The Number of Mitochondrial Deoxyribonucleic Acid Genomes in Mouse L and Human HeLa Cells

Abstract

Abstract Mitochondrial DNA can be isotopically labeled to the virtual exclusion of nuclear DNA labeling in cell lines lacking the major soluble thymidine kinase (EC 2.7.1.21) but retaining a mitochondrial thymidine kinase. This characteristic provides a means for the selective assay of mitochondrial DNA during isolation and a determination of the cellular content of mitochondrial DNA. The simplest of the three isolation procedures compared in this study is shown to yield approximately two-thirds of the total mitochondrial DNA in the tissue culture cells examined. Mouse L cells containing predominantly a 107 dalton closed circular mitochondrial DNA species have 1100 ± 250 molecules per cell. A second line of mouse L cells which has mitochondrial DNA of molecular weight 2 x 107 contains approximately 900 molecules per cell. HeLa cells have at least four times the mitochondrial DNA mass per mitochondrial volume as L cells.