Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P10415 (Bcl-2)
 33,771 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Epstein-Barr virus (EBV) genome contains an open reading frame, BHRF1, that encodes a presumptive membrane protein with sequence similarity to the proto-oncogene bcl2, which is linked to human B-cell follicular lymphoma. Potential roles for BHRF1 in EBV's ability to growth transform human B cells and to replicate in B cells in culture were investigated by generating EBV mutants that lack most of the open reading frame. This was accomplished by recombination of plasmids carrying mutations in BHRF1 with the transformation-defective EBV strain P3HR1. Because BHRF1 resides close to the deletion in P3HR1 that renders this strain transformation defective, B-cell transformation could be used to select for recombination events in the region. B-cell clones were established by recombinants which lacked most of the BHRF1 open reading frame, although most of these initial B-cell transformants also carried nonrecombinant (BHRF1+) P3HR1 genomes, at levels ranging from a fraction of a copy to four copies per cell. Secondary B-cell transformants that lacked BHRF1+ EBV at detectable levels were found to release transforming, BHRF1-deficient EBV at levels that were within the normal range for EBV-immortalized B-cell clones. These studies demonstrate that BHRF1 is nonessential for growth transformation of B cells and for virus replication and release from these cells in culture.
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PMID:BHRF1 of Epstein-Barr virus, which is homologous to human proto-oncogene bcl2, is not essential for transformation of B cells or for virus replication in vitro. 131 10

The majority of non-Hodgkin's B-cell lymphomas contain a t(14;18) translocation that places the bc12 gene into juxtaposition with the transcriptically active Ig heavy-chain locus, thus deregulating the expression of this proto-oncogene. The bc12 gene product is a membrane-associated mitochondrial protein that regulates cell survival through unknown mechanisms. Although overproduction of the normal protein appears sufficient for conferring a selective growth or survival advantage to B cells, point mutations that alter the coding region of translocated bc12 genes have been described previously by others in a lymphoma cell line. However, it is not known whether somatic mutations that alter BCL2 proteins occur in vivo or whether they result from chemotherapy or arise through other mechanisms. For these reasons, we obtained DNA from the t(14;18)-containing tumors of five patients who had not undergone treatment for their disease, and used a polymerase chain reaction (PCR)-mismatch technique for rapid identification of point mutations in a portion of the bc12 open reading frame (ORF) corresponding to the first 131 aminoacids (aa) of the 239 aa p26 BCL2 protein. DNAs from two t(14;18)-containing cell lines were also analyzed. Point mutations in this region of the bc12 gene ORF were detected in three of five patients' tumors and in both cell lines. PCR-mismatch analysis of bc12 in cell lines and non-Hodgkin's lymphoma cases that lacked the t(14;18) translocation was negative, thus establishing the specificity of these results. DNA sequencing determined that these mutations are predicted to produce aa substitutions in the BCL2 proteins of two of the primary tumors and one of the cell lines. Interestingly, two of the patients contained an identical C----T transition that resulted in a nonconservative aa substitution (proline----serine) at position 59 of the BCL2 protein. Further analysis excluded the possibility that these mutations represented hereditary polymorphisms or PCR artifacts. A cluster of four point mutations within the translocation + bc12 allele of one patient had hallmarks of the somatic hypermutation mechanism that is associated with Ig genes and that contributes to antibody diversity. Because of the region of the bcl2 gene analyzed in these t(14;18) translocations is located nearly 300 kbp from the Ig heavy-chain locus, our data suggest that the Ig gene somatic hypermutation mechanism can act over extreme distances of DNA. It remains to be established whether these somatic mutations that alter BCL2 proteins influence the pathobiology of nonHodgkin's lymphomas.
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PMID:Frequent incidence of somatic mutations in translocated BCL2 oncogenes of non-Hodgkin's lymphomas. 133 99

B chronic lymphocytic leukemia (B-CLL) is characterized by the accumulation of slow-dividing and long-lived monoclonal B cells arrested at the intermediate stage of their differentiation. We previously showed that interleukin 4 (IL-4) not only inhibits but also prevents the proliferation of B-CLL cells. We report here that IL-4 protects the B-CLL cells from death by apoptosis (programmed cell death [PCD]). IL-4 inhibits spontaneous and hydrocortisone (HC)-induced PCD of highly purified B cells from 12 unselected CLL patients, as shown by sustained cell viability and lack of DNA fragmentation. IL-1, -2, -3, -5, -6, -7, tumor necrosis factor alpha, and transforming growth factor beta have no protective effect. The in vitro rescue from apoptosis by IL-4 is reflected by an increased expression of Bcl-2 protein, a proto-oncogene directly involved in the prolongation of cell survival in vivo and in vitro. Hence, IL-4-treated B-CLL cells express significantly more Bcl-2 than unstimulated, HC-treated, or fresh B-CLL cells. Furthermore, subcutaneous injection of IL-4 into one CLL patient enhances Bcl-2 protein expression in the leukemic B cells. These data may suggest that IL-4 prevents apoptosis of B-CLL cells using a Bcl-2-dependent pathway. Given our recent observations that fresh T cells from B-CLL patients express IL-4 mRNA, we propose that IL-4 has an essential role in the pathogenesis of CLL disease, by preventing both the death and the proliferation of the malignant B cells.
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PMID:Interleukin 4 protects chronic lymphocytic leukemic B cells from death by apoptosis and upregulates Bcl-2 expression. 140 78

Apoptosis is a form of physiological cell death, characterized by chromatin condensation, cytoplasmic blebbing and DNA fragmentation, which often depends on RNA and protein synthesis by the dying cell. The c-myc proto-oncogene, usually implicated in cell transformation, differentiation and cell-cycle progression also has a central role in some forms of apoptosis. These opposing roles of myc in cell growth and death require that other gene products dictate the outcome of c-Myc expression on a cell. A candidate for such a modifying gene is bcl-2, whose product prolongs cell survival and blocks apoptosis in some systems. Here we demonstrate that Bcl-2 prevents apoptotic death induced by c-Myc, provide a mechanism whereby cells can express c-Myc without undergoing apoptosis, and give a possible explanation for the ability of Bcl-2 to synergize with c-Myc in cell transformation.
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PMID:Apoptotic cell death induced by c-myc is inhibited by bcl-2. 140 75

The bcl-2 proto-oncogene is activated by translocation in a variety of B-lymphoid tumours and synergizes with the c-myc oncogene in tumour progression. The mechanism of synergy is unclear but bcl-2 expression inhibits apoptosis, a property presumably pertinent to its proto-oncogenic mode of action. We have shown that the c-myc gene is a potent inducer of apoptosis, in addition to its established role in mitogenesis. Here we show that expression of the bcl-2 protein, Bcl-2, specifically abrogates c-myc-induced apoptosis without affecting the c-myc mitogenic function. This provides a novel mechanism for oncogene cooperation, of potential importance both in carcinogenesis and in the evolution of drug resistance in tumours.
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PMID:Cooperative interaction between c-myc and bcl-2 proto-oncogenes. 140 76

Approximately half of the neurons produced during embryogenesis normally die before adulthood. Although target-derived neurotrophic factors are known to be major determinants of programmed cell death--apoptosis--the molecular mechanisms by which trophic factors interfere with cell death regulation are largely unknown. Overexpression of the bcl-2 proto-oncogene in cultured sympathetic neurons has now been shown to prevent apoptosis normally induced by deprivation of nerve growth factor. This finding, together with the previous demonstration of bcl-2 expression in the nervous system, suggests that the Bcl-2 protein may be a major mediator of the effects of neurotrophic factors on neuronal survival.
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PMID:Prevention of programmed cell death of sympathetic neurons by the bcl-2 proto-oncogene. 141 28

The proto-oncogene Bcl-2 is normally expressed in B lineage cells in a stage specific manner and extends cell survival. Deregulated Bcl-2 expression has been shown to cause a major expansion in surface IgM and IgD positive B cells. In this report, the influence of deregulated expression of Bcl-2 on the VH repertoire of B cells was studied. This was accomplished by stimulating B cells from both adult and fetal Bcl-2-Ig transgenic mice and their normal littermates using the polyclonal activator lipopolysaccharide. Activated cells were then analyzed by in situ hybridization using radiolabeled C mu and VH gene probes. The D-proximal VH families 7183 and Q52 were preferentially expressed in the adult transgenic mice compared to their normal littermates. VH 7183 and Q52 were also over-represented in fetal transgenic mice but not to a greater extent than that observed with normal fetuses. These results demonstrate that the overproduction of Bcl-2, which prolongs cell survival independent of affecting proliferation, substantially alters the VH gene repertoire.
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PMID:Skewed B cell VH family repertoire in Bcl-2-Ig transgenic mice. 177 25

The Bcl-2 proto-oncogene was discovered at the t(14;18) breakpoint found in most follicular B-cell lymphomas and some diffuse large-cell lymphomas. Bcl-2 is unique among proto-oncogenes, being localized to mitochondria and extending cell survival by blocking programmed cell death. We examined Bcl-2 protein expression in 82 hematologic malignancies and reactive lymphoid processes. All lymphomas with Bcl-2 rearrangement demonstrated high levels of Bcl-2 protein. However, most follicular and diffuse lymphomas without Bcl-2 rearrangement also displayed intense Bcl-2 staining. In these cases, mechanisms other than classic translocation may be deregulation Bcl-2. The pattern of Bcl-2 staining in follicular lymphoma is the inverse of the pattern in reactive hyperplasia, confirming a role for Bcl-2 immunolocalization in routine diagnosis. Small lymphocytic malignancies, including small lymphocytic lymphoma, mantle zone lymphoma, and chronic lymphocytic leukemia, expressed intermediate levels of Bcl-2. Bcl-2 protein varied in plasma cell dyscrasias. Bcl-2 protein levels in T-cell lymphomas reflected their corresponding stage of development. No substantial Bcl-2 was present in the Reed-Sternberg cells of nodular sclerosing Hodgkin's disease. Chronic myelogenous leukemia was strongly positive for Bcl-2, consistent with the presence of Bcl-2 in normal myeloid progenitors. Immunohistochemistry identified an expanded spectrum of hematopoietic neoplasms in which Bcl-2 may provide a cell survival advantage.
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PMID:Immunolocalization of the Bcl-2 protein within hematopoietic neoplasms. 186 40

The number of lymphocytes in an animal is remarkably constant despite antigen-driven proliferation and a high rate of B-cell lymphopoiesis. This reflects the relatively brief lifespan of many newly generated B cells and argues for a well-regulated death mechanism. Even so, a secondary immune response can be generated years after a primary exposure to antigen. Antigen that might restimulate B cells persists for extended periods on follicular dendritic cells in the light zone of germinal centres. Antigen-binding B cells have also been found months after the end of obvious cell division. The precise signal that enables certain B cells to emerge as long-term surviving memory cells is unknown. Bcl-2, an inner mitochondrial membrane protein, blocks programmed cell death in B cells. We report here that this proto-oncogene maintains immune responsiveness. Transgenic mice overproducing Bcl-2 have a long-term persistence of immunoglobulin-secreting cells and an extended lifetime for memory B cells.
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PMID:Bcl-2 maintains B cell memory. 190 51

We characterized the basis for the follicular lymphoproliferation in transgenic mice bearing a Bcl-2-immunoglobulin (Bcl-2-Ig) minigene representing the t(14;18) of human follicular lymphoma. Discriminatory S1 nuclease protection assays revealed that the Bcl-2-Ig transgene was overexpressed relative to endogenous mouse Bcl-2 in spleen and thymus. Western (immunoblot) analysis demonstrated the overproduction of the human 25-kilodalton Bcl-2 protein, which arose from the transgene, in spleen, thymus, and the expanded B-cell subset. Despite the generalized lymphoid pattern of deregulation, two-color flow cytometry and density gradient centrifugation indicated that the expanded lymphocytes were predominantly small, resting B cells coexpressing B220, immunoglobulin M (IgM), IgD, Ia, and kappa. Cell cycle analysis confirmed that about 97% of these expanded B cells reside in G0/G1. An extensive characterization of transgenic lines revealed a fourfold excess of IgM-IgD-expressing B cells in spleen and dramatically increased numbers in bone marrow. While resting, these cells proliferated in response to lipopolysaccharide and anti-IgM and demonstrated normal B-cell colony formation in soft agar. Moreover, these B cells, which demonstrated an extended survival in vitro even in the absence of stroma, were also resting in G0, yet were capable of proliferative responses. These findings provide consistent evidence that the accumulation of B cells after Bcl-2 overproduction is secondary to prolonged cell survival and not increased cell cycling. This suggests a unique role for Bcl-2 as a proto-oncogene that enhances cell survival independent of promoting cell division.
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PMID:Deregulated Bcl-2-immunoglobulin transgene expands a resting but responsive immunoglobulin M and D-expressing B-cell population. 218 11


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