Primer directed poly(A) synthesis in rat liver mitochondria

Rat liver mitochondria contain an endogenous factor highly specific in stimulating the homologous poly(A) polymerase. By using an $\text{in vivo}$ labelling with [³²P] orthophosphate it is possible to prepare a labelled factor and to demonstrate that it is stably incorporated in an acid insoluble molecule. This suggests that the factor probably acts as a primer in the polymerization of ATP molecules, being involved in the recognition between the mitochondrial poly(A) polymerase and the homologous RNA molecules which have to be polyadenylated.