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)

Retinoid-induced proliferation causing hyperleukocytosis is a severe complication of retinoid therapy in t(15;17) acute promyelocytic leukaemia. The molecular basis of this phenomenon is unknown. It is possible that the transiently enhanced cell proliferation results from RA-induction of growth regulatory genes. Using Differential Display of cDNAs from NB4 cells we have identified Jem, a novel gene transcript which is upregulated by retinoids during the early proliferative response in maturating cells but not in resistant cells. A 2.7 kb cDNA was cloned and sequenced. The open reading frame contains a 400 amino acid sequence corresponding to a novel 45 kDa basic protein (pI 8.9). The JEM DNA sequence is detected by FISH on human chromosome 1 at q24. The Jem peptide sequence shows a 'leucine-zipper' dimerisation motif with limited homology to Fos/Jun and ATF/CREB proteins and several putative phosphorylation sites. An atypical basic region may correspond to an unknown DNA-binding domain. The C-terminal end of Jem spans a long stretch featuring a PEST motif. After transfection into COS cells, the Jem protein shows a ponctuated nuclear localisation. We hypothesise that this novel nuclear factor may act as a transcription factor, or a coregulator, involved in either cell growth control and/or maturation.
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PMID:JEM-1, a novel gene encoding a leucine-zipper nuclear factor upregulated during retinoid-induced maturation of NB4 promyelocytic leukaemia. 912 47

Tax1, a transcriptional trans-activator of the Human T-cell leukemia virus type I (HTLV-I), induces the expression of many cellular genes through interaction with at least three distinct cellular transcription factors; CREB/ATF, NF-kappaB, and SRF. This Tax1-induced activation of cellular genes is considered to be a critical event in T-cell transformation by HTLV-I. To elucidate the role of each Tax1-inducible transcriptional pathway in T-cell transformation, we introduced Tax1 mutants with different trans-activating phenotypes into peripheral blood lymphocytes (PBL) by retroviral vectors. Analysis of these PBLs revealed that activation of the NF-kappaB pathway is sufficient to promote the growth response to IL-2. However, for the clonal expansion of CD4+ T-cells, which is a characteristic result of HTLV-I infection, activation of the CREB/ATF and SRF pathways is also required.
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PMID:Characterization of peripheral blood T-lymphocytes transduced with HTLV-I Tax mutants with different trans-activating phenotypes. 916 Aug 87

The Tax protein of the Human T-cell Leukemia Virus (HTLV) activates the expression of viral mRNA through a three 21 bp repeat enhancer located within the HTLV-1 LTR. Since Tax does not bind to the 21 bp DNA repeats directly, it has been speculated that Tax interacts with cellular protein(s) which mediate binding to the enhancer. We employed the yeast two hybrid system to identify host proteins that are potentially relevant to Tax transactivation. We identified a Tax binding protein encoded from a cDNA expression library derived from peripheral blood lymphocytes. The corresponding cDNA has sequence identity with a known transcription factor, activating factor-4 (ATF-4). ATF-4 also binds to GST-Tax fusion protein in vitro. Tax mutants that did not transactivate the HTLV-1 LTR also failed to bind ATF-4. The critical domain for Tax binding resides in a 85 amino acid stretch in the C-terminus of ATF-4, which contains the basic domain and leucine zipper. We further demonstrated that both full length and N-terminal truncated ATF-4 were able to enhance Tax transactivation. Thus, ATF-4 may act as an adapter between Tax and the TRE (Tax responsive element), and play an important role in Tax-mediated transactivation.
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PMID:Functional interaction of the HTLV-1 transactivator Tax with activating transcription factor-4 (ATF4). 919 Aug 94

Human T cell lymphotropic virus type I (HTLV-I) encodes the transactivator protein, Tax, which facilitates viral transcription from three 21 bp repeated elements within the U3 region of the long terminal repeat (LTR). Examination of the basal factors interacting with the 21 bp repeat elements through electrophoretic mobility shift (EMS) analyses has demonstrated the formation of DNA-protein complexes common to each of the 21 bp repeats (C1-C3) as well as three DNA-protein complexes specific to the promoter proximal (pp) repeat (U1 (U1A/U1B) and U2; 1-4). These studies have indicated that the individual repeats are not identical with respect to the cellular factors with which they interact. EMS analyses utilizing a series of mutated pp repeat elements demonstrate that the nucleotide sequence requirements for U1 (U1A/U1B) and U2 formation are separable from those required for C1-C3 formation. Competition EMS analyses utilizing Sp1 and CREB binding site oligonucleotides demonstrate that Sp family members are critical components of U1 (U1A/U1B) and U2 and that ATF/CREB family members are critical components of C1-C3. EMS supershift analyses have demonstrated that Sp1 is involved in U1A formation while Sp3 is involved in U1B and U2 formation. EMS analyses performed with nuclear extracts from Tax-expressing Jurkat cells and HTLV-I-transformed peripheral blood mononuclear cells demonstrate that Tax prevents the formation of U1 (U1A/U1B) and U2 DNA-protein complexes. Therefore, Tax appears to inhibit the interaction of Sp family members with the pp repeat. Based on these observations, it is possible that the interaction of Sp and ATF/CREB family members with the pp repeat during basal and Tax-mediated transcription may play a critical role in viral gene expression during the initial stages of virus infection or during activation of a latent infection.
Leukemia 1997 Apr
PMID:Sp family members preferentially interact with the promoter proximal repeat within the HTLV-I enhancer. 920 81

Characterization of the cellular transcription factors interacting with the human T cell lymphotropic virus type I (HTLV-I) long terminal repeat (LTR) is essential to dissecting the mechanisms involved in viral transcription that may be pertinent to the oncogenic and neuropathogenic processes associated with HTLV-I infection in both the immune and nervous systems. Electrophoretic mobility shift (EMS) analyses utilizing oligonucleotides homologous to each of the 21 bp repeat elements reacted with nuclear extracts derived from cell lines of lymphocytic, monocytic, neuronal, and glial cell origin have demonstrated differential binding of cellular factors to the three 21 bp repeats (1-4). ATF/CREB and Sp family members interacted with the 21 bp repeats to form DNA-protein complexes common to all cell types examined. However, a unique DNA-protein complex was detected when the promoter central 21 bp repeat was reacted with nuclear extracts derived from either the U-373 MG glioblastoma cell line or the THP-1 mature monocytic cell line. Based on nucleotide sequence requirements and immunoreactivity, we demonstrate that this DNA-protein complex is comprised of the AP-1 components, Fos and Jun.
Leukemia 1997 Apr
PMID:AP-1 derived from mature monocytes and astrocytes preferentially interacts with the HTLV-I promoter central 21 bp repeat. 920 84

A mutational analysis of human T-cell leukemia virus type 2 (HTLV-2) Tax (Tax-2) was performed to identify regions within Tax-2 important for activation of promoters through the CREB/ATF or NF-kappaB/Rel signaling pathway. Tax-2 mutations within the putative zinc-binding region as well as mutations at the carboxy terminus disrupted CREB/ATF transactivation. A single mutation within the central proline-rich region of Tax-2 disrupted the transactivation of the NF-kappaB/Rel pathway. Surprisingly, this mutation, which is thought to be in a separate activation domain, was suppressed by mutations within or around the putative zinc-binding region, suggesting an interaction between these two regions. These analyses indicate that the functional regions or domains important for transactivation through the CREB/ATF or NF-kappaB/Rel signaling pathway are similar, but not identical, in Tax-1 and Tax-2. Identification of these distinct Tax-2 mutants should facilitate comparative biological studies of HTLV-1 and HTLV-2 and ultimately lead to the determination of the functional importance of Tax trans-acting capacities in T-lymphocyte transformation by HTLV.
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PMID:Mutational analysis of human T-cell leukemia virus type 2 Tax. 934 58

The human T-cell leukemia virus type 1 Tax protein transforms human T lymphocytes, which can lead to the development of adult T-cell leukemia. Tax transformation is related to its ability to activate gene expression via the ATF/CREB and the NF-kappaB pathways. Transcriptional activation of these pathways is mediated by the actions of the related coactivators CREB binding protein (CBP) and p300. In this study, immunocytochemistry and confocal microscopy were used to localize CBP and p300 in cells expressing wild-type Tax or Tax mutants that are able to selectively activate gene expression from either the NF-kappaB or ATF/CREB pathway. Wild-type Tax colocalized with both CBP and p300 in nuclear bodies which also contained ATF-1 and the RelA subunit of NF-kappaB. However, a Tax mutant that selectively activates gene expression from only the ATF/CREB pathway colocalized with CBP but not p300, while a Tax mutant that selectively activates gene expression from only the NF-kappaB pathway colocalized with p300 but not CBP. In vitro and in vivo protein interaction studies indicated that the integrity of two independent domains of Tax delineated by these mutants was involved in the direct interaction of Tax with either CBP or p300. These studies are consistent with a model in which activation of either the NF-kappaB or the ATF/CREB pathway by specific Tax mutants is mediated by distinct interactions with related coactivator proteins.
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PMID:Differential transcriptional activation by human T-cell leukemia virus type 1 Tax mutants is mediated by distinct interactions with CREB binding protein and p300. 952 8

The human T-cell leukemia virus type I (HTLV-I) is a causative agent of adult T-cell leukemia. Although the exact mechanism by which HTLV-I contributes to leukemogenesis is still unclear, the Tax protein is thought to play a major role in this process. This 40-kDa polypeptide is able to interact with the tumor suppressor p16(INK4A). Consequently, Tax can activate the signaling pathway that lead to the release of E2F that in turn induces expression of factors required for cell cycle progression. In this paper, we demonstrate that Tax can also activate E2F-mediated transcription independently of p16(INK4A). Indeed, when Tax is coexpressed with the E2F-1 transcription factor in CEM T-cells, which lack expression of p16(INK4A), it strongly potentiates the E2F-dependent activation of a reporter construct driven by a promoter containing E2F binding sites. This stimulation is abrogated by mutations affecting the E2F-binding sites. In addition, Tax also stimulates the transcription of the E2F-1 gene itself. Using Tax mutants that fail to activate either ATF- or NF-kappaB-dependent promoters and different 5' truncation mutants of the E2F-1 promoter, we show that the Tax-dependent transcriptional control of the E2F1 gene involves, at least in part, the ATF binding site located in the E2F-1 promoter.
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PMID:Activation of E2F-mediated transcription by human T-cell leukemia virus type I Tax protein in a p16(INK4A)-negative T-cell line. 972

The Tax protein of the human T-cell leukemia virus type 1 (HTLV-1) has been implicated in human T-cell immortalization. The primary function of Tax is to transcriptionally activate the HTLV-1 promoter, but Tax is also known to stimulate expression of cellular genes. It has been reported to associate with several transcription factors, as well as proteins not involved in transcription. To better characterize potential cellular targets of Tax present in infected cells, a Saccharomyces cerevisiae two-hybrid screening was performed with a cDNA library constructed from the HTLV-1-infected MT2 cell line. From this study, we found 158 positive clones representing seven different cDNAs. We focused our attention on the cDNA encoding the transcription factor CREB-2. CREB-2 is an unconventional member of the ATF/CREB family in that it lacks a protein kinase A (PKA) phosphorylation site and has been reported to negatively regulate transcription from the cyclic AMP response element of the human enkephalin promoter. In this study, we demonstrate that CREB-2 cooperates with Tax to enhance viral transcription and that its basic-leucine zipper C-terminal domain is required for both in vitro and in vivo interactions with Tax. Our results confirm that the activation of the HTLV-1 promoter through Tax and factors of the ATF/CREB family is PKA independent.
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PMID:CREB-2, a cellular CRE-dependent transcription repressor, functions in association with Tax as an activator of the human T-cell leukemia virus type 1 promoter. 973 79

The proto-oncogene Fli-1, a member of Ets family is rearranged or activated through proviral integration in erythroleukemias, induced by Friends' Murine Leukemia Virus. The DNA binding domain (ETS domain) of Fli-1 is fused to the RNA binding domain of EWS by t(11q24:22q12) chromosomal translocation in Ewing's sarcoma and primitive neuroectodermal tumors. Screening of human cDNA libraries has identified two different 5'-termini and alternatively spliced forms of the human Fli-1 gene (Fli-1b), suggesting the possible existence of two independent promoters. The genomic sequence adjacent to the alternate exon of human Fli-1b gene shows functional promoter activity when cloned in promoter-less CAT expression vector and transfected into QT-6 cells. The transcription initiation (CAP) site and minimum promoter region necessary for function were localized. The 5'-flanking regions of human Fli-1b and mouse Fli-1 show 80% homology suggesting conserved promoter regulatory elements. The Fli-1b 5'-flanking sequence lacks canonical TATA or CCAAT boxes but contains a partially conserved TATA-like sequence at position 242. Several transcription factor binding sequences like ATF/CREB, E2A-PBX1, EBP, PEA-3, ETS-2, Sp-1, c-Myc, TBP, GATA-1 and Oct-3 were conserved in the promoter sequence. Functional promoter assays revealed that Fli-1b promoter shows very strong transcriptional activation compared to Fli-1 promoter. We also showed that variant Fli-1b has transcriptional activation properties similar to those of Fli-1. Fli-1b and Fli-1 show differential expression in various hematopoietic cell lines. This differential expression and promoter activities of Fli-1 and Fli-1b suggests that several mechanisms are involved in Fli-1 gene regulation which are mediated by many transcription factors.
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PMID:Fli-1b is generated by usage of differential splicing and alternative promoter. 976 25


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