Analysis of extrachromosomal DNA from normal and tumor cells

Two independent methods (pulse-electrophoresis of intact DNA isolated from agarose-encapsulated cells and differential extraction of intact DNA from Celite-immobilized nucleoproteins) yielded evidence of the presence of free (extrachromosomal) DNA in cells of various origin, both malignant and normal, cultured and isolated from animal tissues. Free DNA from all cell types studied form three discrete electrophoretic bands of 400, 250–300, and 50 thousand base pairs. According to the data on³H-thymidine incorporation, free and chromosomal DNA differ in their metabolic properties. By means of the polymerase chain reaction using c-myc and L-myc primers it is established that free DNAs of HT1080 cells contain structural genes. Application of the method of conformational polymorphism of single-strand fragments revealed their identity to the corresponding genes localized in the chromosomes. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, No 5, pp. 533–536, May, 1995 Presented by I. P. Ashmarin, Member of the Russian Academy of Medical Sciences