Mel'nikov A L, Vel'kov V V, Fodor I I
Genetika. 1981;17(1):45-51.
The stability of hybrid plasmids, constructed on the basis of vector pCV20(AprTcr) and containing HindIII fragments of Drosophila melanogaster DNA (pDm6, pDm9) and PstI fragments of D. melanogaster DNA (pDm39, pDm187, pDm189) was studied. After the transformation of E. coli HB101 recA and Escherichia coli 802 rec+ and selection to Tcr (pDm6, pDm9), or to Apr (pDm39, pDm189, pDm187) 0.04--9% of clones with reduced resistance to Tc or Ap was detected. The hybrid plasmids are more stable in rec-, but not in rec+ strain, the stability depends of the nature of cloned DNA, and on the site of vector DNA in which foreign genes are cloned. Restriction endonuclease analysis revealed that all plasmids of the clones with reduced Tcr or Apr lost the inserted DNA and the excision of foreign DNA occurred precisely in the sites of cloning. We suggest that the genome of the hybrid plasmid in the region of foreign insertion has a conformation which allows the bringing together the ends of cloned DNA with the following excision of the foreign genes.
研究了基于载体pCV20(AprTcr)构建的、含有黑腹果蝇DNA的HindIII片段（pDm6、pDm9）和PstI片段（pDm39、pDm187、pDm189）的杂种质粒的稳定性。用杂种质粒转化大肠杆菌HB101 recA和大肠杆菌802 rec+，并筛选对Tcr（pDm6、pDm9）或Apr（pDm39、pDm189、pDm187）有抗性的菌株，结果发现0.04% - 9%的克隆对Tc或Ap的抗性降低。杂种质粒在rec-菌株中更稳定，而在rec+菌株中则不然，其稳定性取决于克隆DNA的性质以及外源基因克隆到载体DNA的位点。限制性内切酶分析表明，所有对Tcr或Apr抗性降低的克隆的质粒都失去了插入的DNA，外源DNA的切除恰好发生在克隆位点。我们认为，杂种质粒在外源插入区域的基因组具有一种构象，这种构象允许克隆DNA的末端聚集在一起，随后切除外源基因。
