Repair of lesions induced by bruneomycin in DNA of isolated mitochondria from the mature eggs of the teleost fish Misgurnus fossilis.

Addition of a radiomimetic antibiotic bruneomycin (Streptonigrin) to isolated mitochondria from mature quiescent oocytes of the teleost fish loach Misgurnus fossilis leads to the induction of unscheduled synthesis of mitochondrial DNA. Most of the newly synthesized DNA has the sedimentation properties of open circles and up to 15% of the label is present in the fraction of the covalently closed-circular molecules. The size of the newly synthesized DNA stretches determined from the bouyant shift of DNA labeled with 5-bromouracil and [3H]dAMP and sonicated to fragments of different molecular weight, was found to be equal to about 1000 nucleotides for the labeled covalently closed circles and to about 2000 nucleotides for the labeled open-circular DNA. Experiments with the centrifugation of non-sheared and sonicated 5-bromouracil and [3H]dAMP-labeled mitochondrial DNA (mtDNA) in alkaline CsCl density gradients provided evidence of a covalent linkage between newly-synthesized stretches and the parental DNA strands. It is concluded from these data that the unscheduled mtDNA synthesis induced by bruneomycin does at least in part represent mtDNA repair synthesis.