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)

Cooperation between the adenovirus E1A and E1B oncogenes is required for transformation of primary quiescent rodent cells. Although expression of E1A alone will stimulate cell proliferation sufficient to initiate transformed focus formation, proliferation fails to be sustained and foci degenerate. Coexpression of either the 19-kDa or 55-kDa E1B oncoproteins with E1A permits high-frequency transformation by overcoming this cytotoxic response. Without E1B 19-kDa protein expression, however, transformants remain susceptible to induction of cell death. Rapid loss of viability is coincident with nucleolytic cleavage of DNA in intranucleosomal regions and chromatin condensation, hallmarks of programmed cell death (apoptosis). Furthermore, overexpression of a known suppressor of apoptosis, the Bcl-2 protooncogene, can rescue E1A-induced focus degeneration. Thus E1A-dependent stimulation of cell proliferation is accompanied by apoptosis and thereby insufficient to singly induce transformation. High-frequency transformation requires a second function encoded by the E1B 19-kDa protein to block apoptosis.
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PMID:The adenovirus E1A proteins induce apoptosis, which is inhibited by the E1B 19-kDa and Bcl-2 proteins. 145 5

The survival-promoting activity of the Bcl-2 family of proteins appears to be modulated by interactions between various cellular proteins. We have identified a novel cellular protein, Bik, that interacts with the cellular survival-promoting proteins, Bcl-2 and Bcl-xL, as well as the viral survival-promoting proteins, Epstein Barr virus-BHRF1 and adenovirus E1B-19 kDa. In transient transfection assays, Bik promotes cell death in a manner similar to the death-promoting members of the Bcl-2 family, Bax and Bak. This death-promoting activity of Bik can be suppressed by coexpression of Bcl-2, Bcl-XL, EBV-BHRF1 and E1B-19 kDa proteins suggesting that Bik may be a common target for both cellular and viral anti-apoptotic proteins. While Bik does not show overt homology to the BH1 and BH2 conserved domains characteristic of the Bcl-2 family, it does share a 9 amino acid domain (BH3) with Bax and Bak which may be a critical determinant for the death-promoting activity of these proteins.
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PMID:Bik, a novel death-inducing protein shares a distinct sequence motif with Bcl-2 family proteins and interacts with viral and cellular survival-promoting proteins. 747 23

Hygromycin B, an aminoglycoside antibiotic that is widely used to establish stable mammalian cell lines that carry a bacterial gene conferring resistance to the drug, is shown here to induce apoptotic programmed cell death in susceptible cells. Dying cells exhibited typical features of apoptosis, including cell shrinkage, membrane blebbing, nuclear pyknosis, and extensive internucleosomal fragmentation of DNA. Employing concentrations of hygromycin B that are typically used for selecting stable cell lines, we show that susceptible cells die rapidly, exhibiting the morphological properties of apoptosis by 18 h and detectable DNA fragmentation as early as 2 h after receiving the drug. G418, on the other hand, required days to cause cell death, which was not accompanied by internucleosomal DNA fragmentation. Apoptotic cell killing by hygromycin B did not require expression of wild-type p53 and was suppressed by both Bcl-2 and the Adenovirus type 5 E1B 19-kDa protein.
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PMID:Induction of p53-independent apoptosis by hygromycin B: suppression by Bcl-2 and adenovirus E1B 19-kDa protein. 758 55

Overexpression of Bcl-2 can prevent or markedly delay cell death induced by a variety of apoptotic stimuli. Although Fas and Fas ligand (FasL) interactions play a major role in the elimination of self-reactive T cells in the periphery, inhibition of Fas-mediated killing by Bcl-2 has not been consistently observed. The mouse T hybridoma 2B4.11 (2B4) has been a useful model to study glucocorticoid- and activation-induced apoptosis, which is mediated through Fas and FasL. Using both stable transfectants and transient transfections, overexpression of Bcl-2 or Bcl-xL readily blocked glucocorticoid-induced but not activation-induced apoptosis of 2B4 cells. Bcl-2 expression did not inhibit Fas-mediated cytotoxicity triggered by cells expressing FasL or by the transient transfection of human Fas. Similarly, overexpression of Bcl-2 in the mouse T hybridoma A1.1 did not block activation-induced/Fas-mediated apoptosis. In Jurkat cells, however, expression of Bcl-2 partially inhibited anti-Fas-induced cell death. A Bcl-2-related protein that can interfere with anti-Fas killing, the adenoviral E1B 19K, also did not block activation-induced/Fas-mediated apoptosis in 2B4 cells. In contrast, expression of CrmA, a cowpox virus protein that inhibits ICE-like protease activity, blocked activation-induced apoptosis in 2B4 cells but had little effect on Dex-mediated cytotoxicity. These results show that: 1) Bcl-2 can have strikingly different anti-cell death activity in the same cell depending upon the apoptotic stimulus, 2) distinct apoptosis signaling pathways may exist with differential sensitivity to Bcl-2 and ICE-like protease inhibitors.
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PMID:Bcl-2 blocks glucocorticoid- but not Fas- or activation-induced apoptosis in a T cell hybridoma. 759 63

The adenovirus E1A oncogene products stimulate DNA synthesis and cell proliferation but fail to transform primary baby rat kidney (BRK) cells because of the induction of p53-mediated programmed cell death (apoptosis). Overexpression of dominant mutant p53 (to abrogate wild-type p53 function) or introduction of apoptosis inhibitors, such as adenovirus E1B 19K or Bcl-2 oncoproteins, prevents E1A-induced apoptosis and permits transformation of BRK cells. The ability of activated Harvey-ras (H-ras) to cooperate with E1A to transform BRK cells suggests that H-ras is capable of overcoming the E1A-induced, p53-dependent apoptosis. We demonstrate here that activated H-ras was capable of suppressing apoptosis induced by E1A and wild-type p53. However, unlike Bcl-2 and the E1B 19K proteins, which completely block apoptosis but not p53-dependent growth arrest, H-ras expression permitted DNA synthesis and cell proliferation in the presence of high levels of wild-type p53. The mechanism by which H-ras regulates apoptosis and cell cycle progression is thereby strikingly different from that of the E1B 19K and Bcl-2 proteins. BRK cells transformed with H-ras and the temperature sensitive murine mutant p53(val 135), which lack E1A, underwent growth arrest at the permissive temperature for wild-type p53. p53-dependent growth arrest, however, could be relieved by E1A expression. Thus, H-ras alone was insufficient and cooperation of H-ras and E1A was required to override growth suppression by p53. Our data further suggest that two complementary growth signals from E1A plus H-ras can rescue cell death and thus permit transformation.
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PMID:Activated H-ras rescues E1A-induced apoptosis and cooperates with E1A to overcome p53-dependent growth arrest. 762 44

E1A of human adenovirus type 5 (Ad5) encodes proteins of 289 and 243 residues (289R and 243R) which differ only by the 46 amino acid CR3 region known to activate expression of certain cellular and early viral genes. E1A proteins also induce DNA synthesis and cell transformation, but as well can stimulate apoptosis. Two adenovirus E1B products act to protect cells from E1A-induced cell death, including a 19 kDa protein which is functionally similar to the cellular Bcl-2 suppressor of apoptosis, and a 55 kDa species which binds to and inhibits p53. Previous studies suggested that E1A-induced cell death occurs via a p53-dependent mechanism requiring regions of E1A proteins linked to induction of DNA synthesis and cell transformation. We report here that the 289R E1A protein induces apoptosis in cell lines lacking p53, whereas the 243R product was dependent upon p53. We also show that this p53-independent process involves the expression of one or more additional viral proteins which are presumably synthesized in response to transactivation by 289R. Thus E1A proteins induce cell death by both p53-dependent and p53-independent mechanisms involving separate E1A functions.
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PMID:Adenovirus E1A proteins induce apoptosis by both p53-dependent and p53-independent mechanisms. 763 Jun 30

A number of DNA viruses carry apoptosis-inhibiting genes which enable the virus to escape from the host response. The adenovirus E1B 19K protein can inhibit apoptosis induced by E1A, tumour-necrosis factor-alpha, FAS antigen and nerve growth factor deprivation. The molecular basis of this inhibition remains poorly understood, but the fact that protection is seen in the absence of other viral proteins suggests that E1B 19K targets cellular proteins. We report here the identification of three cellular proteins that bind E1B 19K. One of these is a new member of the bcl-2 family, which we have called bak (for bcl-2 homologous antagonist/killer). This protein, which is expressed in a wide variety of cell types, binds to E1B 19K and to the Bcl-2 homologue Bcl-XL (ref. 17) in yeast. In addition, overexpression of bak in sympathetic neurons deprived of nerve growth factor accelerates apoptosis and blocks the protective effect of co-injected E1B 19K.
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PMID:Cloning of a bcl-2 homologue by interaction with adenovirus E1B 19K. 771 29

Adenovirus E1B 19K protein prevents premature death of adenovirus-infected cells. Viral mutants (19K mutants) defective in the 19K protein induce enhanced cell death, resulting in fragmentation of viral and cellular DNA. The 19K protein can also suppress the effects of certain external cell death-inducing stimuli, such as tumor necrosis factor alpha and various DNA-damaging agents that induce apoptosis. We have examined viral infection of permissive human cells and nonpermissive rat cells to determine if the 19K mutant induces apoptotic or necrotic type of cell death. Infection of normal rat kidney cells with an adenovirus type 2 19K deletion mutant induces internucleosomal DNA fragmentation and condensation of nuclear chromatin. Electron microscopic examination of these cells revealed the presence of condensed subnuclear bodies characteristic of apoptosis. In contrast, infection of human A549 cells induces random DNA fragmentation, and these cells do not exhibit characteristic condensation of the nuclear chromatin but contain enlarged nuclei loaded with virus particles. Therefore, it appears that adenovirus infection induces both apoptotic and necrotic types of cell death, depending on the cell type. Both types of cell death can be suppressed by E1B 19K protein. Similarly, a recombinant adenovirus expressing the human Bcl-2 protein but lacking the E1B proteins can efficiently suppress both apoptotic and necrotic cell death induced by adenovirus infection. The requirement of p53 tumor suppressor protein in adenovirus-induced cell death was investigated by infection of human Saos2 and mouse p53 nullizygous (p53-/-) cells lacking p53 tumor suppressor protein.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:p53-independent apoptotic and necrotic cell deaths induced by adenovirus infection: suppression by E1B 19K and Bcl-2 proteins. 775 71

Adenovirus E1B 19 kDa protein protects against cell death induced by viral infection and certain external stimuli. The Bcl-2 protein can functionally substitute for the E1B 19 kDa protein. To identify cellular targets for the 19 kDa protein, we used the two-hybrid screen in yeast. We have isolated cDNAs for three different proteins, designated Nip1, Nip2, and Nip3, that interact with the 19 kDa protein. Mutational analysis indicates that these proteins do not associate with 19 kDa mutants defective in suppression of cell death, suggesting a correlation between interaction of these proteins and suppression of cell death. These proteins also associate with discrete sequence motifs in the Bcl-2 protein that are homologous to motifs of the 19 kDa protein. Our results suggest that two diverse proteins, the E1B 19 kDa and the Bcl-2 proteins, promote cell survival through interaction with a common set of cellular proteins.
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PMID:Adenovirus E1B 19 kDa and Bcl-2 proteins interact with a common set of cellular proteins. 800 Nov 38

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


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