sentences:  Poly-ubiquitin chains tag proteins for degradation by the proteasome, which causes hydrolysis of tagged proteins into smaller peptides.Tankyrase (TNKS), an ADP-ribosyltransferase, interacts with proteasome regulator PI31.Evidence in "Drosophila" and human cell lines demonstrates that the Ankyrin domain (ANK) of TNKS facilitates interaction with the N-terminal TNKS-binding motif and C-terminal HbYX domain of PI31.