Abstract
MPN+ domain proteins play a pivotal role in the demodification of ubiquitin and ubiquitin-like proteins. Among the three identified MPN+ domain proteins, RPN11 (deubiquitylation, 26S proteasome subunit) and CSN5 (deneddylation, COP9 signalosome subunit) are well characterized. AMSH, the third and obviously the last member of the MPN+ family, still remains to be characterized. In mammals, AMSH was reported to have deubiquitylating activity towards K63-linked ubiquitin chains, and therefore thought to be involved in the regulation of endocytosis.
In our study, we aim to elucidate the functional mechanism of the 3 AMSH proteins in Arabidopsis thaliana, taking advantage of available mutant lines. We found that all three AMSH proteins possess MPN+ domain dependent deubiquitylating activity in vitro, and AMSH3 was found to be essential for plant growth. Together with localization and biochemical studies, we would like to discuss the function of AMSH in higher plants.
