TORC1-dependent sumoylation of Rpc82 promotes RNA polymerase III assembly and activity

How organisms maintain homeostasis when confronted with environmental stress is an important question in biology. The master nutrient response regulator target of rapamycin complex 1 (TORC1) regulates many progrowth cellular processes, including transcription of genes required for protein synthesis. RNA polymerase III (RNAPIII) plays a crucial role in regulation of protein synthesis by transcribing tRNA genes. RNAPIII activity is known to be dependent on TORC1, but the underlying molecular mechanisms remain to be fully elucidated. Here, we show that TORC1 promotes sumoylation of a specific set of proteins mainly involved in transcription. Subunits of RNAPIII, particularly Rpc82, are among the most prominent TORC1-dependent SUMO substrates. Mechanistically, we demonstrate that TORC1-dependent sumoylation of Rpc82 is required for efficient assembly and full activity of the RNAPIII holoenzyme.