Basnak'ian A G, Topol' L Z, Kirsanova I D, Votrin I I, Kiselev F L
Mol Biol (Mosk). 1989 May-Jun;23(3):750-7.
Activities of nuclear endonucleases and topoisomerase I were measured in rat fibroblasts which were at the stages of tumor transformation: control embryonal fibroblasts--CEF; cells immortalised by transfection of S1A segment of SA7 adenovirus--REF-1; intermedius cells transfected once by EJras oncogene--REF-1EJ; and cells transformed after the second transfection by the same oncogene--REF-2EJ. The topoisomerase I and Ca2+, Mg2+-dependent endonuclease was most decreased at the stage of immortalised cells, and the intermedius stage (REF-1EJ) was characterized by the lower activity of Ca2+, Mg2+-dependent endonuclease. The highest activity of Mn2+-dependent endonuclease is seen in REF-2EJ cells. In model experiments the ability of Ca2+, Mg2+-dependent endonuclease to split non-stochastically the EJras oncogene inserted into pBR322 plasmid was shown. The role of the investigated enzymes in the restriction of plasmid integration, cellular immortalisation and recombination of plasmids with chromosomes during cell transformation is discussed.
在处于肿瘤转化阶段的大鼠成纤维细胞中测定了核酸内切酶和拓扑异构酶I的活性：对照胚胎成纤维细胞——CEF；通过转染SA7腺病毒的S1A片段而永生化的细胞——REF-1；用EJras癌基因转染一次的中间细胞——REF-1EJ；以及用同一癌基因第二次转染后转化的细胞——REF-2EJ。拓扑异构酶I和Ca2+、Mg2+依赖性核酸内切酶在细胞永生化阶段下降最为明显，而中间阶段（REF-1EJ）的特征是Ca2+、Mg2+依赖性核酸内切酶活性较低。在REF-2EJ细胞中观察到Mn2+依赖性核酸内切酶的活性最高。在模型实验中，显示了Ca2+、Mg2+依赖性核酸内切酶非随机切割插入pBR322质粒的EJras癌基因的能力。讨论了所研究的酶在限制质粒整合、细胞永生化以及细胞转化过程中质粒与染色体重组中的作用。
