The characterization of molecules recognized by patients with autoimmune diseases has provided significant insights into important biological pathways. In these studies, we define Ufd2 (a novel E4 polyubiquitylating enzyme) as a new autoantigen in scleroderma, and show that it regulates chromosome condensation and separation during mitosis in human cells. Ufd2 is regulated by phosphorylation in mitosis. Inhibition of Ufd2 expression results in mitotic arrest at the metaphase-anaphase transition, where cells manifest abnormal chromosome morphology, missegregated chromosomes, irregular spindles, and premature separation of sister chromatids. This is accompanied by premature separase activation, and accumulation of securin in a novel modified form. We further demonstrate that Ufd2 directly and efficiently ubiquitylates securin in vitro and is required for securin polyubiquitylation in vivo. This is the first description of a physiologic substrate for Ufd2, establishing this E4 enzyme as an important regulator of chromosome condensation and separation during mitosis in human cells. Its targeting in scleroderma, together with many other components of the mitotic machinery, reinforces the concept that mitotic cells may be an important focus of the autoimmune response in this disease.
SciCrunch is a data sharing and display platform. Anyone can create a custom portal where they can select searchable subsets of hundreds of data sources, brand their web pages and create their community. SciCrunch will push data updates automatically to all portals on a weekly basis. User communities can also add their own data to scicrunch, however this is not currently a free service.