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STUB1, is a cytoplasmic protein whose amino acid sequence is highly preserved across species. STUB1 interacts with the molecular chaperones Hsc70-Hsp70 and Hsp90 through its TPR domain, whereas its U-box domain contains its E3 ubiquitin ligase activity. STUB1 interaction with these molecular chaperones lead to in client substrate ubiquitylation and degradation by the proteasome. therefore, STUB1 acts to tilt the folding-refolding mechanism towards the degradative pathway, and it serves as a link between the two. STUB1 inhibits anchorage-independent cell growth and metastatic potential by degrading oncogenic proteins including SRC-3. Inhibition of tyrosine kinase activity of Her-2/neu by quercetin specifies an lateration in the Her-2/neu structure which promotes STUB1 recruitments and down-regulation of Her-2/neu. STUB1 recognizes and mediates degradation of toxic, oligomeric forms of alphaSyn.

YOD1 is a Hydrolase which removes conjugated ubiquitin from proteins and takes part in endoplasmic reticulum-associated degradation (ERAD) for misfolded lumenal proteins. YOD1 is a highly conserved deubiquitinating enzyme belonging to the ovarian tumor (otubain) family, whose function has yet to be determined in mammalian cells. YOD1 is a component of a multiprotein complex with p97 as its nucleus, proposing a functional link to a pathway responsible for the dislocation of misfolded proteins from the endoplasmic reticulum. YOD1 variant xpression deprived of its deubiquitinating activity compels a halt on the dislocation reaction, as concluded by the stabilization of various dislocation substrates.

CDC34 takes part in the control of cell cycle and DNA replication. Cdc34 in association with different E3 complexes, including SCF, targets many different substrates for ubiquitination and degradation during cell division, signal transduction, and development. Cdc34 substrates that have been characterized include B-Myb, Wee1, MyoD, ATF5, p27Xic1, and p27Kip1. Additionally, substrates such as p21Cip1, E2F, cyclin E, and cyclin D are putative substrates of Cdc34 by virtue of their SCF requirement for proteolysis. Cdc34 is self-associate through a domain in the C-terminus, and is phosphorylated and ubiquitinylated in vivo. CDC34is useful for in vitro ubiquitinylation reactions.

CDC34 is important in the control of cell cycle and DNA replication. Cdc34 in association with different E3 complexes, including SCF, has been shown to target many different substrates for ubiquitination and degradation during cell division, signal transduction, and development. Cdc34 substrates that have been characterized include I?B, B-Myb, Wee1, MyoD, ICERII?, ATF5, p27Xic1, and p27Kip1. Additionally, substrates such as ?-catenin, p21Cip1, E2F, cyclin E, and cyclin D are putative substrates of Cdc34 by virtue of their SCF requirement for proteolysis. Cdc34 has been demonstrated to self-associate through a domain in the C-terminus, and is phosphorylated and ubiquitinylated in vivo. This protein is useful for in vitro ubiquitinylation reactions.

HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 5 (HERC5) is a member of the HERC family of ubiquitin ligases, found in a cluster of HERC family genes on chromosome 4. HERC5 is a protein with a HECT domain and 5 RCC1 repeats. The HERC5 protein localizes to the cytoplasm and perinuclear region and serves as an INF-induced E3 protein ligase that mediates ISGylation of protein targets. HERC5 exhibits antiviral activity towards HIV-1, influenza A virus and human papillomavirus. HERC5 is a major E3 ligase for ISG15 conjugation. HERC5 also serves as a positive regulator of innate antiviral response in cells induced by INF. Pro-inflammatory cytokines upregulate HERC5 in endothelial cells. HERC5 is physically connected with polyribosomes, broadly modifies recently synthesized proteins in a cotranslational fashion.

SAE1 and SAE2 form heterodimers which take part in the posttranslational modification of proteins (sumoylation). This process regulates protein structure as well as intracellular localization of the target. SAE1/SAE2 may indicate on dermatomyositis (DM) as autoantibodies against those 2 proteins have been found in patients.

UCHL1 (PGP9.5) belongs to a gene family whose products hydrolyze small C-terminal adducts of ubiquitin to produce the ubiquitin monomer. Protein Gene Product (PGP9.5) is a neuron specific protein, structurally and immunologically distinct from neuron specific enolase. Human UCHL1 and UCHL3 have an extremely complicated knot structure for a protein, with five knot crossings. It is considered that the knot structure may increase a protein's resistance to degradation in the proteasome.
The protein, which has a molecular weight of 27 kDa was first defined by high resolution two dimetional PAGE. Standard immunohistochemical techniques have demonstrated the presence of PGP9.5 in neurons and nerve fibers at all levels of the central and peripheral nervous system, in many neurodcrine cells, in segments of the renal tubules, in spermatogonia and leydig cells of the testis, in ova and in some cells of both the pregnant and non pregnant corpus luteum. A point mutation (I93M) in UCHL1 is implicated as the cause of Parkinson's disease in one kindred. On the other hand, a polymorphism (S18Y) in UCHL1 has been found to be associated with a reduced risk for Parkinson's disease. Furthermore, UCHL1 is associated with the Alzheimer's disease, and required for normal synaptic and cognitive function.

MAP1LC3B is a member of the MAP1 LC3 family. MAP1LC3B is a subunit of neuronal microtubule-associated MAP1A and MAP1B proteins, that are involved in microtubule assembly and important for neurogenesis. In addition, MAP1LC3B takes part in formation of autophagosomal vacuoles and is expressed mainly in heart, testis, brain and skeletal muscle.

Ubiquitin Carboxyl-Terminal Esterase L1 (UCHL1) is a part of a family whose products hydrolyze small C-terminal adducts of ubiquitin to create the ubiquitin monomer. UCHL1 is a part of the ubiquitin system, which regulates many biological activities. UCHL1 is a thiol protease that distinguishes and hydrolyzes a peptide bond at the C-terminal glycine of ubiquitin. UCHL1 binds to free monoubiquitin and avoids its degradation in lysosomes.

Tripartite Motif Containing 33 (TRIM33) belongs to the tripartite motif family. This motif includes 3 zinc-binding domains, a RING, a B-box type 1 and a B-box type 2, and a coiled-coil region. TRIM33 is assumed to be a transcriptional corepressor. TRIM33 functions as an E3 ubiquitin-protein ligase. TRIM33 also promotes SMAD4 ubiquitination, nuclear exclusion and degradation via the ubiquitin proteasome pathway. In addition, TRIM33 inhibits the transcriptional response to TGF-beta/BMP signaling cascade. Furthermore, TRIM33 has a role in the control of cell proliferation.

MAP1LC3B is a member of the MAP1 LC3 family. MAP1LC3B is a subunit of neuronal microtubule-associated MAP1A and MAP1B proteins, that are involved in microtubule assembly and important for neurogenesis. In addition, MAP1LC3B takes part in formation of autophagosomal vacuoles and is expressed mainly in heart, testis, brain and skeletal muscle.

SAE1 is part of the ubiquitin-activating E1 family of proteins and participates in the significant first step of the UBL1 conjugation pathway. Proteins conjugated to Ub are marked for progressive degradation by the 26S Proteasome. SAE1 acts as a UBLI E1 ligase mediating the ATP-dependent activation of UBL1. SAE1 binds with UBLE1A and UBLE1B to form a heterodimer which can bind UBL1. SAE1 is a dimeric enzyme that takes part as a E1 ligase for SUMO1, SUMO2, SUMO3, and probably SUMO4. SAE1 regulates ATP-dependent activation of SUMO proteins and formation of a thioester with a conserved cysteine residue on SAE2.

Autophagy Related 3 (ATG3) is a conjugating enzyme essential for the cytoplasm to vacuole transport (Cvt), autophagy, and mitochondrial homeostasis. ATG3 is localizes to the cytoplasm and is expressed in tissues with predominant levels found in kidney, placenta, liver, heart and skeletal muscle. ATG3 catalyzes a reaction which is necessary for autophagy. That reaction is the formation of the Atg8-phosphatidylethanolamine (ATG-PE) conjugate.

Ubiquitin-like-conjugating enzyme ATG10 (ATG10) is a 220 amino acid protein which localizes to the cytoplasm and has a role in autophagy, specifically acting as an E2-like enzyme providing Atg recognition sites during autophagosome synthesis. ATG10 functions as an E2-like enzyme which catalyzes the conjugation of ATG12 to ATG5, which is required for autophagy. In addition, ATG10 interacts with ATG12 in human embryonic kidney cells in the presence of ATG7. ATG10 probably serves as an ATG5-recognition molecule. Furthermore, ATG10 has a role in adenovirus-mediated cell lysis.

Autophagy Related 3 (ATG3) is a conjugating enzyme essential for the cytoplasm to vacuole transport (Cvt), autophagy, and mitochondrial homeostasis. ATG3 is localizes to the cytoplasm and is expressed in tissues with predominant levels found in kidney, placenta, liver, heart and skeletal muscle. ATG3 catalyzes a reaction which is necessary for autophagy. That reaction is the formation of the Atg8-phosphatidylethanolamine (ATG-PE) conjugate.

Protein Tyrosine Phosphatase Receptor Type N (PTPRN) is a catalytically inactive protein and a major target of autoimmune response in diabetes mellitus. The long C-terminal intracellular tail covers the majority of autoantibody epitopes. PTPRN is expressed in neural, neuroendocrine and pancreatic islet cells.

Ring Finger & CHY Zinc Finger Domain Containing 1 (RCHY1) acts as an ubiquitin ligase. RCHY1 mediates E3-dependent ubiquitination and proteasomal degradation of target proteins which among them are TP53, HDAC1 and CDKN1B, consequently regulating their levels and cell cycle progression. RCHY1 is also increases AR transcription factor activity.

STAM Binding Protein (STAMBP) is a zinc metalloprotease which specifically cleaves Lys-63-linked polyubiquitin chains, however it doesn’t cleave Lys-48-linked polyubiquitin chains. STAMBP has a role in signal transduction for cell growth and MYC induction mediated by IL-2 and GM-CSF. In addition, STAMBP potentiates BMP signaling by antagonizing the inhibitory action of SMAD6 and SMAD7. STAMBP also has a major role in regulation of cell surface receptor-mediated endocytosis and ubiquitin-dependent sorting of receptors to lysosomes. Endosomal localization of STAMBP is essential for efficient EGFR degradation but not for its internalization. STAMBP is also involved in the negative regulation of PI3K-AKT-mTOR and RAS-MAP signaling pathways.

PARK2 is an element in a multiprotein E3 ubiquitin ligase complex which mediates the targeting of substrate proteins for proteasomal degradation. PARK2 alterations can result in Parkinson disease and autosomal recessive juvenile Parkinson disease. Alternative splicing creates multiple transcript variants encoding distinct isoforms.

UCK1 is a uridine-cytidine kinase which catalyzes the phosphorylation of uridine and cytidine to uridine monophosphate and cytidine monophosphate. UCK1 does not phosphorylate deoxyribonucleosides or purine ribonucleosides. UCK1 is also phosphorylates uridine and cytidine analogs and uses ATP and GTP as a phosphate donor.

E3 ubiquitin ligase RNF4 (RNF4) contains a RING finger motif and functions as a transcription regulator. RNF4 interacts with, and inhibits the activity of, TRPS1, a transcription suppressor of GATA-mediated transcription. Transcription repressor ZNF278/PATZ also interacts with the RNF4 protein thus reducing the enhancement of androgen receptor-dependent transcription mediated by RNF4. RNF4 is broadly expressed at low levels in many tissues and highly expressed in the testis.

Proteasomal ubiquitin receptor ADRM1 (ADRM1) functions as a proteasomal ubiquitin receptor. ADRM1 is an integral plasma membrane protein which promotes cell adhesion. ADRM1 is assumed to undergo O-linked glycosylation. ADRM1 employs the deubiquitinating enzyme UCHL5 at the 26S proteasome and promotes its activity.

Proteasomal ubiquitin receptor ADRM1 (ADRM1) functions as a proteasomal ubiquitin receptor. ADRM1 is an integral plasma membrane protein which promotes cell adhesion. ADRM1 is assumed to undergo O-linked glycosylation. ADRM1 gene expression is induced by gamma interferon in some cancer cells. ADRM1 employs the deubiquitinating enzyme UCHL5 at the 26S proteasome and promotes its activity.

Ring Finger Protein 34 (RNF34) has E3 ubiquitin-protein ligase activity. RNF34 has a RINF finger, a motif recognized to be involved in protein-protein and protein-DNA interactions. RNF34 regulates the levels of CASP8 and CASP10 by targeting them for proteasomal degradation. In addition, RNF34 protects cells against apoptosis induced by TNF. RNF34 also binds phosphatidylinositol 5-phosphateand phosphatidylinositol 3-phosphate. Alternatively splicing results in multiple transcript variants encoding distinct isoforms.