Abstract
Ubiquitin and ubiquitin‐like proteins are known to be covalently conjugated to a variety of cellular substrates via a three‐step enzymatic pathway. These modifications lead to the degradation of substrates or change its functional status. The ubiquitin‐activating enzyme (E1) plays a key role in the first step of ubiquitination pathway to activate ubiquitin or ubiquitin‐like proteins. Ubiquitin‐activating enzyme E1‐domain containing 1 (UBE1DC1) had been proved to activate an ubiquitin‐like protein, ubiquitin‐fold modifier 1 (Ufm1), by forming a high‐energy thioester bond. In this report, UBE1DC1 is proved to activate another ubiquitin‐like protein, SUMO2, besides Ufm1, both in vitro and in vivo by immunological analysis. It indicated that UBE1DC1 could activate two different ubiquitin‐like proteins, SUMO2 and Ufm1, which have no significant similarity with each other. Subcellular localization in AD293 cells revealed that UBE1DC1 was especially distributed in the cytoplasm; whereas UBE1DC1 was mainly distributed in the nucleus when was cotransfected with SUMO2. It presumed that UBE1DC1 greatly activated SUMO2 in the nucleus or transferred activated‐SUMO2 to nucleus after it conjugated SUMO2 in the cytoplasm. J. Cell. Biochem. 104: 2324–2334, 2008. © 2008 Wiley‐Liss, Inc.