RNase and alkali sensitivity of closed circular mitochondrial DNA of rat ascites hepatoma cells

Abstract
A preparation of the closed circular DNA duplex was obtained from whole rat ascites hepatoma cells, AH66, by lysis of cells with SDS and purification by CsCl-dye buoyant-density centrifugation. RNase A converted the closed circular mitochondrial DNA to open circular molecules. The closed circular DNA was also sensitive to alkali. The conversion to the open form was shown from the results of centrifugal analyses on neutral and alkaline sucrose density gradients and CsCl-ethidium bromide. These results indicate the presence of at least one RNA region in closed circular double stranded mitochondrial DNA.