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Query: UNIPROT:P10415 (Bcl-2)
 33,771 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Most examples of cell death in animals are controlled by a genetic program that is activated within the dying cell. The apoptotic process is further regulated by a set of genes that act as repressors of cell death. Of these, bcl-2 is expressed in a variety of embryonic and postnatal tissues which suggests a critical role for bcl-2 in organogenesis and tissue homeostasis. Surprisingly, mutant mice with targeted disruption of bcl-2 appear normal at birth and complete maturation of lymphoid tissues before succumbing to fulminant lymphopenia and polycystic renal disease by 2-5 weeks of age. This suggests that there may be genes other than bcl-2 that can regulate apoptosis during development. To begin to investigate this possibility, we have cloned and characterized the murine bcl-x gene, whose human counterpart displays striking homology to bcl-2. The predicted murine bcl-xL gene product exhibits a high level of amino acid identity (97%) to its human counterpart. Just like Bcl-2, the murine bcl-xL gene product can act as a dominant inhibitor of cell death upon growth factor withdrawal. In addition, the bulk of the bcl-xL product localizes to the periphery of mitochondria as assessed by a bcl-xL-tag expression system, suggesting that both Bcl-2 and Bcl-xL proteins prevent cell death by a similar mechanism. bcl-xL is the most abundant bcl-x mRNA species expressed in embryonic and adult tissues. The levels of bcl-xL mRNA appear higher than those of bcl-2 during embryonal development and in several adult organs including bone marrow, brain, kidney and thymus. In addition to bcl-xL, we have identified another form of bcl-x mRNA, bcl-x beta, that results from an unspliced bcl-x transcript. bcl-x beta mRNA is expressed in various embryonic and postnatal tissues. Surprisingly, the expression of bcl-xS (a negative regulator of programmed cell death) was undetectable by a sensitive S1-nuclease assay and polymerase chain reaction analysis of mouse tissues. Based on its tissue and developmental patterns of expression, it appears that bcl-x may play an important role in the regulation of cell death during development and tissue homeostasis.
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PMID:bcl-XL is the major bcl-x mRNA form expressed during murine development and its product localizes to mitochondria. 760 90

The control of cell survival is of central importance in tissues with high cell turnover such as the lymphoid system, and its disruption may be a critical step in tumorigenesis. Genes homologous to bcl-2, the oncogene implicated in human follicular lymphoma, play a key role in regulating physiologic cell death (apoptosis). Bcl-2 and its relatives bcl-x and bax encode intracellular membrane-bound proteins that share homology in three domains with a wider family of viral and cellular proteins. The Bcl-2 and Bcl-x proteins enhance the survival of lymphocytes and other cell types but do not promote their proliferation. High levels of Bax or of a smaller Bcl-x variant antagonize the survival function of Bcl-2. The mechanism by which Bcl-2 promotes cell survival remains unknown, but it appears to require association with Bax. Bcl-2 may combat the action of cysteine proteases thought to trigger apoptosis. Bcl-2 is not essential for embryogenesis or lymphoid development. However, upregulation of Bcl-2 appears to be the normal mechanism for positive selection of developing lymphocytes, and its continued expression is critical for survival of mature peripheral B and T cells. Constitutive expression of Bcl-2 does not abrogate deletion of self-reactive lymphocytes, nor disturb T lymphoid homeostasis; however, it substantially increases the pool of mature noncycling B cells. The risk of B lymphoid tumors is also enhanced, probably because Bcl-2 can countermand the apoptotic action of other oncoproteins such as Myc. Expression in tumors of bcl-2 and other cell survival genes may constitute a major barrier to the success of genotoxic cancer therapy.
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PMID:Regulation of lymphocyte survival by the bcl-2 gene family. 761 33

t(14;18) is the most common translocation in human lymphoid malignancy and results in bcl-2 overexpression. Bcl-2 blocks apoptosis and constitutes the initial member of a new category of oncogenes, ie, regulators of cell death. Bcl-2-Ig transgenic mice develop follicular hyperplasia and progress to malignant B-cell lymphoma. To assess the oncogenic potential of bcl-2 in the T-cell lineage, a cohort of 68 lckpr-bcl-2 transgenic mice and 56 control littermates were monitored for signs of malignancy over a 24-month period. Eighteen (26%) lckpr-bcl-2 mice developed diffuse, predominantly large-cell lymphomas at a mean age of 18 months. In contrast, only one nontransgenic control mouse developed lymphoma. CD3 surface expression and clonal T-cell receptor beta rearrangements support the T-lineage classification of these neoplasms. lckpr-bcl-2-enforced lymphomas are predominantly CD4+CD8-, consistent with a mature peripheral T-cell phenotype. These data provide support for the thesis that violation of homeostasis through the repression of cell death can be a primary mechanism of tumorigenesis in multiple lineages.
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PMID:Peripheral T-cell lymphoma in lckpr-bcl-2 transgenic mice. 763 29

Discordant morphology between lymph node or extra-nodal site and bone marrow (BM) involvement by non-Hodgkin's malignant lymphoma (NHL) is a common occurrence, causing diagnostic difficulties. Additional diagnostic problems are posed by lymphoid aggregates commonly found in the BM of elderly patients, the age group with the highest incidence of lymphoma. Morphologic features are used to distinguish between benign and malignant lesions but no feature is diagnostic and exceptions are numerous. Immunophenotyping is helpful for detecting B cell monoclonality, but it cannot detect T cell monoclonality. Unique B and T cell gene rearrangement patterns, the molecular "signature" of the lymphoma, can be used to detect monoclonal lymphoid populations. Finding the same rearrangement pattern in the BM as in the primary mass is proof of BM involvement by the same clone of malignant cells. We used B/T and Bcl-2 gene rearrangements to help diagnose cases with discordant morphology between primary site and BM. One hundred and seventy-five specimens, obtained from patients undergoing staging or restaging for NHL, were analyzed for B/T cell and Bcl-2 gene rearrangements by multiple restriction endonuclease digestion and Southern hybridization with 32P labeled JH, JK, CT beta, and Bcl-2 probes. Forty-two specimens (24%) from 24 patients showed discordant morphology: of 13 specimens with atypical lymphoid aggregates, only one had B cell gene rearrangement; of 15 specimens with morphologically benign lymphoid aggregates, one demonstrated B cell gene rearrangement; and of 14 specimens positive for NHL with different morphology than the lymph node, 13 were positive for B cell gene rearrangements. Molecular analysis can aid in the diagnosis of NHL, can establish a "baseline" for detection of recurrence, and is useful in monitoring therapy. These data suggest that it is also a tool for the pathologist in cases of discordant morphology between the primary tumor and BM, and should be strongly considered for each site.
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PMID:Discordant morphologic features in bone marrow involvement by malignant lymphomas: use of gene rearrangement patterns for diagnosis. 763 75

The antiapoptosis potential of Bcl-2 protein is well established, but the mechanism of Bcl-2 action is still poorly understood. Using the phosphatase inhibitor okadaic acid or the chemotherapeutic drug taxol, we found that Bcl-2 was phosphorylated in lymphoid cells. Phospho amino acid analysis revealed that Bcl-2 was phosphorylated on serine. Under similar conditions, okadaic acid or taxol treatment led to the induction of apoptosis in these cells. Thus, phosphorylation of Bcl-2 seems to inhibit its ability to interfere with apoptosis. In addition, phosphorylated Bcl-2 can no longer prevent lipid peroxidation as required to protect cells from apoptosis.
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PMID:Inactivation of Bcl-2 by phosphorylation. 775 34

Bcl-2 protein expression has been found to block apoptosis and its overexpression has been implicated in lymphoid malignancies where the chromosomal translocation t(14;18) is present. In this study we investigated bcl-2 transcription and protein expression in cultured cervical carcinoma cell lines and keratinocytes. Western blotting and immunofluorescence microscopy demonstrated bcl-2 expression in the cytoplasm of 4 out of 5 cervical carcinoma cell lines examined (HeLa, CaSki, C-33A, and HT-3, but not SiHa). Bcl-2 protein expression was undetectable in normal keratinocytes. None of the cell lines examined demonstrated chromosomal translocation or rearrangement at the major breakpoint-cluster region (MBR) of the bcl-2 gene using either Southern blot or polymerase chain reaction (PCR) analyses. Northern blot analysis demonstrated low levels of bcl-2 transcription in HeLa, CaSki, and C-33A cell lines while reverse transcriptase (RT)-PCR demonstrated bcl-2 transcription in all cervical carcinoma cell lines which had bcl-2 protein expression. Thus, these data suggest that bcl-2 expression occurs in cervical carcinoma cell lines in the absence of chromosomal translocation or rearrangement of the bcl-2 gene. However, each of these cervical carcinoma cell lines contains inactive p53, either due to mutation (C-33A and HT-3) or via complexation and degradation with human papillomavirus (HPV) 16/18 E6 protein (HeLa and CaSki). Thus, functional p53, which can induce apoptosis in certain cells, is not present in these cervical cells which have increased bcl-2 expression. Increased bcl-2 expression under conditions of p53 inactivation may provide cells with a selective advantage for survival and consequently play a role in the development of cervical carcinogenesis.
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PMID:Bcl-2 protooncogene expression in cervical carcinoma cell lines containing inactive p53. 776 85

It has been postulated that the high levels of autoantibodies observed in systemic lupus erythematosus (SLE) patients could result from abnormal longevity of polyclonally activated B-cells. This increased survival could be due to dysfunction of apoptosis, the normal regulatory process governing their life span. The protein product of the bcl-2 gene can enhance lymphoid cell survival by interfering with apoptosis. Moreover, transgenic mice overexpressing bcl-2 in their B-cells developed an autoimmune syndrome resembling SLE. To determine whether overexpression of bcl-2 occurs in SLE patients, bcl-2 protein was measured in peripheral blood mononuclear cells from 73 SLE patients, 20 healthy individuals and 47 patients with other autoimmune diseases. Only three lupus patients had raised levels of bcl-2 and there were no statistically significant differences in the mean bcl-2 levels measured in SLE patients compared to controls. Bcl-2 levels did not correlate with overall disease activity in SLE patients.
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PMID:Bcl-2 expression is unaltered in unfractionated peripheral blood mononuclear cells in patients with systemic lupus erythematosus. 778 44

To study molecular mechanisms underlying neuronal cell death, we have used sympathetic neurons from superior cervical ganglia which undergo programmed cell death when deprived of nerve growth factor. These neurons have been microinjected with expression vectors containing cDNAs encoding selected proteins to test their regulatory influence over cell death. Using this procedure, we have shown previously that sympathetic neurons can be protected from NGF deprivation by the protooncogene Bcl-2. We now report that the E1B19K protein from adenovirus and the p35 protein from baculovirus also rescue neurons. Other adenoviral proteins, E1A and E1B55K, have no effect on neuronal survival. E1B55K, known to block apoptosis mediated by p53 in proliferative cells, failed to rescue sympathetic neurons suggesting that p53 is not involved in neuronal death induced by NGF deprivation. E1B19K and p35 were also coinjected with Bcl-Xs which blocks Bcl-2 function in lymphoid cells. Although Bcl-Xs blocked the ability of Bcl-2 to rescue neurons, it had no effect on survival that was dependent upon expression of E1B19K or p35.
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PMID:Viral proteins E1B19K and p35 protect sympathetic neurons from cell death induced by NGF deprivation. 782 15

Epstein-Barr virus (EBV) is associated with tumours of both lymphoid and epithelial origin. Whilst a role for EBV latent genes in the development of these malignancies is accepted, it is also possible that viral proteins involved in EBV replication may influence the oncogenic process. BHRF1 is an immediate early protein which has homology with the Bcl-2 oncogene and can protect B cells from apoptosis. In vivo this protein is most abundantly expressed in the upper layers of oral 'hairy' leukoplakia (HL), a benign hyperparakeratotic tongue lesion which represents a focus EBV replication. We have transfected BHRF1 into the human squamous cell carcinoma line SCC12F which retains several features of normal keratinocytes behaviour in vitro. BHRF1 expression in these epithelial cells is associated with a delay in the commitment of cells to terminal differentiation, increased resistance to the DNA damaging drug, cis-platin and enhanced survival under conditions of serum deprivation. As the differentiation of epithelial cells is an apoptotic process, this data strongly suggests that BHRF1 expression delays the terminal differentiation of epithelial cells through the prevention of apoptosis. This effect of BHRF1, which may normally function to promote productive EBV infection, could contribute to the development of EBV-associated tumours.
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PMID:BHRF1, a viral homologue of the Bcl-2 oncogene, disturbs epithelial cell differentiation. 782 80

Using a protein interaction cloning technique, we identified cDNAs that encode a novel Bcl-2-binding protein, termed BAG-1. The BAG-1 protein shares no significant homology with Bcl-2 or other Bcl-2 family proteins, which can form homo- and heterodimers. In gene transfer experiments using a human lymphoid cell line, Jurkat, coexpression of BAG-1 and Bcl-2 provided markedly increased protection from cell death induced by several stimuli, including staurosporine, anti-Fas antibody, and cytolytic T cells, relative to cells that contained gene transfer-mediated elevations in either BAG-1 or Bcl-2 protein alone. BAG-transfected 3T3 fibroblasts also exhibited prolonged cell survival in response to an apoptotic stimulus. The findings indicate that bag-1 represents a new type of anti-cell death gene and suggest that some routes of apoptosis induction previously ascribed to Bcl-2-independent pathways may instead reflect a need for the combination of Bcl-2 and BAG-1.
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PMID:Cloning and functional analysis of BAG-1: a novel Bcl-2-binding protein with anti-cell death activity. 783 47


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