E2 ubiquitin-conjugating enzymes regulate the deubiquitinating activity of OTUB1

Abstract

OTUB1 is a Lys48-specific deubiquitinating enzyme that forms a complex in vivo with E2 ubiquitin conjugating enzymes including UBC13 and UBCH5. OTUB1 binds to E2~Ub thioester intermediates and prevent ubiquitin transfer, thereby non-catalytically inhibiting accumulation of polyubiquitin. We report here that a second role of OTUB1-E2 interactions is to stimulate OTUB1 cleavage of Lys48 polyubiquitin, and that this stimulation is regulated by the ratio of charged to uncharged E2 and by the concentration of Lys48-linked polyubiquitin and free ubiquitin. Structural and biochemical studies of human and worm OTUB1 and UBCH5B show that the E2 stimulates binding of the Lys48 polyubiquitin substrate by stabilizing folding of the OTUB1 N-terminal ubiquitin-binding helix. Our results suggest that OTUB1-E2 complexes in the cell are poised to regulate polyubiquitin chain elongation or degradation in response to changing levels of E2 charging and available free ubiquitin.

Select E2 enzymes differentially regulate parkin activation and mitophagy

“…Although E2s were believed to be ubiquitin-charged at steady-state (Jin et al, 2007), surprising differences in the ratio of charged and uncharged E2 enzymes (UBE2D2 versus UBE2N) in particular cells have recently been suggested (Wiener et al, 2013). Moreover, cellular stress increases ubiquitin charging of some E2s (Takada et al, 2001), whereas others are redox-regulated (Jahngen-Hodge et al, 1997) or sensitive to oxidative stress (Doris et al, 2012).…”

Casein kinase 2 (CK2) phosphorylates the deubiquitylase OTUB1 at Ser 16 to trigger its nuclear localization

“…Therefore, it is likely that their activity, target recognition as well as subcellular localization are tightly regulated. OTUB1 protein is detected ubiquitously in tissues and recent reports have shed light into the molecular functions of OTUB1 in deubiquitylating K48-linked ubiquitin chains as well as inhibiting the action of E2 ubiquitin-conjugating enzymes (1,(3)(4)(5)(6)(7)(8)(9)(10). OTUB1 has been reported to target many proteins for deubiquitylation, including TNF receptor-associated factors 3/6 (TRAF3/6) (11), estrogen receptor α (ERα) (12), the tumor suppressor protein p53 (13), and the cellular inhibitor of apoptosis c-IAP1 (14).…”

PTEN regulates RPA1 and protects DNA replication forks

“…Five DUB families have been identified including ovarian tumor proteases (OTUs) [15]. OTUB1 is an OTU family DUB cysteine protease highly specific for cleaving Lys48-linked polyubiquitin chains, which targets proteins for proteasomal degradation [16][17][18][19].…”