Background: TOM1 (target of myb1) was originally identified as a gene activated by the expression of oncogenic Myb1. TOM1 has been shown to form a complex with tollip (toll-interacting protein) and to bind ubiquitin chains. It has also been shown to bind to clathrin heavy chain and is proposed to function to link polyubiquitinated proteins to clathrin and regulate endosomal trafficking of ubiquitinated proteins. Recent evidence shows that TOM1 bridges endofin to clathrin and is critical for the endosomal targeting of clathrin by endofin.