背景资料：Vacuolar sorting proteins (VPSs) are required for trafficking normal endocytic and biosynthetic proteins to the vacuole and also play an important role in the budding process of cells. The ESCRT-II (endosomal sorting complex required for transport II) complex, which is involved in endocytosis of ubiquinated membrane proteins, is formed by Eap45, EAP30, and VPS25. These vacuolar sorting proteins are also involved in a multiprotein complex with RNA ploymerase II elongation factor (ELL). Eap45 (ELL-associated protein of 45 kDa), also known as vacuolar protein-sorting-associated protein 36, is a 386 amino acid protein containing a GLUE (GRAM-like ubiquitin-binding in Eap45) domain that mediates the binding to ubiquitin and phophoinosides. Since Eap45 colocalizes with ubiquinated proteins on late endosomes, it is likely that Eap45 plays a role in the endosomal sorting of ubiquniated cargo. There are two isoforms of Eap45 that exist as a result of alternative splicing events.