Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In acute promyelocytic leukaemia (APL), arsenic trioxide induces degradation of the fusion protein encoded by the PML-RARA oncogene, differentiation of leukaemic cells and produces clinical remissions. SUMOylation of its PML moiety was previously implicated, but the nature of the degradation pathway involved and the role of PML-RARalpha catabolism in the response to therapy have both remained elusive. Here, we demonstrate that arsenic-induced PML SUMOylation triggers its Lys 48-linked polyubiquitination and proteasome-dependent degradation. When exposed to arsenic, SUMOylated PML recruits RNF4, the human orthologue of the yeast SUMO-dependent E3 ubiquitin-ligase, as well as ubiquitin and proteasomes onto PML nuclear bodies. Arsenic-induced differentiation is impaired in cells transformed by a non-degradable PML-RARalpha SUMOylation mutant or in APL cells transduced with a dominant-negative RNF4, directly implicating PML-RARalpha catabolism in the therapeutic response. We thus identify PML as the first protein degraded by SUMO-dependent polyubiquitination. As PML SUMOylation recruits not only RNF4, ubiquitin and proteasomes, but also many SUMOylated proteins onto PML nuclear bodies, these domains could physically integrate the SUMOylation, ubiquitination and degradation pathways.
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PMID:Arsenic degrades PML or PML-RARalpha through a SUMO-triggered RNF4/ubiquitin-mediated pathway. 1845 29

In acute promyelocytic leukaemia (APL), the promyelocytic leukaemia (PML) protein is fused to the retinoic acid receptor alpha (RAR). This disease can be treated effectively with arsenic, which induces PML modification by small ubiquitin-like modifiers (SUMO) and proteasomal degradation. Here we demonstrate that the RING-domain-containing ubiquitin E3 ligase, RNF4 (also known as SNURF), targets poly-SUMO-modified proteins for degradation mediated by ubiquitin. RNF4 depletion or proteasome inhibition led to accumulation of mixed, polyubiquitinated, poly-SUMO chains. PML protein accumulated in RNF4-depleted cells and was ubiquitinated by RNF4 in a SUMO-dependent fashion in vitro. In the absence of RNF4, arsenic failed to induce degradation of PML and SUMO-modified PML accumulated in the nucleus. These results demonstrate that poly-SUMO chains can act as discrete signals from mono-SUMOylation, in this case targeting a poly-SUMOylated substrate for ubiquitin-mediated proteolysis.
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PMID:RNF4 is a poly-SUMO-specific E3 ubiquitin ligase required for arsenic-induced PML degradation. 1845 29

The FBXW7 (also known as AGO, hCDC4, FBW7 and SEL-10) gene encodes a subunit of an ubiquitin protein ligase which regulates levels of cyclin E, NOTCH and other proteins. Engineered FBXW7 null cells display cell cycle and chromosome stability defects. Mutations of FBXW7 have been found in human colorectal, ovarian, endometrial tumors and T-cell acute lymphocytic leukemias. Prompted by these findings we have examined acute myeloid leukemia, non-Hodgkin's lymphoma, T-cell acute lymphocytic leukemia, B-cell acute lymphocytic leukemia and adult T-cell leukemia DNA for mutations of the FBXW7 gene. Mutations were detected by PCR-SSCP of all coding exons of the three isoforms of FBXW7, shifted bands were direct sequenced. As expected, mutations were found in T-cell acute lymphocytic leukemias. However mutations of FBXW7 were also found in four of 118 B-cell acute lymphocytic leukemias and one of 24 adult T-cell leukemia samples. The nucleotide changes consisted of an insertion, resulting in a frameshift mutation, and missense mutations of highly conserved residues. All mutations affected the FBXW7 target interacting domain. These observations suggest that disruption of FBXW7 has a role in several forms of lymphocytic leukemias and not exclusively T-cell acute lymphocytic leukemia.
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PMID:FBXW7 mutation in adult T-cell and B-cell acute lymphocytic leukemias. 1848 78

A common feature of tumor cells is the aberrant expression of ion channels on their plasma membrane. The molecular mechanisms regulating ion channel expression in cancer cells are still poorly known. K(+) channels that belong to the human ether-a-go-go-related gene 1 (herg1) family are frequently misexpressed in cancer cells compared to their healthy counterparts. We describe here a posttranslational mechanism for the regulation of hERG1 channel surface expression in cancer cells. This mechanism is based on the activity of hERG1 isoforms containing the USO exon. These isoforms (i) are frequently overexpressed in human cancers, (ii) are retained in the endoplasmic reticulum, and (iii) form heterotetramers with different proteins of the hERG family. (iv) The USO-containing heterotetramers are retained intracellularly and undergo ubiquitin-dependent degradation. This process results in decreased hERG1 current (I(hERG1)) density. We detailed such a mechanism in heterologous systems and confirmed its functioning in tumor cells that endogenously express hERG1 proteins. The silencing of USO-containing hERG1 isoforms induces a higher I(hERG1) density in tumors, an effect that apparently regulates neurite outgrowth in neuroblastoma cells and apoptosis in leukemia cells.
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PMID:Identification of a posttranslational mechanism for the regulation of hERG1 K+ channel expression and hERG1 current density in tumor cells. 1855 21

Suppressor of cytokine signalling 3 (SOCS3) is responsible for regulating the cellular response to a variety of cytokines, including interleukin 6 and leukaemia inhibitory factor. Identification of the SOCS box domain led to the hypothesis that SOCS3 can associate with functional E3 ubiquitin ligases and thereby induce the degradation of bound signalling proteins. This model relies upon an interaction between the SOCS box, elonginBC and a cullin protein that forms the E3 ligase scaffold. We have investigated this interaction in vitro using purified components and show that SOCS3 binds to elonginBC and cullin5 with high affinity. The SOCS3-elonginBC interaction was further characterised by determining the solution structure of the SOCS box-elonginBC ternary complex and by deletion and alanine scanning mutagenesis of the SOCS box. These studies revealed that conformational flexibility is a key feature of the SOCS-elonginBC interaction. In particular, the SOCS box is disordered in isolation and only becomes structured upon elonginBC association. The interaction depends upon the first 12 residues of the SOCS box domain and particularly on a deeply buried, conserved leucine. The SOCS box, when bound to elonginBC, binds tightly to cullin5 with 100 nM affinity. Domains upstream of the SOCS box are not required for elonginBC or cullin5 association, indicating that the SOCS box acts as an independent binding domain capable of recruiting elonginBC and cullin5 to promote E3 ligase formation.
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PMID:The SOCS box domain of SOCS3: structure and interaction with the elonginBC-cullin5 ubiquitin ligase. 1859 Jul 40

The ubiquitin-proteasome system is the major pathway for intracellular protein degradation and is also deeply involved in the regulation of most basic cellular processes. Its proteolytic core, the 20S proteasome, has found to be attached also to the cell plasma membrane and certain observations are interpreted as to suggest that they may be released into the extracellular medium, e.g. in the alveolar lining fluid, epididymal fluid and possibly during the acrosome reaction. Proteasomes have also been detected in normal human blood plasma and designated circulating proteasomes; these have a comparatively low specific activity, a distinct pattern of subtypes and their exact origin is still enigmatic. In patients suffering from autoimmune diseases, malignant myeloproliferative syndromes, multiple myeloma, acute and chronic lymphatic leukaemia, solid tumour, sepsis or trauma, respectively, the concentration of circulating proteasomes has been found to be elevated, to correlate with the disease state and has even prognostic significance. Similarly, ubiquitin has been discovered as a normal component of human blood and seminal plasma and in ovarian follicular fluid. Increased concentrations were measured in diverse pathological situations, not only in blood plasma but also in cerebrospinal fluid, where it may have neuroprotective effects. As defective spermatozoa are covered with ubiquitin in the epididymal fluid, extracellular ubiquitination is proposed to be a mechanism for quality control in spermatogenesis. Growing evidence exists also for a participation of extracellular proteasomes and ubiquitin in the fertilization process.
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PMID:Extracellular, circulating proteasomes and ubiquitin - incidence and relevance. 1860 90

Flavonoids are polyphenolic compounds widely distributed in the plant kingdom. Compelling research indicates that flavonoids have important roles in cancer chemoprevention and chemotherapy possibly due to biological activities that include action through anti-inflammation, free radical scavenging, modulation of survival/proliferation pathways, and inhibition of the ubiquitin-proteasome pathway. Plant polyphenols including the green tea polyphenol (-)-epigallocatechin gallate or (-)-EGCG, and the flavonoids apigenin, luteolin, quercetin, and chrysin have been shown to inhibit proteasome activity and induce apoptosis in human leukemia cells. However, biotransformation reactions to the reactive hydroxyl groups on polyphenols could reduce their biological activities. Although methylated polyphenols have been suggested to be metabolically more stable than unmethylated polyphenols, the practical use of methylated polyphenols as cancer preventative agents warrants further investigation. In the current study, methylated and unmethylated flavonoids were studied for their proteasome-inhibitory and apoptosis-inducing abilities in human leukemia HL60 cells. Methylated flavonoids displayed sustained bioavailability and inhibited cellular proliferation by arresting cells in the G(1) phase. However, they did not act as proteasome inhibitors in either an in vitro system or an in silico model and only weakly induced apoptosis. In contrast, unmethylated flavonoids exhibited inhibition of the proteasomal activity in intact HL60 cells, accumulating proteasome target proteins and inducing caspase activation and poly(ADP-ribose) polymerase cleavage. We conclude that methylated flavonoids lack potent cytotoxicity against human leukemia cells and most likely have limited ability as chemopreventive agents.
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PMID:Relationship between the methylation status of dietary flavonoids and their growth-inhibitory and apoptosis-inducing activities in human cancer cells. 1863 46

BCL11A/EVI9 is a zinc-finger protein predominantly expressed in brain and hematopoietic cells. Previous studies show that BCL11A is involved in acute myelomonocytic leukemia and chronic lymphoid leukemia in mouse and human, respectively. Moreover, BCL11A is localized in the characteristic nuclear body in which BCL6 is co-localized. However, the significance of BCL11A in leukemogenesis and nuclear function remains unknown. In this study we show that BCL11A interacts with UBC9, a small ubiquitin-like modifier (SUMO) E2 conjugating enzyme, and recruits SUMO1 into the nuclear body. A lysine residue at amino acid 634 of BCL11A is SUMOylated but not required for the SUMO1 recruitment. The N-terminal region of BCL11A is responsible for SUMO1 recruitment as well as its nuclear body formation. We also show that SENP2, a SUMO specific peptidase, is co-localized in the nuclear body. These results suggest that BCL11A could be involved in the SUMO conjugation system, and that BCL11A might play an important role in protein modification.
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PMID:BCL11A is a SUMOylated protein and recruits SUMO-conjugation enzymes in its nuclear body. 1868 95

The article reviews Ubiquitin-26S proteasome system (UPS), which is an ATP-dependent protein degradation mechanism in eukaryotic cells. UPS effects many principal substrates and cellular processes, therefore, it is not surprising that aberrations in the system may be implicated in pathogenesis of many diseases. Alterations in the UPS are correlated with a variety of human pathologies, like cancer, immunological disorders, inflammation, neurodegenerative, liver diseases and etc. It is believed that ubiquitin cascade components E1, E2, E3, ubiquitin, proteasome, substrate protein, are useful in discover of new therapeutic possibilities. All kinds of aberrations have been found in ubiquitin-26S proteasome system, among them: truncated version of ubiquitin (Acute Lymphoblastic Leukaemia), elongated ubiquitin (Alcoholic Liver Disease), suppressed proteasome, accelerative degradation, decreased rates of degradation and etc. As irreversible course of cell cycle is very sensitive to protein degradation process, each of these derangements may cause proliferative disorders and hence development of heavy diseases. It is too difficult to identify a narrow window between benefits and toxicity of drugs used in treatment of different diseases. That is why is so important to discover inhibitors or activators of intracellular mechanisms for protein degradation due to development of targeted therapy.
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PMID:Ubiquitin-26s proteasome system. New therapeutic implications (review). 1871 Dec 38

Though there were a lot of reports about the totally different responses to the inhibition of ubiquitin-proteasome pathway in different kinds of cell lines, much less has been known about the responses in primary human leukemic cells. In this study, the effects of inhibition of ubiquitin-proteasome pathway on human bone marrow (BM) mononuclear cells (MNCs) obtained from 10 normal persons and 8 leukemia patients were examined. The results showed that the responses obviously varied individually. Among them, BM MNCs in 3 cases of leukemic patients were extremely sensitive, demonstrated by that > 90% cells were induced to undergo apoptosis within 24 h, but MNCs in 10 cases of normal persons showed resistance to the inhibition and no apoptosis was observed. Furthermore, Western blots revealed that the Bcl-2 expression was relatively high in the sensitive primary leukemia cells, and especially the cleavage of 26 ku Bcl-2 into a 22 ku fragment occurred during the induction of apoptosis. In contrast, the Bcl-2 expression was either undetectable or detectable but no cleavage of that above was observed in the cells insensitive to the inhibition of the pathway (including BM MNCs in normal persons). Together with the observations on the leukemic cell lines, these findings suggested the correlation of the specific cleavage of Bcl-2 into a shortened fragment with the sensitivity of cells to the inhibition of ubiquitin-proteasome pathway, which provides clues to the further understanding of the mechanisms of that dramatically different responses existing in different kinds of cells to the inhibition of ubiquitin-proteasome pathway.
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PMID:Effects of inhibition of ubiquitin-proteasome pathway on human primary leukemic cells. 1876 97


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