Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.3.2.19 (ubiquitin-protein ligase)
 799 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During apoptosis, Smac (second mitochondria-derived activator of caspases)/DIABLO, an IAP (inhibitor of apoptosis protein)-binding protein, is released from mitochondria and potentiates apoptosis by relieving IAP inhibition of caspases. We demonstrate that exposure of MCF-7 cells to the death-inducing ligand, TRAIL (tumor necrosis factor-related apoptosis-inducing ligand), results in rapid Smac release from mitochondria, which occurs before or in parallel with loss of cytochrome c. Smac release is inhibited by Bcl-2/Bcl-xL or by a pan-caspase inhibitor demonstrating that this event is caspase-dependent and modulated by Bcl-2 family members. Following release, Smac is rapidly degraded by the proteasome, an effect suppressed by co-treatment with a proteasome inhibitor. As the RING finger domain of XIAP possesses ubiquitin-protein ligase activity and XIAP binds tightly to mature Smac, an in vitro ubiquitination assay was performed which revealed that XIAP functions as a ubiquitin-protein ligase (E3) in the ubiquitination of Smac. Both the association of XIAP with Smac and the RING finger domain of XIAP are essential for ubiquitination, suggesting that the ubiquitin-protein ligase activity of XIAP may promote the rapid degradation of mitochondrial-released Smac. Thus, in addition to its well characterized role in inhibiting caspase activity, XIAP may also protect cells from inadvertent mitochondrial damage by targeting pro-apoptotic molecules for proteasomal degradation.
 ...
PMID:Proteasome-mediated degradation of Smac during apoptosis: XIAP promotes Smac ubiquitination in vitro. 1212 69

Pirh2, a recently identified ubiquitin-protein ligase, has been reported to promote p53 degradation. Pirh2 physically interacts with p53 and promotes ubiquitination of p53 independently of MDM2. Like MDM2, Pirh2 is thought to participate in an autoregulatory feedback loop that controls p53 function. We have previously reported that Pirh2 was overexpressed in human and murine lung cancers as compared to uninvolved lung tissue. Pirh2 increase could potentially cause degradation of wildtype p53 and reduce its tumor suppression function in the lung tumor cells. Since Pirh2 has been reported to be transactivated by p53, however, the mechanisms by which a high level of Pirh2 expression is maintained in tumor cells despite low level of wildtype p53 protein are unclear. In order to evaluate p53 involvement in the transactivation of Pirh2, we evaluated Pirh2, MDM2, p53 and p21 expression with Western blot analysis and real time PCR after gamma irradiation or cisplatin DNA damage treatment using human cancer cell lines containing wildtype (A549, MCF-7), mutant (H719) and null (H1299) p53. Surprisingly, Pirh2 expression was not affected by the presence of wildtype p53 in the cancer cells. In contrast, MDM2 was upregulated by wildtype p53 in A549 and MCF-7 cells and was absent from the H1299 and the H719 cells. We conclude that Pirh2 operates in a distinct manner from MDM2 in response to DNA damage in cancer cells. Pirh2 elevation in p53 null cells indicates the existence of additional molecular mechanisms for Pirh2 upregulation and suggests that p53 is not the sole target of Pirh2 ubiquitin ligase activity.
 ...
PMID:Differential response between the p53 ubiquitin-protein ligases Pirh2 and MdM2 following DNA damage in human cancer cells. 1693

The present study was undertaken to investigate the anticancer activity of methyl caffeate isolated from Solanum torvum Swartz. fruit and to explore the molecular mechanisms of action in MCF-7 cells. Cytotoxic properties of hexane, ethyl acetate and methanol extracts were carried out against MCF-7 cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Ethyl acetate extract showed good cytototoxic activities compared to hexane and methanol extracts. Methyl caffeate was isolated from the ethyl acetate extract using column chromatography. Cytotoxic properties of methyl caffeate was investigated against MCF-7, A549, COLO320, HepG-2 and Vero cells. The compound showed potent cytotoxic properties against MCF-7 cells compared to A549, COLO320 and HepG-2 cells. Methyl caffeate significantly reduced cell proliferation and increased formation of fragmented DNA and apoptotic body in MCF-7 cells. Bcl-2, Bax, Bid, p53, caspase-3, PARP and cytochrome c release were detected by western blot analysis. The activities of caspases-3 and PARP gradually increased after the addition of isolated compound. Bcl-2 protein was down regulated; Bid and Bax were up regulated after the treatment with methyl caffeate. Molecular docking studies showed that the compound bound stably to the active sites of poly (ADP-ribose) polymerase-1 (PARP1), B cell CLL/lymphoma-2 (BCL-2), E3 ubiquitin-protein ligase (MDM2) and tubulin. The results strongly suggested that methyl caffeate induced apoptosis in MCF-7 cells via caspase activation through cytochrome c release from mitochondria.
 ...
PMID:In vitro anticancer activity of methyl caffeate isolated from Solanum torvum Swartz. fruit. 2641 18

Kinesin spindle protein (KSP) is a microtubule-associated motor protein that is specifically expressed by mitosis cells. It is highly expressed in various types of tumors including hematomalignances and solid tumors. Chemical KSP inhibition has become a novel strategy in the development of anticancer drugs. SB743921 is a selective inhibitor for KSP, which is a mitotic protein essential for cell-cycle progression. Although SB743921 has shown antitumor activities for several types of cancers and entered into clinical trials, its therapeutic effects on breast cancer and mechanisms have not been explored. In this study, we tested the antitumor activity of SB743921 in breast cancer cell lines and partly elucidated its mechanisms. KSP and denticleless E3 ubiquitin-protein ligase homolog (DTL) are overexpressed in breast cancer cells compared with no-cancer tissues. Chemical inhibition of KSP by SB743921 not only reduces proliferation but also induces cell-cycle arrest and leads to apoptosis in breast cancer cells. Treatment of MCF-7 and MDA-MB-231 breast cancer cell lines with SB743921 results in decreased ability of colony formation in culture. SB743921 treatment also causes a KSP accumulation in protein level that is associated with cell arrest. Furthermore, we showed that SB743921 treatment significantly reduces the expression of bcl-2 and cell cycle-related protein DTL, and upregulates p53 and caspase-3 in breast cancer cells. Taken together, these data indicated that SB743921 can be expected to be a novel treatment agent for breast cancers.
 ...
PMID:KSP inhibitor SB743921 inhibits growth and induces apoptosis of breast cancer cells by regulating p53, Bcl-2, and DTL. 2737 29

Sal-like 4 (SALL4) is a transcription factor that enhances proliferation and migration in breast cancer cells. SALL4 expression therefore has the potential to promote cancer malignancy. However, the regulatory mechanisms involved in SALL4 protein expression have not been thoroughly elucidated. In this study, we observed that treating MCF-7 and SUM159 breast cancer cell lines with a proteasome inhibitor increases SALL4 protein levels, suggesting that SALL4 is degraded by the ubiquitin-proteasome system. Using immunoprecipitation to uncover SALL4-binding proteins, we identified an E3 ubiquitin-protein ligase, tripartite motif-containing 21 (TRIM21). Using an EGFP reporter probe of the major SALL4 isoform SALL4B, we observed that shRNA-mediated knockdown of TRIM21 increases cellular SALL4B levels. Immunostaining experiments revealed that TRIM21 localizes to the nucleus, and a K64R substitution in the nuclear localization motif in SALL4B increased SALL4B levels in the cytoplasm. These results suggested that TRIM21 is involved in nuclear SALL4 degradation. To identify the amino acid residue that is targeted by TRIM21, we fragmented the SALL4B sequence, fused it to EGFP, and identified Lys-190 in SALL4B as TRIM21's target residue. Amino acid sequence alignments of SALL family members indicated that the region around SALL4 Lys-190 is conserved in both SALL1 and SALL3. Because SALL1 and SALL4 have similar functions, we constructed a SALL1-EGFP probe and found that the TRIM21 knockdown increases SALL1 levels, indicating that TRIM21 degrades both SALL1 and SALL4. Our findings extend our understanding of SALL4 and SALL1 regulation and may contribute to the development of SALL4-targeting therapies.
 ...
PMID:Sal-like 4 protein levels in breast cancer cells are post-translationally down-regulated by tripartite motif-containing 21. 2951 Oct 85