Proteins (IMAGE) UT Southwestern Medical Center Caption Han, Mendell, and colleagues discovered an assembly of proteins that form a ubiquitin ligase (yellow) that targets microRNAs (red) and their associated Argonaute proteins (blue) for degradation. This mechanism broadly regulates microRNA levels in multiple cell types and tissues. Credit UT Southwestern Medical Center Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.