Demethylation of ribosomal RNA by hepatocyte microsomal preparations.

Previous work has shown that hypomethylation of rRNA is an important control for protein synthesis in rat hepatocytes, and that the net hypomethylation appears to arise from cytoplasmic events. Here we show that demethylation of rRNA is catalyzed by microsomal preparations. The rRNA demethylation is dependent upon NADPH and is almost completely inhibited by carbon monoxide. Demethylation appears to increase following galactosamine intoxication, a hepatotoxin which induces hypomethylation of rRNA and inhibition of protein synthesis.