Sunnerhagen P, Sjöberg R M, Bjursell G
Department of Medical Biochemistry, University of Göteborg, Sweden.
Somat Cell Mol Genet. 1989 Jan;15(1):61-70. doi: 10.1007/BF01534670.
We have analyzed the amount of extrachromosomal double-stranded covalently closed circular nonmitochondrial DNA in mouse 3T6 cells by Southern blotting and electron microscopy. Treatment with 7,1-dimethylbenz[a]anthracene, known to promote amplification of integrated SV40 genomes, elevated the amount of circular DNA. Inhibition of DNA synthesis with hydroxyurea, earlier shown to enhance amplification of the cellular dihydrofolate reductase gene, resulted in yet higher levels. Thus, elevation of the frequency of gene amplification and generation of extrachromosomal circular DNA seem to accompany each other in the situations studied in this paper. Two other DNA synthesis inhibitors, aphidicolin and thymidine, had markedly lesser effects on circular DNA. The significance of these findings for the mechanism of gene amplification is discussed.
我们通过Southern印迹法和电子显微镜分析了小鼠3T6细胞中染色体外双链共价闭合环状非线粒体DNA的量。用已知可促进整合的SV40基因组扩增的7,1-二甲基苯并[a]蒽处理，可提高环状DNA的量。用羟基脲抑制DNA合成，先前已证明其可增强细胞二氢叶酸还原酶基因的扩增，结果导致更高水平。因此，在本文研究的情况下，基因扩增频率的提高和染色体外环状DNA的产生似乎是相伴发生的。另外两种DNA合成抑制剂，阿非迪霉素和胸苷，对环状DNA的影响明显较小。讨论了这些发现对基因扩增机制的意义。
