Tumor Suppressor ARF Promotes Non-classic Proteasome-independent Polyubiquitination of COMMD1

Abstract

Although the tumor suppressor ARF is generally accepted for its essential role in activating the p53 pathway, its p53-independent function has also been proposed. Here, we report that ARF associates with COMMD1 and promotes Lys 63 -mediated polyubiquitination of COMMD1 in a p53-independent manner. We found that ARF interacts with COMMD1 in vivo. Deletion analysis of ARF suggested that the N-terminal amino acids 15-45 are important for its interaction with COMMD1. In addition, we found that endogenous ARF redistributes from the nucleolus to the nucleoplasm and interacts with COMMD1 when DNA is damaged by actinomycin D. Interestingly, we found that ARF promotes the polyubiquitination of COMMD1 through Lys 63 of ubiquitin but not the polyubiquitination of Lys 48 , which does not target COMMD1 for proteasome-dependent proteolysis. Moreover, ARF mutants lacking the domain interacting with COMMD1 did not promote COMMD1 polyubiquitination, indicating that physical association is a prerequisite condition for the polyubiquitination process. Together, these data suggest that the ability to promote Lys 63 -mediated polyubiquitination of COMMD1 is a novel property of ARF independent of p53.

COMMD1 Forms Oligomeric Complexes Targeted to the Endocytic Membranes via Specific Interactions with Phosphatidylinositol 4,5-Bisphosphate

“…Alternatively, the presence of COMMD1 in endosomes/MVB may influence the fate of ATP7B by shifting equilibrium from recycling to targeting to multivesicular bodies and lysosomal degradation. The potential role of COMMD1 in membrane protein recycling is supported by the recent observation of K63-linked ubiquitination of COMMD1 (34), which is a modification implicated in targeting the apical membrane proteins into the endosomal recycling pathway (35). The observation that immunofluorescence shows little COMMD1/ATP7B co-localization is consistent with other studies (9) and is likely to reflect a more general role of COMMD1 as a scaffold for various proteins (Fig.…”

Clusterin and COMMD1 Independently Regulate Degradation of the Mammalian Copper ATPases ATP7A and ATP7B

“…7, B and D, lane 6). This observation was consistent with a previous study that showed that COMMD1 was degraded via the proteasomal and not by the lysosomal pathway (54).…”

Cu,Zn Superoxide Dismutase Maturation and Activity Are Regulated by COMMD1

“…Consistent with the notion that COMMD1 functions in multiple cellular pathways, COMMD1 is ubiquitously expressed and located at different subcellular sites. COMMD1 has been detected in the nucleus (23,32) and in the cytoplasm (33), where it may be associated with intracellular membranes (29,33). In this study, we identified COMMD1 as a novel interaction partner of SOD1, and we show that COMMD1 plays an important role in the maturation of SOD1.…”