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

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

The bcl-2 gene was first discovered by molecular analysis of the 14;18 chromosome translocation which is the hallmark of most cases of human follicular lymphoma. To date, it is unique among proto-oncogenes because, rather than promoting cell proliferation, it fosters cell survival. This review summarizes the impact of constitutive bcl-2 expression on the development and function of lymphocytes as well as their malignant transformation. Expression of a bcl-2 transgene in the B lymphoid compartment profoundly perturbed homeostasis and, depending on the genetic background, predisposed to a severe autoimmune disease resembling human systemic lupus erythematosus. T lymphoid cells from bcl-2 transgenic mice were remarkably resistant to diverse cytotoxic agents. Nevertheless, T lymphoid homeostasis was unaffected and tolerance to self was maintained. Expression of high levels of Bcl-2 facilitated the development of B lymphoid tumours but at relatively low frequency and with long latency. Co-expression of myc and bcl-2, on the other hand, promoted the rapid onset of novel tumours which appeared to derive from a lympho-myeloid stem or progenitor cell. Introduction of the bcl-2 transgene into scid mice facilitated the survival and differentiation of pro-B but not pro-T cells, suggesting that a function necessary to supplement or complement the action of Bcl-2 is expressed later in the T than the B lineage. Crosses of the bcl-2 transgenic mice with p53-/- mice have addressed whether loss of p53 function and gain of bcl-2 function are synergistic for lymphoid cell survival.
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PMID:Insights from transgenic mice regarding the role of bcl-2 in normal and neoplastic lymphoid cells. 784 27

The v-Rel oncoprotein of the avian Rev-T retrovirus malignantly transforms chicken spleen cells in vivo and in vitro. We previously described two temperature-sensitive (ts) mutants of v-Rel (v-G37E and v-R273H) that show a ts ability to transform chicken spleen cells and to bind to DNA in vitro. We now show that spleen cell lines transformed by ts v-Rel proteins at the permissive temperature undergo apoptosis when cells are shifted to the nonpermissive temperature. The levels of most proteins (including v-Rel, p53, c-Myc, Rb and Bcl-2) do not change in these cells even at advanced stages of apoptosis. However, the chicken I kappa B-alpha protein (also called p40), which is in a complex with v-Rel in transformed cells, is degraded when ts v-Rel-transformed cells are shifted to the nonpermissive temperature. In v-R273H-transformed cells, p40 is degraded without the appearance of proteolytic intermediates. In contrast, in v-G37E-transformed cells, p40 is cleaved to an intermediate species that is missing approximately 3-4 kDa from its amino terminus. This truncated form of p40 is found in a detergent-insoluble fraction and can also be detected in wild-type v-Rel-transformed cells that are induced to undergo apoptosis by treatment with cycloheximide. Both ts v-Rel proteins are ts for interaction with p40 in vitro. The results reported here indicate that v-Rel blocks a normal pathway of programmed cell death and that I kappa B-alpha can undergo multiple degradative pathways, which can be induced by alterations in the structure of the Rel protein to which it is bound.
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PMID:The v-Rel oncoprotein blocks apoptosis and proteolysis of I kappa B-alpha in transformed chicken spleen cells. 789 28

The roles of p53 as an inducer and Bcl-2 as an inhibitor of apoptotic death were explored in lymphoid cells. Lymphocytes from p53-/- mice were radioresistant, but unexpectedly, cycling T lymphoma cells and mitogenically activated T lymphocytes from these animals underwent apoptosis after irradiation or genotoxic drug treatment. Hence, p53 is not the only mediator of apoptosis provoked by DNA damage. Irradiated p53-/- lymphoblasts expressing Bcl-2 were subject to growth arrest but resisted apoptosis. Their accumulation in G1 as well as G2 is suggestive of a p53-independent DNA-damage G1 checkpoint. Since Bcl-2 increased the clonogenic survival of the irradiated cells, expression of survival genes may pose a greater impediment to genotoxic cancer therapy than loss of p53.
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PMID:DNA damage can induce apoptosis in proliferating lymphoid cells via p53-independent mechanisms inhibitable by Bcl-2. 795 87

DNA-damaging agents such as ionizing radiation (IR) activate the tumor suppressor p53 and in some cases can cause apoptosis. M1 cells, which do not express the endogenous tumor suppressor gene p53, undergo apoptosis following activation of a temperature sensitive p53 transgene, where it has been shown that bax, an important mediator of apoptosis, is a p53 target gene (Selvakumaran et al, Oncogene 9, 1791-8, 1994). Since p53 can function as a transcription factor after activation by IR, the genetic response to this stress was examined in a panel of human cells with defined p53 status. Like the p53-regulated gene gadd45, bax was rapidly induced, as measured by increased mRNA levels, in the p53 wt (wild type) human myeloid line ML-1, and it was not induced in cells lacking functional p53. However, unlike other p53-regulated genes, bax was only induced in p53 wt cells in which IR also triggered apoptosis. In the case of bcl2, which opposes bax function, mRNA levels were reduced in ML-1 cells after IR. Thus, bax appears to be an unique p53-regulated gene in that its induction by IR not only requires functional p53 but also requires that the cells be apoptosis "proficient."
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PMID:Induction of bax by genotoxic stress in human cells correlates with normal p53 status and apoptosis. 797 Jul 35

Bcl-2 gene product functions to prevent apoptosis in a variety of in vitro and in vivo experiments. The prognostic significance of Bcl-2 protein expression was investigated by immunocytochemistry from paraffin-embedded tissue in a series of 174 women with breast cancer, treated with radical surgery with or without regional radiotherapy, and who had been followed up for the median of 31 years or until death. A minority (25%) of cancers were entirely negative for Bcl-2 protein. Moderate to strong Bcl-2 protein expression (present in 46%) was strongly associated with several favorable prognostic features, such as a low mitotic count, high histological grade of differentiation, and lack of p53 protein expression (P < 0.0001 for each). It was also significantly associated with lack of tumor necrosis, a low S-phase fraction size, low cathepsin D expression, DNA diploidy, and the lobular histological type, but not with the primary tumor size or the axillary nodal status. Women with cancer with moderate to strong Bcl-2 protein expression had more favorable short-term (69% versus 46% alive at 5 years) but similar long-term (29% versus 33% alive at 30 years) disease-specific survival as those with cancer with weak or lacking expression. Bcl-2 protein expression did not have independent prognostic value in a multivariate survival analysis. We conclude that Bcl-2 protein is frequently expressed in breast cancer, and its expression is associated with favorable clinicopathological features.
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PMID:Bcl-2 protein expression and long-term survival in breast cancer. 797 49

We have studied the ability of c-myc and bcl-2 oncogenes to modulate p53 function. Our studies show that coincident expression of human Bcl-2 protein with p53 prolongs survival of murine erythroleukemia cells. This effect was associated with a loss of the G1 specificity of p53-mediated cell cycle arrest. Furthermore, we found that the c-myc and bcl-2 genes cooperate to inhibit p53 functions. Coexpression of bcl-2 and c-myc can totally overcome p53-induced apoptosis and cell cycle arrest by altering the subcellular trafficking of p53 during the cell cycle: the p53 remains in the cytoplasm of the cotransfected cells during a critical period in G1. This finding suggests a mechanism by which normal hematopoietic progenitors can survive and proliferate despite p53 expression and by which the inappropriate expression of bcl-2 and c-myc can cooperate in transformation.
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PMID:c-myc and bcl-2 modulate p53 function by altering p53 subcellular trafficking during the cell cycle. 801 82

The BCL2 gene product has been demonstrated to prevent apoptosis and provide a selective growth advantage to many cell types. We report an unexpected effect of bcl2 expression on the in vitro growth of several solid tumor cell lines. Expression of bcl2 in these cell lines resulted in growth inhibition similar to that seen with p53. In contrast, a COOH-terminal deletion mutant of bcl2 was unable to suppress growth. Thus, the bcl2 protein may exert distinct biological effects in different cell types.
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PMID:Paradoxical inhibition of solid tumor cell growth by bcl2. 803 89

Expression of the adenovirus E1A oncogene induces apoptosis which impedes both the transformation of primary rodent cells and productive adenovirus infection of human cells. Coexpression of E1A with the E1B 19,000-molecular-weight protein (19K protein) or the Bcl-2 protein, both of which have antiapoptotic activity, is necessary for efficient transformation. Induction of apoptosis by E1A in rodent cells is mediated by the p53 tumor suppressor gene, and both the E1B 19K protein and the Bcl-2 protein can overcome this p53-dependent apoptosis. The functional similarity between Bcl-2 and the E1B 19K protein suggested that they may act by similar mechanisms and that Bcl-2 may complement the requirement for E1B 19K expression during productive infection. Infection of human HeLa cells with E1B 19K loss-of-function mutant adenovirus produces apoptosis characterized by enhanced cytopathic effects (cyt phenotype) and degradation of host cell chromosomal DNA and viral DNA (deg phenotype). Failure to inhibit apoptosis results in premature host cell death, which impairs virus yield. HeLa cells express extremely low levels of p53 because of expression of human papillomavirus E6 protein. Levels of p53 were substantially increased by E1A expression during adenovirus infection. Therefore, E1A may induce apoptosis by overriding the E6-induced degradation of p53 and promoting p53 accumulation. Stable Bcl-2 overexpression in HeLa cells infected with the E1B 19K- mutant adenovirus blocked the induction of the cyt and deg phenotypes. Expression of Bcl-2 in HeLa cells also conferred resistance to apoptosis mediated by tumor necrosis factor alpha and Fas antigen, which is also an established function of the E1B 19K protein. A comparison of the amino acid sequences of Bcl-2 family members and that of the E1B 19K protein indicated that there was limited amino acid sequence homology between the central conserved domains of E1B 19K and Bcl-2. This domain of the E1B 19K protein is important in transformation and regulation of apoptosis, as determined by mutational analysis. The limited sequence homology and functional equivalency provided further evidence that the Bcl-2 and E1B 19K proteins may possess related mechanisms of action and that the E1B 19K protein may be the adenovirus equivalent of the cellular Bcl-2 protein.
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PMID:Functional complementation of the adenovirus E1B 19-kilodalton protein with Bcl-2 in the inhibition of apoptosis in infected cells. 808 92

The p53 tumor suppressor gene product is a transcriptional regulatory protein. It activates transcription from promoters that contain a p53 DNA binding site but represses many promoters that lack its binding site. High-level expression of wild-type p53 can induce apoptosis in certain cell types, and this activity can be blocked by the adenovirus E1B 19-kDa oncoprotein or by the cellular Bcl-2 oncoprotein. Here we report that p53-mediated repression of promoters that lack a p53 binding site is abrogated by the E1B 19-kDa protein or Bcl-2 oncoprotein. In contrast, transcriptional activation by p53 still occurs in the presence of either protein. The fact that two oncoproteins capable of preventing p53-mediated apoptosis also block transcriptional repression by p53 raises the possibility that p53 might induce apoptosis, at least in part, by repressing transcription.
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PMID:Relief of p53-mediated transcriptional repression by the adenovirus E1B 19-kDa protein or the cellular Bcl-2 protein. 809 Jul 49


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