Dynamic ubiquitination determines transcriptional activity of the plant immune coactivator NPR1 (eLIFE)

Dynamic ubiquitination determines transcriptional activity of the plant immune coactivator NPR1

Plants (and animals) need to strike a delicate balance when activating their immune responses: not too much and not too little. The transcriptional coactivator NPR1 [nonexpressor of pathogenesis-related (PR) genes 1] has long been known to have a key role in this balance, and it itself has a complex regulation that includes regulated nuclear import and high rates of protein turnover. Now, Skelly et al. have found that this ubiquitin-mediated proteolysis also involves a delicate balance. The authors found that addition of a small number of ubiquitin monomers by the CRL3 E3 ligase activates NPR1, whereas further ubiquitination by an E4 ligase leads to its proteolysis. The authors propose “the sequential actions of E3 and E4 ligases may generate a transcriptional timer that controls the activity and lifetime of unstable (co)activators.” (Summary by Mary Williams) eLIFE 10.7554/eLife.47005