Mapping ubiquitin modifications reveals new functions for the yeast nuclear pore complex.

Covalent attachment of ubiquitin to target proteins, or ubiquitylation, has emerged as one of the most prevalent posttranslational modifications (PTMs), regulating nearly every cellular pathway. The diversity of functions associated with this particular PTM stems from the myriad ways in which a target protein can be modified by ubiquitin, e.g., monoubiquitin, multi-monoubiquitin, and polyubiquitin linkages. In the current study, we took a systematic approach to analyze the ubiquitylation profiles of the yeast Saccharomyces cerevisiae nuclear pore complex (NPC) proteins or nucleoporins. We found the yeast NPC to be extensively modified by ubiquitin with highly variable ubiquitylation profiles, suggesting that dissection of these modifications may provide new insights into the regulation of NPC functions and reveal additional roles for nucleoporins beyond nuclear transport.