Induction of protein translation by ADAR1 within living cell nuclei is not dependent on RNA editing

Translation of mRNA is usually cytoplasmic. We report that the RNA editing enzyme ADAR1, which catalyzes the deamination of adenosine to inosine in double-stranded RNA substrates, induces translation within the nucleus, possibly at the surface of the nucleolus. This activity does not depend on RNA editing. Two regions within ADAR1 are defined that act independently of each other to induce translation: the first includes the double-stranded RNA binding domains (DRBMs) of ADAR1 while the second maps to the C-terminal portion of the catalytic domain. Point mutations within each domain are identified that reduce nuclear translation; those in the DRBM region are also known to diminish RNA binding. This report adds to the growing functionality ascribed to the nucleus.