A ubiquitin-binding motif required for intramolecular monoubiquitylation, the CUE domain

Abstract

Monoubiquitylation is a regulatory signal, like phosphorylation, that can alter the activity, location or structure of a protein. Monoubiquitin signals are likely to be recognized by ubiquitin-binding proteins that transmit the regulatory information conferred by monoubiquitylation. To identify monoubiquitin-binding proteins, we used a mutant ubiquitin that lacks the primary site of polyubiquitin chain formation as bait in a two-hybrid screen. The C-terminus of Vps9, a protein required in the yeast endocytic pathway, interacted speci®cally with monoubiquitin. The region required for monoubiquitin binding mapped to the Vps9 CUE domain, a sequence previously identi®ed by database searches as similar to parts of the yeast Cue1 and mammalian Tollip proteins. We demonstrate that CUE domains bind directly to monoubiquitin and we have de®ned crucial interaction surfaces on both binding partners. The Vps9 CUE domain is required to promote monoubiquitylation of Vps9 by the Rsp5 hect domain ubiquitin ligase. Thus, we conclude that the CUE motif is an evolutionarily conserved monoubiquitin-binding domain that mediates intramolecular monoubiquitylation.

Cbl-b interacts with ubiquitinated proteins; differential functions of the UBA domains of c-Cbl and Cbl-b

“…Interestingly, this L to A mutation abolishes the interaction of the UBA domain of Ddi1 with ubiquitin (Bertolaet et al, 2001b), implying a difference in the interaction with ubiquitin. This suggests that these domains vary in their interaction with ubiquitin, as is the case for the two HsRad23a UBA domains (Mueller et al, 2004), the p47 UBA domain (Yuan et al, 2004) and the related CUE domain (Kang et al, 2003;Shih et al, 2003). The determination of the structure of the UBA b and the UBA c should allow for the differences in their affinity for ubiquitin to be elucidated.…”

“…The UIM and CUE domains of a number of proteins also have been shown to mediate their monoubiquitination (reviewed in Schnell and Hicke, 2003). For example, the yeast E3 ligase, Rsp5, binds the CUE domain of Vsp9 and ubiquitinates it Shih et al, 2003). Interestingly, the UBA domain of the yeast protein, Gts1p, is involved in its ubiquitination and degradation (Saito et al, 2002), suggesting that, like other ubiquitin binding domains, the UBA domain may mediate intermolecular ubiquitination.…”

Ubiquitination of mRNA cycling sequence binding protein from Leishmania donovani (LdCSBP) modulates the RNA endonuclease activity of its Smr domain

“…Since the presence of CUE domain in a protein was shown to promote its intramolecular ubiquitination [15], the possibility of ubiquitination of LdCSBP was explored. An in vitro reaction was carried out with the S-100 extract from L. donovani promastigotes supplemented with ubiquitin and an energy regeneration system.…”

Role of protein ubiquitylation in regulating endocytosis of receptor tyrosine kinases

“…Rabex and its yeast homolog Vps9 are guanine nucleotide exchange factors that promote endosomal membrane fusion through activation of the Rab5/Vps21 GTPase (Esters et al, 2001). Rabex/Vps9 contains a CUE (coupling of ubiquitin conjugation to endoplasmic reticulum degradation) domain that, like the UIM, binds ubiquitin and directs self-monoubiquitylation (Donaldson et al, 2003;Shih et al, 2003). Consistent with the possibility that CUE domains and UIM motifs share functional characteristics, the interaction between the CUE domain and ubiquitin appears to mediate recognition of ubiquitylated cargo, as well as activate Rabex/Vps9 upon cargo binding.…”