Poly(adenylic acid) synthesis in isolated rat liver mitochondria

Abstract

Purified rat liver mitochondria were shown to synthesize poly(adenylic acid) [poly(A)] in vitro. Detection of the poly(A) synthesizing activity was facilitated by addition of NaF to the reaction mixture. The product of the reaction was shown to be poly(A) by its insensitivity to digestion with pancreatic RNase and RNase T1, its degradation by [viper] venom phosphodiesterase and its retention on poly(uridylic acid) cellulose columns. The average chain length of the product was 20-23 AMP units and it was covalently attached to the endogenous RNA in the mitochondria. Poly(A) synthesis required ATP and a divalent ion and was maximally active in the pH range of 7-8. The reaction was inhibited by atractyloside, cordycepin triphosphate, Rose Bengal, rifamycin derivative AF/013 [3-formyl-rifamycin-SV-O-n-octyloxime], sodium pyrophosphate and N-ethylmaleimide. It was indicated that mitochondrial poly(A) polymerase is probably involved in the posttranscriptional addition of poly(A) sequence to mitochondrial RNA.