumoniae DNA cloned into a derivative of the Escherichia coli bacteriphage lambda has been studied in pneumococcal transformation. Transforming activity of this hybrid DNA is 8 times higher than standard S. pneumoniae DNA. Hybrid DNA is mutagenic for the recipient bacteria. Mutations are induced at a rate of 2 per 1000 transformation events. Most of these mutations are deletions adjacent to the cloned pneumococcal fragment, starting at or near its extremities and extending outside. The length of these deletions, estimated by genetic analysis or by gel electrophoresis of DNA fragments generated by restriction endonucleases, is quite variable, ranging from 150 base pairs to more than 1800 base pairs. Insertion of lambda DNA bas been detected in two large deletions by using DNAxDNA hybridization as a probe. This suggests that nonhomologous regions adjacent to the cloned fragment may be illegitimately integrated by the tranformation process. During the genetic analysis of these induced mutations we have observed that not only these deletions but also spontaneous deletions drastically increase recombination rates when present on donor DNA in transformation of neighboring markers. Such an effect is interpreted as partial exclusion of deletions from synapsis between donor and recipient DNA.
对克隆到大肠杆菌噬菌体λ衍生物中的肺炎链球菌DNA片段在肺炎球菌转化中的遗传命运进行了研究。这种杂交DNA的转化活性比标准肺炎链球菌DNA高8倍。杂交DNA对受体细菌具有致突变性。突变以每1000次转化事件2次的速率诱导产生。这些突变大多是与克隆的肺炎球菌片段相邻的缺失，从其末端或附近开始并向外延伸。通过遗传分析或限制性内切酶产生的DNA片段的凝胶电泳估计，这些缺失的长度变化很大，从150个碱基对到超过1800个碱基对不等。通过使用DNA-DNA杂交作为探针，在两个大的缺失中检测到了λDNA的插入。这表明与克隆片段相邻的非同源区域可能通过转化过程被非法整合。在对这些诱导突变的遗传分析过程中，我们观察到，当这些缺失存在于供体DNA上用于相邻标记的转化时，不仅这些缺失，而且自发缺失都会显著提高重组率。这种效应被解释为供体和受体DNA之间的联会对缺失的部分排斥。
