OTUB1
Domain
In addition to ubiquitin-binding at the Cys-91 active site, a proximal ubiquitin-binding site is also present at Cys-23 Occupancy of the active site is needed to enable tight binding to the second site. Distinct binding sites for the ubiquitins may allow to discriminate among different isopeptide linkages (i.e. 'Lys-48'-, 'Lys-63'-linked polyubiquitin) in polyubiquitin substrates and achieve linkage-specific deubiquitination.
Function
Hydrolase that can specifically remove 'Lys-48'-linked conjugated ubiquitin from proteins and plays an important regulatory role at the level of protein turnover by preventing degradation (PubMed:12401499, PubMed:12704427, PubMed:14661020, PubMed:23827681). Regulator of T-cell anergy, a phenomenon that occurs when T-cells are rendered unresponsive to antigen rechallenge and no longer respond to their cognate antigen (PubMed:14661020). Acts via its interaction with RNF128/GRAIL, a crucial inductor of CD4 T-cell anergy (PubMed:14661020). Isoform 1 destabilizes RNF128, leading to prevent anergy (PubMed:14661020). In contrast, isoform 2 stabilizes RNF128 and promotes anergy (PubMed:14661020). Surprisingly, it regulates RNF128-mediated ubiquitination, but does not deubiquitinate polyubiquitinated RNF128 (PubMed:14661020). Deubiquitinates estrogen receptor alpha (ESR1) (PubMed:19383985). Mediates deubiquitination of 'Lys-48'-linked polyubiquitin chains, but not 'Lys-63'-linked polyubiquitin chains (PubMed:18954305, PubMed:19211026, PubMed:23827681). Not able to cleave di-ubiquitin (PubMed:18954305, PubMed:23827681). Also capable of removing NEDD8 from NEDD8 conjugates, but with a much lower preference compared to 'Lys-48'-linked ubiquitin (PubMed:18954305, PubMed:23827681).
Plays a key non-catalytic role in DNA repair regulation by inhibiting activity of RNF168, an E3 ubiquitin-protein ligase that promotes accumulation of 'Lys-63'-linked histone H2A and H2AX at DNA damage sites (PubMed:20725033, PubMed:22325355). Inhibits RNF168 independently of ubiquitin thioesterase activity by binding and inhibiting UBE2N/UBC13, the E2 partner of RNF168, thereby limiting spreading of 'Lys-63'-linked histone H2A and H2AX marks (PubMed:20725033, PubMed:22325355). Inhibition occurs by binding to free ubiquitin: free ubiquitin acts as an allosteric regulator that increases affinity for UBE2N/UBC13 and disrupts interaction with UBE2V1 (PubMed:20725033, PubMed:22325355). The OTUB1-UBE2N/UBC13-free ubiquitin complex adopts a configuration that mimics a cleaved 'Lys48'-linked di-ubiquitin chain (PubMed:20725033, PubMed:22325355). Acts as a regulator of mTORC1 and mTORC2 complexes (PubMed:29382726, PubMed:35927303). When phosphorylated at Tyr-26, acts as an activator of the mTORC1 complex by mediating deubiquitination of RPTOR via a non-catalytic process: acts by binding and inhibiting the activity of the ubiquitin-conjugating enzyme E2 (UBE2D1/UBCH5A, UBE2W/UBC16 and UBE2N/UBC13), thereby preventing ubiquitination of RPTOR (PubMed:35927303). Can also act as an inhibitor of the mTORC1 and mTORC2 complexes in response to amino acids by mediating non-catalytic deubiquitination of DEPTOR (PubMed:29382726).
Post-translational modifications
Phosphorylation at Tyr-26 by SRC and SRMS promotes deubiquitination of RPTOR via a non-catalytic process.
Sequence Similarities
Belongs to the peptidase C65 family.
Tissue Specificity
Isoform 1 is ubiquitous. Isoform 2 is expressed only in lymphoid tissues such as tonsils, lymph nodes and spleen, as well as peripheral blood mononuclear cells.
Cellular localization
- Cytoplasm
Alternative names
OTB1, OTU1, HSPC263, OTUB1, Ubiquitin thioesterase OTUB1, Deubiquitinating enzyme OTUB1, OTU domain-containing ubiquitin aldehyde-binding protein 1, Otubain-1, Ubiquitin-specific-processing protease OTUB1, hOTU1