Alternative titles; symbols
HGNC Approved Gene Symbol: UBE2J1
Cytogenetic location: 6q15 Genomic coordinates (GRCh38) : 6:89,326,625-89,352,722 (from NCBI)
UBE2J1 is an E2 ubiquitin-conjugating enzyme involved in the endoplasmic reticulum (ER) quality control machinery for proteasomal degradation. UBE2J1 is important in late spermatogenesis and male fertility (Koenig et al., 2014).
Lester et al. (2000) cloned chick Ube2j1, which they termed Ncube1, and identified orthologs in various species, including human NCUBE1 and NCUBE2 (UBE2J2; 619756). The human NCUBE1 protein contains 318 amino acids and shares 72% and 91% amino acid identity with chick and mouse Ncube1. All NCUBE proteins have a conserved N-terminal domain containing the active site and a C-terminal extension containing a transmembrane domain. All vertebrate NCUBE1 proteins also have a nuclear localization signal. RT-PCR analysis showed that chick Ncube1 was expressed in all tissues examined, with highest levels in liver, brain, and spleen.
Oh et al. (2006) determined that human UBC6 (UBE2J2) and UBC6E share 64% and 46% amino acid identity, respectively, with yeast Ubc6 in their catalytic cores and are invariant at their catalytic cysteines. Both human proteins are tail-anchored proteins with hydrophobic C-terminal transmembrane domains. UBC6 and UBC6E are conserved in all eukaryotic kingdoms, including fungi, protists, plant, and metazoa, with UBC6E subfamily members exhibiting divergent and longer C-terminal segments.
Gross (2015) mapped the UBE2J1 gene to chromosome 6q15 based on an alignment of the UBE2J1 sequence (GenBank AF161502) with the genomic sequence (GRCh38).
Cystic fibrosis (219700) arises from misfolding and premature degradation of CFTR (602421) containing a deletion of phe508 (delF508; 602421.0001). Younger et al. (2006) identified an ER membrane-associated ubiquitin ligase complex containing the E3 RMA1 (RNF5; 602677), the E2 UBC6E (UBE2J1), and derlin-1 (DERL1; 608813) that cooperated with the cytosolic HSC70 (HSPA8; 600816)/CHIP (STUB1; 607207) E3 complex to triage CFTR and delFl508. Derlin-1 retained CFTR in the ER membrane and interacted with RMA1 and UBC6E to promote proteasomal degradation of CFTR. RMA1 could recognize folding defects in delF508 coincident with translation, whereas CHIP appeared to act posttranslationally. A folding defect in delF508 detected by RMA1 involved the inability of the second membrane-spanning domain of CFTR to productively interact with N-terminal domains. Younger et al. (2006) concluded that the RMA1 and CHIP E3 ubiquitin ligases act sequentially in ER membrane and cytosol to monitor the folding status of CFTR and delF508.
Using purified recombinant proteins, Oh et al. (2006) demonstrated that human UBC6 and UBC6E were E2 enzymes capable of accepting ubiquitin from E1 in an ATP-dependent manner by their catalytic cysteines. Both enzymes were upregulated by the unfolded protein response (UPR) in Panc-1 human secretory cells, with UBC6E expression increasing slowly in response to UPR, and UBC6 expression increasing rapidly and then dissipating. Analysis with transfected HEK293 cells, as well as endogenous UBC6E in Panc-1 cells, showed that UBC6E was phosphorylated in response to ER stress at ser184, a residue located within a highly charged segment between the catalytic core and the transmembrane domain. Analysis with mouse embryonic fibroblasts revealed that ER stress-induced phosphorylation of Ubc6e required Perk (EIF2AK3; 604032), an ER transmembrane serine/threonine protein kinase. However, phosphorylation had no direct role in determining ER localization of UBC6E, as phosphorylated UBC6E was stable and remained localized to the ER membrane. Furthermore, UBC6E phosphorylation did not affect interaction of UBC6E with its E3 partner or ER-associated degradation (ERAD) of its substrate. Instead, phosphorylation appeared to alter the enzymatic activity of UBC6E, as formation of ubiquitin-UBC6E thiol-ester bond was reduced for phosphorylated UBC6E.
Using human cell lines, Mueller et al. (2008) identified several components of a protein complex required for retrotranslocation or dislocation of misfolded proteins from the ER lumen to the cytosol for proteasome-dependent degradation. These included SEL1L (602329), HRD1 (SYVN1; 608046), derlin-2 (DERL2; 610304), the ATPase p97 (VCP; 601023), PDI (P4HB; 176790), BIP (HSPA5; 138120), calnexin, AUP1 (602434), UBXD8 (FAF2), UBC6E, and OS9 (609677).
Burr et al. (2011) presented evidence that human UBE2J1 and the E3 ligase HRD1 were required for ubiquitination and degradation of misfolded major histocompatibility complex class I heavy chains.
Using phosphoproteomics, Menon et al. (2013) identified mouse and human UBE2J1 as a potential substrate of MK2 (MAPKAPK2; 602006). Under cytosolic stress conditions, mouse Ube2j1 was phosphorylated at ser184, which also occurs under ER stress. Phosphorylation under cytosolic stress, but not ER stress, was sensitive to MK2, MK5 (MAPKAP5; 606723), and p38 (MAPK14; 600289) inhibitors and was abrogated in Mk2 and Mk3 (MAPKAPK3; 602130) double-knockout mouse cells, but not in Mk5-knockout mouse cells. Pull-down analysis in transfected human embryonic kidney cells demonstrated interaction of MK2 and mouse Ube2j1. MK2 phosphorylated recombinant mouse Ube2j1, but not a ser184-to-ala Ube2j1 mutant, in an in vitro kinase assay. However, the mutant protein could ubiquitinate the ER-synthesized TCRA (see TRAC; 186880) substrate, similar to wildtype Ube2j1. Ube2j1 was also phosphorylated in response to lipopolysaccharide stimulation of macrophages and contributed to Tnf (191160) biosynthesis. Treatment of mouse macrophages with small interfering RNA to Ube2J1 blocked Tnf secretion. Menon et al. (2013) concluded that UBE2J1 is involved in MK2-dependent translational control of TNF synthesis.
Koenig et al. (2014) found that Ube2j1 -/- mice were viable at birth, but about half died at the time of weaning. There was no differential mortality after weaning. Surviving Ube2j1 -/- mice were smaller and weighed less than wildtype mice, in spite of comparable feeding. Ube2j1 +/- mice had intermediate body weights. In the absence of Ube2j1, specific ER quality machinery proteins accumulated, probably due to posttranslational stabilization. Embryonic fibroblasts from Ube2j1-/- mice were more susceptible to SV40 virus infection, but not to ER stress. Ube2j1-/- B cells matured and secreted immunoglobulin normally. Female and male mice lacking Ube2j1 were sexually active, but the males were infertile and had reduced epididymal sperm with severely impaired motility due to defects in flagella function and aberrant morphology. Spermatid development was also defective in Ube2j1 -/- mice. Koenig et al. (2014) concluded that UBE2J1 is essential for spermiogenesis.
Burr, M. L., Cano, F., Svobodova, S., Boyle, L. H., Boname, J. M., Lehner, P. J. HRD1 and UBE2J1 target misfolded MHC class I heavy chains for endoplasmic reticulum-associated degradation. Proc. Nat. Acad. Sci. 108: 2034-2039, 2011. [PubMed: 21245296] [Full Text: https://doi.org/10.1073/pnas.1016229108]
Gross, M. B. Personal Communication. Baltimore, Md. 1/22/2015.
Koenig, P.-A., Nicholls, P. K., Schmidt, F. I., Hagiwara, M., Maruyama, T., Frydman, G. H., Watson, N., Page, D. C., Ploegh, H. L. The E2 ubiquitin-conjugating enzyme UBE2J1 is required for spermiogenesis in mice. J. Biol. Chem. 289: 34490-34502, 2014. [PubMed: 25320092] [Full Text: https://doi.org/10.1074/jbc.M114.604132]
Lester, D., Farquharson, C., Russell, G., Houston, B. Identification of a family of noncanonical ubiquitin-conjugating enzymes structurally related to yeast UCB6. Biochem. Biophys. Res. Commun. 269: 474-480, 2000. [PubMed: 10708578] [Full Text: https://doi.org/10.1006/bbrc.2000.2302]
Menon, M. B., Tiedje, C., Lafera, J., Ronkina, N., Konen, T., Kotlyarov, A., Gaestel, M. Endoplasmic reticulum-associated ubiquitin-conjugating enzyme Ube2j1 is a novel substrate of MK2 (MAPKAP kinase-2) involved in MK2-mediated TNF-alpha production. Biochem. J. 456: 163-172, 2013. Note: Erratum: Biochem. J. 457: 229 only, 2014. [PubMed: 24020373] [Full Text: https://doi.org/10.1042/BJ20130755]
Mueller, B., Klemm, E. J., Spooner, E., Claessen, J. H., Ploegh, H. L. SEL1L nucleates a protein complex required for dislocation of misfolded glycoproteins. Proc. Nat. Acad. Sci. 105: 12325-12330, 2008. [PubMed: 18711132] [Full Text: https://doi.org/10.1073/pnas.0805371105]
Oh, R. S., Bai, X., Rommens, J. M. Human homologs of Ubc6p ubiquitin-conjugating enzyme and phosphorylation of HsUbc6e in response to endoplasmic reticulum stress. J. Biol. Chem. 281: 21480-21490, 2006. [PubMed: 16720581] [Full Text: https://doi.org/10.1074/jbc.M601843200]
Younger, J. M., Chen, L., Ren, H.-Y., Rosser, M. F. N., Turnbull, E. L., Fan, C.-Y., Patterson, C., Cyr, D. M. Sequential quality-control checkpoints triage misfolded cystic fibrosis transmembrane conductance regulator. Cell 126: 571-582, 2006. [PubMed: 16901789] [Full Text: https://doi.org/10.1016/j.cell.2006.06.041]