MITOCHRONDRIA-ASSOCIATED RIBONUCLEIC ACID OF HELA CELL . EFFECT OF ETHIDIUM BROMIDE ON SYNTHESIS OF RIBOSOMAL AND 4S RIBONUCLEIC ACID

The synthesis of the two electrophoretic classes of 4S ribonucleic acid associated with HeLa mitochondria is inhibited by ethidium bromide. The synthesis of the mitochondria-associated 28S and 5S ribosomal ribonucleic acid and the synthesis of the cytoplasmic 28S, 18S, and 5S ribosomal ribonucleic acid and cytoplasmic 4S ribonucleic acid are unaffected by ethidium bromide under identical conditions. The methylation of the two classes of mitochondriaassociated 4S ribonucleic acid is significantly different from the methylation of the cytoplasmic 4S ribonucleic acid. It is suggested that the mitochondria-associated 4S ribonucleic acid is transcribed from the mitochondrial deoxyribonucleic acid and that the 28S and 5S ribosomal ribonucleic acid in the mitochondrial fraction may be from the cytoplasm and of nuclear origin. © 1969, American Chemical Society. All rights reserved.