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)

We have recently shown, using antisense strategy, that the RII beta regulatory subunit of cAMP-dependent protein kinase is essential for cAMP-induced growth inhibition and differentiation of HL-60 human leukemia cells. We constructed a retroviral vector for RII beta (MT-RII beta) by inserting human RII beta complementary DNA into the OT1521 retroviral vector plasmid that contains an internal mouse metallothionein-1 promoter and a neomycin resistance gene. The PA317 packaging cell line was then transfected with MT-RII beta plasmid to produce the amphotrophic stock of MT-RII beta retroviral vector. The infection with MT-RII beta and treatment with CdCl2 brought about growth arrest in HL-60 human leukemia and Ki-ras-transformed NIH 3T3 clone DT cells in monolayer culture with no sign of toxicity. The growth inhibition correlated with the expression of RII beta and accompanied changes in cell morphology; cells became flat, exhibiting enlarged cytoplasm. The growth of these cells in semisolid medium (anchorage-independent growth) was almost completely suppressed. In contrast, overexpression of the RI alpha subunit of protein kinase enhanced the cell proliferation in DT cells. The MT-RII beta-infected cells exhibited an increased sensitivity toward treatment with cAMP analogues, such as 8-Cl-cAMP and N6-benzyl-cAMP, as compared with the parental noninfected cells. In MT-RII beta HL-60 cells, N6-benzyl-cAMP treatment greatly enhanced the expression of monocytic surface markers. These results suggest that the RII beta cAMP receptor, by binding to its ligand, cAMP, acts as a tumor suppressor protein exerting growth inhibition, differentiation, and reverse transformation.
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PMID:Retroviral vector-mediated overexpression of the RII beta subunit of the cAMP-dependent protein kinase induces differentiation in human leukemia cells and reverts the transformed phenotype of mouse fibroblasts. 794 90

The ability of subtypes of retinoic acid receptors (RARs) and retinoid X receptors (RXRs) singly and in combination to elicit myeloid differentiation, G1/0-specific growth arrest, and retinoblastoma (RB) tumor suppressor protein dephosphorylation was determined in the human myeloblastic leukemia cell line HL-60 using subtype-selective retinoic acid (RA) analogs. RA analogs that selectively bind only to RARs (Am580 and/or TTNPB) or to RXRs (Ro 25-6603, SR11237, and/or SR11234) did not elicit the above-mentioned three cellular responses. In contrast, simultaneous treatment with both an RAR-selective ligand (Am580 or TTNPB) and an RXR-selective ligand (Ro 25-6603, SR11237, or SR11234) induced all three cellular processes. An RAR alpha-selective ligand used with an RXR-selective ligand generated the same responses as did all-trans RA or 9-cis RA, which affect both families of receptors, suggesting an important role for RAR alpha among RAR subtypes in eliciting cellular response. Consistent with this finding, the RAR alpha antagonist, Ro 41-5253, reduced the level of the cellular responses elicited by treatment with an RAR alpha-selective ligand plus RXR-selective ligand. The coupling of the shift of RB to its hypophosphorylated form with G1/0 arrest and differentiation in response to ligands is consistent with a possible role of RB as a downstream target or effector of RAR alpha and RXR in combination.
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PMID:Myeloid differentiation and retinoblastoma phosphorylation changes in HL-60 cells induced by retinoic acid receptor- and retinoid X receptor-selective retinoic acid analogs. 854 46

The 9ORF1 gene encodes an adenovirus E4 region oncoprotein that requires a C-terminal region for transforming activity. Screening a lambdagt11 cDNA expression library with a 9ORF1 protein probe yielded a novel cellular PDZ domain-containing protein, 9BP-1, which binds to wild-type, but not a transformation-defective, C-terminal, mutant 9ORF1 protein. The fact that PDZ domains complex with specific sequences at the free C-terminal end of some proteins led to the recognition that the 9ORF1 C-terminal region contained such a consensus-binding motif. This discovery prompted investigations into whether the 9ORF1 protein associates with additional cellular proteins having PDZ domains. It was found that the 9ORF1 protein interacts directly, in vitro and in vivo, with the PDZ domain-containing protein hDlg/SAP97 (DLG), which is a mammalian homolog of the Drosophila discs large tumor suppressor protein and which also binds the adenomatous polyposis coli tumor suppressor protein. Of interest, in forming complexes, the 9ORF1 protein preferentially associated with the second PDZ domain of DLG, similar to adenomatous polyposis coli protein. Human T cell leukemia virus type 1 Tax and most oncogenic human papillomavirus E6 oncoproteins also possessed PDZ domain-binding motifs at their C termini and, significantly, human T cell leukemia virus type 1 Tax and human papillomavirus 18 E6 proteins bound DLG in vitro. Considering the requirement of the 9ORF1 C-terminal region in transformation, these findings suggest that interactions with the cellular factor DLG may contribute to the tumorigenic potentials of several different human virus oncoproteins.
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PMID:Binding of human virus oncoproteins to hDlg/SAP97, a mammalian homolog of the Drosophila discs large tumor suppressor protein. 919 23

The RB tumor suppressor protein is a cell cycle regulator, where hypophosphorylated RB is associated with G1/0 arrest and its cyclin-dependent phosphorylation in G1 allows progression from G1 to S. The present report shows that in human leukemia cells induced to undergo growth arrest with sodium butyrate or DMSO, hypophosphorylation of the RB protein is not G1 restricted and also occurs in S and G2/M cells as well as in G1 cells when growth is inhibited. While all of the RB protein in G1/0 cells is hypophosphorylated, residual cells in S and G2 have significant detectable amounts of hypophosphorylated RB as well as still hyperphosphorylated RB protein. Thus RB hypophosphorylation can be induced in S and G2 as well as the G1 phase. The results show that growth retardation in other than the G1 phase is associated with occurrence of hypophosphorylated RB. RB may thus have a broader capability to inhibit proliferation than just in G1.
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PMID:Hypophosphorylation of the RB protein in S and G2 as well as G1 during growth arrest. 963 74

Inhibition of p53 function, through either mutation or interaction with viral or cellular transforming proteins, correlates strongly with the oncogenic potential. Only a small percentage of human T-cell lymphotropic virus type 1 (HTLV-1)-transformed cells carry p53 mutations, and mutated p53 genes have been found in only one-fourth of adult T-cell leukemia cases. In previous studies, we demonstrated that wild-type p53 is stabilized and transcriptionally inactive in HTLV-1-transformed cells. Further, the viral transcriptional activator Tax plays a role in both the stabilization and inactivation of p53 through a mechanism involving the first 52 amino acids of p53. Here we show for the first time that phosphorylation of p53 inactivates p53 by blocking its interaction with basal transcription factors. Using two-dimensional peptide mapping, we demonstrate that peptides corresponding to amino acids 1 to 19 and 387 to 393 are hyperphosphorylated in HTLV-1-transformed cells. Moreover, using antibodies specific for phosphorylated Ser15 and Ser392, we demonstrate increased phosphorylation of these amino acids. Since HTLV-1 p53 binds DNA in a sequence-specific manner but fails to interact with TFIID, we tested whether phosphorylation of the N terminus of p53 affected p53-TFIID interaction. Using biotinylated peptides, we show that phosphorylation of Ser15 alone inhibits p53-TFIID interaction. In contrast, phosphorylation at Ser15 and -37 restores TFIID binding and blocks MDM2 binding. Our studies provide evidence that HTLV-1 utilizes the posttranslational modification of p53 in vivo to inactivate function of the tumor suppressor protein.
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PMID:Phosphorylation of p53: a novel pathway for p53 inactivation in human T-cell lymphotropic virus type 1-transformed cells. 965 74

Retinoic acid (RA) activated the extracellular signal-regulated kinase (ERK) 2 mitogen-activated protein kinase (MAPK) of HL-60 human myeloblastic leukemia cells before causing myeloid differentiation and cell cycle arrest associated with hypophosphorylation of the retinoblastoma (RB) tumor suppressor protein. ERK2 activation by mitogen-activated protein/ERK kinase (MEK) was necessary for RA-induced differentiation in studies using PD98059 to block MEK phosphorylation. G0 growth arrest and RB tumor suppressor protein hypophosphorylation (which is typically associated with induced differentiation and G0 arrest), two putatively RB-regulated processes, also depended on ERK2 activation by MEK. Activation of ERK2 by RA occurred within hours and persisted until the onset of RB hypophosphorylation, differentiation, and arrest. ERK2 activation was probably needed early, because delaying the addition of PD98059 relative to that of RA restored most of the RA-induced cellular response. In contrast to RA (which activates RA receptors (RARs) and retinoid X receptors in HL-60 cells with its metabolite retinoids), a retinoid that selectively binds RAR-gamma, which is not expressed in HL-60 cells, was relatively ineffective in causing ERK2 activation. This is consistent with the need for a nuclear retinoid receptor function in RA-induced ERK2 activation. RA reduced the amount of unphosphorylated RAR-alpha, whose activation is necessary for RA-induced differentiation and arrest. This shifted the ratio of phosphorylated:unphosphorylated RAR-alpha to predominantly the phosphorylated form. Unlike other steroid thyroid hormone receptors susceptible to phosphorylation and activation by MAPKs, RAR-alpha was not phosphorylated by the activated ERK2 MAPK. The results thus show that RA augments MEK-dependent ERK2 activation that is needed for subsequent RB hypophosphorylation, cell differentiation, and G0 arrest. The process seems to be nuclear receptor dependent and an early seminal component of RA signaling causing differentiation and growth arrest.
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PMID:Retinoic acid induced mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase-dependent MAP kinase activation needed to elicit HL-60 cell differentiation and growth arrest. 967 85

Tax protein of human T-cell leukemia virus type 1 (HTLV-1) is a potent trans-activator of specific sets of target genes, and on the other hand, it is a trans-repressor of other sets of genes. It is also an inhibitor of the tumor suppressor protein p16(INK4a) and thus has been thought to contribute to induction of adult T-cell leukemia (ATL). We examined the mutagenic effects of Tax on a cellular gene, hypoxanthine guanine phosphoribosyltransferase (hprt), and LacI gene in lambda shuttle vector exogenously integrated in Big Blue Rat-2 (BBRat-2) cells. Expression of Tax in BBRat-2 cells enhanced the frequency of HPRT(-) phenotype severalfold. Tax-expressing cell clones, BBTax-1 and -2 established from BBRat-2 cells, gave rise to an average mutation frequency of 5.9 x 10(-5) in LacI gene, but Tax-negative cell clones, BBRat-C1 and -C2, showed 2. 1 x 10(-5). The 2.8-fold increase in mutation frequency in the presence of Tax indicates that Tax expression enhanced mutation frequency in chromosomal DNA. However, neither the mutation spectrum of base transitions, transversions, and deletions/insertions nor the loci of the mutations were significantly affected by Tax expression. These findings indicate that Tax has the capability to induce random mutations and suggest that Tax would be able to modulate cellular phenotypes through mutation of the cellular genome.
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PMID:Trans-activator Tax of human T-cell leukemia virus type 1 enhances mutation frequency of the cellular genome. 991 74

In HL-60 human myeloblastic leukemia cells, retinoic acid is known to cause cFMS, RAF, MEK, and ERK2 dependent myeloid cell differentiation and G0 arrest associated with RB tumor suppressor protein hypophosphorylation, implicating receptor tyrosine kinase signal transduction in propelling these retinoic acid-induced cellular effects. Furthermore, ectopic expression of polyoma middle T antigen, which activates similar early signal transduction molecules as PDGF class receptors such as cFMS, accelerates these retinoic acid-induced effects. To determine if this depends on middle T's ability to activate PLCgamma, PI-3 kinase, and src-like kinases, stable transfectants of HL-60 cells expressing either the polyoma middle T dl23 mutant, which is defective for PLCgamma and PI-3 kinase activation, or the Delta205 mutant, which in addition has greatly attenuated src-like kinase activation ability, were created and compared to wild-type middle T-transfected HL-60. The transgenes were under control of the retinoic acid (or 1, 25-dihydroxy vitamin D3) inducible Moloney murine leukemia virus LTRs. Expression of the dl23 or Delta205 mutant accelerated retinoic acid-induced cell differentiation. The effects of the mutants were comparable to those of the wild-type middle T. Likewise, retinoic acid-induced G0 arrest of mutant transfected cells and wild-type middle T transfected cells was similar. The same was true for 1, 25-dihydroxy vitamin D3-induced monocytic differentiation as for retinoic acid-induced myeloid differentiation. The mutants did not cause the same slight shortening of the cell cycle as wild-type middle T. Both the mutants and the wild-type middle T caused a similar increase in the cellular basal level of activated ERK2 MAPK. Since retinoic acid increases ERK2 activation, which is necessary for differentiation, the data suggest that mutant and wild-type middle T enhanced the retinoic acid effects by increasing basal levels of ERK2 activation. Consistent with this, the polyoma-induced foreshortening of the time for differentiation coincided with the time for retinoic acid to significantly increase ERK2 activation. As in wild-type HL-60, retinoic acid induced the early down-regulation of RXRalpha in mutant transfectants similar to wild-type middle T transfectants, consistent with no loss or gain of relevant functions due to the mutations. In contrast, vitamin D3 did not down-regulate RXRalpha in HL-60 or transfectants. Polyoma middle T and these transformation-defective mutants thus enhanced ERK2 activation to have an early effect in promoting retinoic acid-induced differentiation without a strong dependence on activating PLCgamma, PI-3 kinase, or src-like kinase.
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PMID:Transformation-defective polyoma middle T antigen mutants defective in PLCgamma, PI-3, or src kinase activation enhance ERK2 activation and promote retinoic acid-induced, cell differentiation like wild-type middle T. 1022 45

Recent evidence from several investigators suggest that the human T-cell leukemia virus type 1 Tax oncoprotein represses the transcriptional activity of the tumor suppressor protein, p53. An examination of published findings reveals serious controversy as to the mechanism(s) utilized by Tax to inhibit p53 activity and whether the same mechanism is used by Tax in adherent and suspension cells. Here, we have investigated Tax-p53 interaction simultaneously in adherent epithelial (HeLa and Saos) and suspension T-lymphocyte (Jurkat) cells. Our results indicate that Tax activity through the CREB/CREB-binding protein (CBP), but not NF-kappaB, pathway is needed to repress the transcriptional activity of p53 in all tested cell lines. However, we did find that while CBP binding by Tax is necessary, it is not sufficient for inhibiting p53 function. Based on knockout cell studies, we correlated a strong genetic requirement for the ATM, but not protein kinase-dependent DNA, protein in conferring a Tax-p53-repressive phenotype.
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PMID:Genetic evidence of a role for ATM in functional interaction between human T-cell leukemia virus type 1 Tax and p53. 1111 8

MLL (for mixed-lineage leukemia) is a proto-oncogene that is mutated in a variety of human leukemias. Its product, a homolog of Drosophila melanogaster trithorax, displays intrinsic histone methyltransferase activity and functions genetically to maintain embryonic Hox gene expression. Here we report the biochemical purification of MLL and demonstrate that it associates with a cohort of proteins shared with the yeast and human SET1 histone methyltransferase complexes, including a homolog of Ash2, another Trx-G group protein. Two other members of the novel MLL complex identified here are host cell factor 1 (HCF-1), a transcriptional coregulator, and the related HCF-2, both of which specifically interact with a conserved binding motif in the MLL(N) (p300) subunit of MLL and provide a potential mechanism for regulating its antagonistic transcriptional properties. Menin, a product of the MEN1 tumor suppressor gene, is also a component of the 1-MDa MLL complex. Abrogation of menin expression phenocopies loss of MLL and reveals a critical role for menin in the maintenance of Hox gene expression. Oncogenic mutant forms of MLL retain an ability to interact with menin but not other identified complex components. These studies link the menin tumor suppressor protein with the MLL histone methyltransferase machinery, with implications for Hox gene expression in development and leukemia pathogenesis.
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PMID:Leukemia proto-oncoprotein MLL forms a SET1-like histone methyltransferase complex with menin to regulate Hox gene expression. 1519 22


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