期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1981
卷号：78
期号：3
页码：1736-1740
DOI：10.1073/pnas.78.3.1736
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The state and organization of simian virus 40 (SV40) DNA in tsA mutant-transformed mouse clones were examined early after agar selection in an attempt to elucidate the mechanisms that actively generate the diverse integration patterns found in transformed cells. Although recently selected as a cloned population from agar, A21 cells displayed extremely heterogeneous SV40 DNA patterns when analyzed by agarose gel electrophoresis and Southern blot hybridization. Reselection of clones in agar from A21 at 33 degrees C or 39.5 degrees C and DNA analysis by hybridization demonstrated (i) simplification of the number of integration sites in the new clones; (ii) new sites of integrated SV40 DNA in high molecular weight cell DNA fragments generated by digestion with restriction endonuclease Bgl II; (iii) relatedness between clones with respect to integrated viral sequence arrangement; and (iv) persistence of free viral DNA forms. The majority of free viral DNA appeared to be full length, nondefective SV40 DNA, although a subpopulation of defective viral molecules was also detected. No detectable free SV40 DNA could be observed in A21 clonal derivatives isolated by growth in agar at 39.5 degrees C, indicating that the persistence of free viral forms was regulated by the A gene. These results suggest that the heterogeneity in viral sequences in the A21 cells was generated within a cloned population from which new clones can be derived with different transformed phenotypes and integration patterns.
