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)

Binding of high risk human papillomavirus (HPV) E6 protein to E6-associated protein (E6AP), a cellular ubiquitin-protein ligase, enables E6AP to ubiquitinate p53, leading to p53 degradation in cervical cancer cells such as HeLa cells. Here we report that Pitx2a, a bicoid-type homeodomain transcription factor, can bind to HPV E6 protein and inhibit E6/E6AP-mediated p53 degradation. Deletion of the Pitx2a homeodomain abrogates its ability to bind to HPV E6 protein and to induce p53 accumulation in HeLa cells, suggesting that the homeodomain of Pitx2a is essential for inhibition of E6/E6AP-mediated p53 degradation. Recombinant Pitx2a can also block E6/E6AP-mediated p53 degradation in vitro, indicating that this function of Pitx2a is independent of its transcription activity. Pitx2a does not regulate Hdm2-mediated p53 degradation, because Pitx2a does not affect p53 protein levels in HPV-negative cells, such as HCT116, U2OS, and C33A cells. In addition, Pitx2a-induced p53 is transcriptionally active and maintains its specific DNA binding activity in HeLa cells. Taken together, these findings suggest that, by binding to E6, Pitx2a interferes with E6/E6AP-mediated p53 degradation, leading to the accumulation of functional p53 protein in HeLa cells.
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PMID:Pitx2a binds to human papillomavirus type 18 E6 protein and inhibits E6-mediated P53 degradation in HeLa cells. 1612 85

The ubiquitin conjugating system represents a rich source of potential molecular targets for cancer and other diseases. One target of great interest is the RING finger ubiquitin ligase (E3) Hdm2/Mdm2, which is frequently overexpressed in cancer and is a critical E3 for the tumor suppressor p53. For those 50% of tumors that express wild-type p53, agents that inhibit Hdm2 have great potential clinical utility. We summarize our ongoing efforts to identify inhibitors of Hdm2 E3 activity by high-throughput screening of both defined small molecules and natural product extracts. Employing a strategy using both enzymatic and cell-based assays, we have identified inhibitors that block the E3 activity of Hdm2, activate a p53 response, preferentially kill p53-expressing cells, and have the capacity to differentially cause death of transformed cells. Therefore, screening for inhibitors of Hdm2 ubiquitin ligase activity through in vitro assays represents a powerful means of identifying molecules that activate p53 in cancer cells to induce apoptosis. We also discuss the potential of inhibitors of ubiquitin-activating enzyme (E1) that were discovered during these screens. E1 inhibitors may similarly serve as the basis for novel therapeutics. Additionally, they represent unique tools for providing new insights into the ubiquitin conjugating system.
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PMID:Inhibiting Hdm2 and ubiquitin-activating enzyme: targeting the ubiquitin conjugating system in cancer. 1920 99

Malignant gliomas account for 35-45% of primary brain tumors; among these glioblastoma multiforme (GBM) is the most common adult brain tumor constituting approximately 85%. Its incidence is quite less in the pediatric population and treatment of these patients is particularly challenging. Exposure to ionizing radiation is the only environmental factor found to have any significant association with GBM. Several genetic alterations associated with GBM in adults have been well documented such as epidermal growth factor receptor amplification, overexpression of mouse double minute 2 homolog also known as E3 ubiquitin-protein ligase, Phosphatase and tensin homolog gene mutation, loss of heterozygosity of chromosome 10p and isocitrate dehydrogenase-1 mutation. However, data on genetic mutations in pediatric GBM is still lacking. Exophytic brain stem gliomas are rare tumors and are usually associated with a poor prognosis. The most effective treatment in achieving long-term survival in such patients, is surgical excision of the tumor and then chemoradiotherapy followed by adjuvant chemotherapy by temozolomide. This schedule is the standard treatment for GBM patients. In view of the rarity of pediatric GBM, we report here a case of pontine GBM in a 5-year-old girl.
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PMID:Variegated Colors of Pediatric Glioblastoma Multiforme: What to Expect? 2897 17