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 demonstrated that the gibbon ape leukemia virus (GALV) enhancer AP-1 element and the simian virus 40 AP-1 enhancer element bind different factors in HeLa nuclear extracts. A 39-kilodalton HeLa nuclear protein and the c-fos protein bind to the GALV element. Antibodies to c-fos abolish binding to the GALV AP-1 site. In contrast, anti-c-fos immunoglobulin fails to inhibit formation of the simian virus 40-specific complex from extracts of HeLa cells. Thus, AP-1-binding complexes are subject to compositional variation at different binding sites.
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PMID:Distinct factors bind the AP-1 consensus sites in gibbon ape leukemia virus and simian virus 40 enhancers. 253 54

To study the role of the protooncogene c-myb in regulating myeloid leukemia cell proliferation and differentiation, we exposed cells of the human leukemia lines HL-60, ML-3, KG-1, and KG-1a to an oligodeoxynucleotide complementary to an 18-base-pair (bp) sequence of c-myb-encoded mRNA. This treatment resulted in a significant decrease in cell proliferation in all of the lines, which was most marked in HL-60 cells. After 5 days in culture, in several separate experiments with different oligomer preparations, 75% growth inhibition was observed in c-myb antisense treated cells in comparison to untreated HL-60 cells. Two c-myb antisense oligomers of identical length with either 2- or 4-bp mismatches had no effect on cell growth nor did an 18-bp c-myb sense or myeloperoxidase antisense oligomer. The effect of a c-myc antisense oligomer (18 bp) on the growth of HL-60, KG-1, and KG-1a cells was also studied. This oligomer had much less inhibitory effect on cell proliferation than did the c-myb antisense sequence. Interestingly, although c-myc antisense treatment induced maturation of HL-60 cells while it inhibited cell proliferation, such an effect was not noted in c-myb antisense treated cells. These studies indicate that the nuclear protein encoded by the c-myb protooncogene is required for maintenance of proliferation in certain leukemia cell lines. In compared to c-myc protein suggest that, at least in HL-60 cells, c-myc amplification or N-ras activation may not be sufficient to maintain the leukemic growth in the absence of c-myb protein. These findings support the hypothesis that development and maintenance of a malignant phenotype requires a multiplicity of interrelated genetic events.
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PMID:An oligomer complementary to c-myb-encoded mRNA inhibits proliferation of human myeloid leukemia cell lines. 254 45

p53 is a nuclear protein associated with cellular transformation and normal cellular proliferation. Some transformed cells have been found to have one or several quantitative or qualitative abnormalities of p53. We studied expression, kinetics, phosphorylation, DNA methylation and chromatin structure of p53 in resting and proliferating untransformed T-lymphocytes and in human T-cell leukemia virus type I transformed T-lymphocytes from the same individuals. p53 expression is indistinguishable in transformed compared to untransformed proliferating T-lymphocytes by: (1) p53 mRNA levels, (2) rate of synthesis and stability of p53 protein, (3) change in protein stability after exposure to an inhibitor of protein synthesis, (4) presence of phosphorylation of the p53 protein. Resting T-lymphocytes from these same individuals did not express p53. No difference in DNA methylation and chromatin structure of the p53 gene was observed in either resting or proliferating untransformed, or virally transformed T-lymphocytes. The gene was fully methylated and resistant to DNAase I over its entire coding region but was demethylated and contained DNAase I hypersensitive sites in a distinct region 5' of the site of initiation of transcription.
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PMID:Expression, methylation and chromatin structure of the p53 gene in untransformed and human T-cell leukemia virus type I-transformed human T-lymphocytes. 265 79

The rex gene of the type I human T-cell leukaemia virus (HTLV-I) encodes a phosphorylated nuclear protein of relative molecular mass 27,000 which is required for viral replication. The Rex protein acts by promoting the cytoplasmic expression of the incompletely spliced viral messenger RNAs that encode the virion structural proteins. To identify the biologically important peptide domains within Rex, we introduced a series of mutations throughout its sequence. Two distinct classes of mutations lacking Rex biological activity were identified. One class corresponds to trans-dominant repressors as they inhibit the function of the wild-type Rex protein. The second class of mutants, in contrast, are recessive negative, rather than dominant negative, as they are not appropriately targeted to the cell nucleus. These results indicate the presence of at least two functionally distinct domains within the Rex protein, one involved in protein localization and a second involved in effector function. The trans-dominant Rex mutants may represent a promising new class of anti-viral agents.
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PMID:Trans-dominant inactivation of HTLV-I and HIV-1 gene expression by mutation of the HTLV-I Rex transactivator. 267 43

Human T-cell leukemia virus type I (HTLV-I) is the etiological agent of adult T-cell leukemia. The 3' end of HTLV-I proviral DNA encodes the synthesis of two regulatory proteins, tax and rex. The 40-kDa tax protein is a nuclear protein which positively stimulates transcription from the U3 region of the viral long terminal repeat sequence. Three 21-base pair sequences in the U3 region have been found to serve as the cis-element for tax-mediated trans-activation. We now report that the tax protein can trans-activate HTLV-I LTR in the absence of de novo cellular protein synthesis. Saturated mutagenesis of the 21-base pair repeat sequence showed that specific mutations clustered in sequences homologous to the cAMP responsive element (TGACGTCA) abolish trans-activation by tax. Furthermore, although the TGACGTCN element is nearly palindromic, the mutations that abolish trans-activation are localized exclusively in the 5' 6 bases, suggesting the orientation of this element may play a role in transcription. That the purified tax protein does not bind the 21-base pair repeats or nonspecific DNA lends further support to the notion that tax protein does not directly interact with the 21-base pair repeats to activate transcription. Instead, tax most likely acts via cellular transcriptional factor(s) to bring about trans-activation.
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PMID:HTLV-I tax gene product activates transcription via pre-existing cellular factors and cAMP responsive element. 276 59

Human T-cell leukemia virus type I is associated with human lymphoid malignancies. The p40xI protein encoded by the x gene of this virus is believed to play some role in virally mediated transformation. This gene is known to encode a transcriptional trans activator which previous studies have shown to be a nuclear protein. Further characterization of the intracellular kinetics of this protein showed that it migrated into the nucleus very soon after synthesis. Within the nucleus, p40xI was distributed almost equally between the nucleoplasm and the nuclear matrix. Given the proposed role of the nuclear matrix in RNA transcription, the association of p40xI with the matrix places it in an appropriate cellular compartment to exercise an effect on transcription.
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PMID:Subnuclear localization of the trans-activating protein of human T-cell leukemia virus type I. 282 64

Human pluripotential embryonic teratocarcinoma cells differentially expressed gene activity controlled by the human immunodeficiency virus type 1 (HIV-1) and human T-cell leukemia virus type I (HTLV-I) long terminal repeats (LTRs) when differentiation was induced by the morphogen all-trans retinoic acid. The alterations occurred after commitment and before the appearance of the multiple cell types characteristic of these pluripotential cells. After commitment, gene activity controlled by the HIV-1 LTR markedly increased, whereas that controlled by the HTLV-I LTR decreased. Steady-state mRNA levels and nuclear run-on transcription indicated that the increased HIV-1-directed activity during differentiation occurred posttranscriptionally, whereas the decreased HTLV-I activity was at the transcriptional level. Phorbol esters did not cause commitment but strongly enhanced expression by both viral LTRs at the transcriptional level. A specific inhibitor of protein kinase C, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, indicated that the enhanced activity involved the activation of protein kinase(s) C; altered cyclic nucleotide metabolism was apparently not involved. Differentiating cells gradually lost the ability to respond to phorbol ester stimulation. Experiments with a deletion mutant of the HIV-1 LTR suggested that this was due to imposition of negative regulation during differentiation that was not reversed by phorbol ester induction. Cycloheximide, with or without phorbol ester, slightly stimulated HIV-1-directed activity at the transcriptional level and massively increased the amounts of steady-state mRNA by posttranscriptional superinduction. It appeared, however, that new nuclear protein synthesis was required for maximal transcriptional stimulation by phorbol esters. Thus, changing cellular regulatory mechanisms influenced human retrovirus expression during human embryonic cell differentiation.
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PMID:Regulation of expression driven by human immunodeficiency virus type 1 and human T-cell leukemia virus type I long terminal repeats in pluripotential human embryonic cells. 283 1

The v-myb oncogene of avian myeloblastosis virus causes acute myelomonocytic leukemia in vivo and transforms only myeloid cells in vitro. Its product, p48v-myb, is a nuclear protein of unknown function. To determine structure-function relationships for this protein, we constructed a series of deletion mutants of v-myb, expressed them in retroviral vectors, and studied their biochemical and biological properties. We used these mutants to identify two separate domains of p48v-myb which had distinct roles in its accumulation in the cell nucleus. We showed that the viral sequences which normally encode both termini of p48v-myb were dispensible for transformation. In contrast, both copies of the highly conserved v-myb amino-terminal repeat were required for transformation. We also identified a carboxyl-terminal domain of p48v-myb which was required for the growth of v-myb-transformed myeloblasts in soft agar but not for morphological transformation.
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PMID:Structural and functional domains of the myb oncogene: requirements for nuclear transport, myeloid transformation, and colony formation. 283 3

The putative transforming protein of the type I human T-cell leukemia virus (HTLV-1) is a 40-kilodalton protein encoded by the X region and is termed p40XI. On the basis of both subcellular fractionation techniques and immunocytochemical analysis, it is now shown that p40XI is a nuclear protein with a relatively short half-life (120 minutes). It is synthesized de novo in considerable quantities in a human T-cell line infected with and transformed by the virus in vitro, and it is not packaged in detectable amounts in the extracellular virus.
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PMID:Studies of the putative transforming protein of the type I human T-cell leukemia virus. 299 27

Human T-cell leukemia viruses type I and II (HTLV-I and -II) exhibit several features characteristic of this retroviral family: the presence of an x-lor gene encoding a nuclear protein, transformation properties suggesting the involvement of a virus-associated trans-acting factor, and transcriptional trans-activation of the long terminal repeat (LTR) in infected cells. In the study described here the HTL x-lor products, in the absence of other viral proteins, were able to activate gene expression in trans directed by HTLV LTR. The regulation of the expression of particular genes in trans by HTLV x-lor products suggests that they play a role in viral replication and possibly in transformation of T lymphocytes.
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PMID:A transcriptional activator protein encoded by the x-lor region of the human T-cell leukemia virus. 299 28


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