Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P62988 (Ubiquitin)
 4,326 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The covalent attachment of ubiquitin to target proteins influences various cellular processes, including DNA repair, NF-kappaB signalling and cell survival. The most common mode of regulation by ubiquitin-conjugation involves specialized ubiquitin-binding proteins that bind to ubiquitylated proteins and link them to downstream biochemical processes. Unravelling how the ubiquitin-message is recognized is essential because aberrant ubiquitin-mediated signalling contributes to tumour formation. Recent evidence indicates that inhibitor of apoptosis (IAP) proteins are frequently overexpressed in cancer and their expression level is implicated in contributing to tumorigenesis, chemoresistance, disease progression and poor patient-survival. Here, we have identified an evolutionarily conserved ubiquitin-associated (UBA) domain in IAPs, which enables them to bind to Lys 63-linked polyubiquitin. We found that the UBA domain is essential for the oncogenic potential of cIAP1, to maintain endothelial cell survival and to protect cells from TNF-alpha-induced apoptosis. Moreover, the UBA domain is required for XIAP and cIAP2-MALT1 to activate NF-kappaB. Our data suggest that the UBA domain of cIAP2-MALT1 stimulates NF-kappaB signalling by binding to polyubiquitylated NEMO. Significantly, 98% of all cIAP2-MALT1 fusion proteins retain the UBA domain, suggesting that ubiquitin-binding contributes to the oncogenic potential of cIAP2-MALT1 in MALT lymphoma. Our data identify IAPs as ubiquitin-binding proteins that contribute to ubiquitin-mediated cell survival, NF-kappaB signalling and oncogenesis.
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PMID:IAPs contain an evolutionarily conserved ubiquitin-binding domain that regulates NF-kappaB as well as cell survival and oncogenesis. 1893 63

Malt1 is a multi-domain cytosolic signaling molecule that was originally identified as the target of recurrent translocations in a large fraction of MALT lymphomas. The product of this translocation is a chimeric protein in which the N-terminus is contributed by the apoptosis inhibitor, cIAP2, and the C-terminus is contributed by Malt1. Early studies suggested that Malt1 is an essential intermediate in antigen receptor activation of NF-kappaB, and that the juxtaposition of the cIAP2 N-terminus and the Malt1 C-terminus results in deregulation of Malt1 NF-kappaB stimulatory activity. Initial experimental data further suggested that the molecular mechanisms of Malt1- and cIAP-Malt1-mediated NF-kappaB activation were quite similar. However, a number of more recent studies of both Malt1 and cIAP2-Malt1 now reveal that these proteins influence NF-kappaB activation by multiple distinct mechanisms, several of which are non-overlapping. Currently available data suggest a revised model in which cIAP2-Malt1 induces NF-kappaB activation via a mechanism that depends equally on domains contributed by cIAP2 and Malt1, which confer spontaneous oligomerization activity, polyubiquitin binding, proteolytic activity, and association with and activation of TRAF2 and TRAF6 at several independent binding sites. By contrast, emerging data suggest that the wild-type Malt1 protein uniquely contributes to NF-kappaB activation primarily through the control of two proteolytic cleavage mechanisms. Firstly, Malt1 directly cleaves and inactivates A20, a negative regulator of the antigen receptor-to-NF-kappaB pathway. Secondly, Malt1 interacts with caspase-8, inducing caspase-8 cleavage of c-FLIP(L), initiating a pathway that contributes to activation of the I kappaB kinase (IKK) complex. Furthermore, data suggest that Malt1 plays a more limited and focused role in antigen receptor activation of NF-kappaB, serving to augment weak antigen signals and stimulate a defined subset of NF-kappaB dependent responses. Thus, the potent activation of NF-kappaB by cIAP2-Malt1 contrasts with the more subtle role of Malt1 in regulating specific NF-kappaB responses downstream of antigen receptor ligation.
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PMID:Malt1 and cIAP2-Malt1 as effectors of NF-kappaB activation: kissing cousins or distant relatives? 1977 15

Homologous to the E6-associated protein carboxyl terminus domain containing 3 (HECTD3) is an E3 ubiquitin ligase with unknown functions. Here, we show that HECTD3 confers cancer cell resistance to cisplatin. To understand the molecular mechanisms, we performed a yeast two-hybrid analysis and identified mucosa-associated lymphoid tissue 1 (MALT1) as an HECTD3-interacting protein. HECTD3 promotes MALT1 ubiquitination with nondegradative polyubiquitin chains by direct interacting with the MALT1 through its N-terminal destruction of cyclin domain. HECTD3 does not target MALT1 for degradation but stabilize it. HECTD3 depletion dramatically decreases the levels of MALT1 in MCF7 and HeLa cells treated with cisplatin, which is correlated to an increase in apoptosis. Knockdown of MALT1 likewise increases cisplatin-induced apoptosis in these cancer cells. However, HECTD3 over-expression leads to a decreased cisplatin-induced apoptosis, whereas overexpression of MALT1 partially rescues HECTD3 depletion-induced apoptosis. These findings suggest that HECTD3 promotes cell survival through stabilizing MALT1. Our data have important implications in cancer therapy by providing novel molecular targets.
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PMID:The HECTD3 E3 ubiquitin ligase suppresses cisplatin-induced apoptosis via stabilizing MALT1. 2335 72