Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Genes, pX”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed1995

Ribozyme-mediated RNA degradation in nuclei suspension.

Ribozymes containing 2'-fluoro- and 2'-amino-modified pyrimidine nucleosides in combination with terminal phosphorothioate linkages were targeted against HTLV-I tax RNA. In order to examine the activity of such chemically modified ribozymes in the nuclear environment, they were incubated with nuclei of a Tax-transformed mouse fibroblast cell line. Ribozyme cleavage of tax RNA was analyzed by the RNase protection assay. Comparison of the cleavage of tax RNA isolated nuclei with that of tax RNA present in nuclei suspension revealed a 30 times more efficient cleavage of the latter one. Pre-treatment with proteinase K and SDS abolished the enhancement of the ribozyme-mediated RNA cleavage. Catalytically inactive ribozymes did not yield any cleavage products. These results demonstrate an augmenting effect of nuclear proteins on the ribozyme-mediated RNA cleavage.

Animals↗
PubMed1995

Quantification of HTLV-II proviral copies by competitive polymerase chain reaction in peripheral blood mononuclear cells of Italian injecting drug users, central Africans, and Amerindians.

To better correlate the burden of human T cell leukemia virus type I (HTLV-I) and type II (HTLV-II) infection with diagnostic and prognostic markers, we developed a new competitive polymerase chain reaction (PCR) assay for the quantitative determination of proviral copy numbers in infected cells. A competitive plasmid was constructed that carried a 112-bp fragment from a highly conserved region of the HTLV tax gene and that was further modified by inserting a sequence of 24 bp. This competitive PCR assay system can be used for the quantification of HTLV-I and HTLV-II proviral DNA as demonstrated by using HTLV-I- and HTLV-II-infected cell lines and/or patient material. We determined the HTLV-II proviral load in peripheral blood mononuclear cells (PBMCs) of 11 Italian injecting drug users (IDUs) infected by this virus and in PBMCs of 10 seropositive Amerindian and Central African individuals from endemically infected ethnic groups. A great variation was observed in the number of HTLV-II proviral sequences in the PBMCs of Italian drug abusers, ranging from 5-10 to 16,239 copies/10(5) cells. There was no clear-cut correlation between proviral load, CD8 count, stage of HIV-1 infection, and therapy. A considerable variation in HTLV-II proviral load was also observed in PBMCs of Amerindians and Central Africans with no correlation between the amount of HTLV-II provirus and the geographic origin of the infected individuals.

Adolescent↗
PubMed1996

Insights on the pathogenicity of human T-lymphotropic/leukemia virus types I and II.

Human T-lymphotropic/leukemia virus types I and II (HTLV-I and HTLV-II) are phylogenetically and immunologically related viruses that differ in their pathogenicity in vivo. HTLV-I is the etiologic agent of adult T-cell leukemia/lymphoma, as well as a chronic progressive myelopathy, HTLV-I-associated myelopathy/tropical spastic paraparesis. In contrast, HTLV-II has not been conclusively associated with specific diseases. Both HTLV-I and HTLV-II transform CD4+ T-cells in vitro, but their in vivo target cells appear to differ. HTLV-I is found mainly in CD4+ cells, whereas HTLV-II has been demonstrated mainly in CD8+ cells. Clearly the definition of the viral genetic determinants responsible for the different tropism and pathogenicity in vivo may provide the basis of our understanding of the HTLV-I oncogenicity. In this short review we emphasize two aspects of viral infection of T cells: (1) the influence of viral infection on the major proteins involved in the G0-G1 phase of the cell cycle and (2) the effect of viral infection on the S phase of the cell cycle, i.e., the interleukin-2 receptor pathway.

Alternative Splicing↗
PubMed1996

Coding potential of the X region of human T-cell leukemia/lymphotropic virus type II.

Human T-cell leukemia/lymphotropic viruses type I and type II (HTLV-I and HTLV-II) are complex human retroviruses showing a similar genetic organization but substantially different biologic and pathogenic properties. As in other complex retroviruses, the 3' portion of the HTLV genome contains the peculiar "X region" comprising several partially overlapping open reading frames (ORFs). To search for a possible basis for the pathogenic differences between the two viruses, a number of studies have been carried out to analyze the coding potential of the X region of HTLV-I and, more recently, of HTLV-II. This review focuses on the coding potential of the HTLV-II X region and presents a comparison with that of HTLV-I. Expression of different ORFs present in the X region may be accessed through two expression strategies: alternative splicing and translation of more than one protein from the same mRNA. Initial analyses of the X region proteins indicate that some differ significantly from their HTLV-I homologues, thus providing possible clues to the understanding of the complex life cycle and pathogenicity of the two viruses.

Alternative Splicing↗
PubMed1996

The difficulty of detecting HTLV-1 proviral sequences in patients with mycosis fungoides.

Although most patients with cutaneous T cell lymphomas, including mycosis fungoides (MF) and its leukemic variant, the Sézary syndrome, are seronegative for antibodies to the human T cell lymphotropic viruses (HTLV-I/II), it has recently been shown that > 95% of such patients harbor proviral DNA sequences related to the region of the HTLV genome that encodes the transregulatory/transforming gene, tax. However, the demonstration of HTLV sequences, even after amplification by polymerase chain reaction (PCR), has not been universally successful, and some investigators continue to question this observation. In an effort to resolve this controversy, we have compared published methodologies that have been less successful with techniques currently used in this laboratory. Major differences were found in (a) the nature of the cells used [freshly isolated versus cultured peripheral blood mononuclear cells (PBMC)] and (b) the methods used to prepare samples for PCR (whole cell lysates versus DNA extracts). PBMC from 10 different MF patients and the healthy daughter of 1 of the patients were subjected to comparative analyses. While all of the PBMC lysates were positive, the DNA extract from only one of these individuals revealed HTLV tax sequences. Studies were also conducted comparing cell lysates and DNA extracts of cultured cells derived from tax sequence-positive PBMC from seven different MF patients. The cells from four of the seven were shown to have retained tax sequences after varying times in culture, when whole-cell lysates were used as targets for PCR amplification and Southern analysis, whereas none of the DNA extracts were positive. It appears that the use of whole-cell lysates instead of DNA extracts and the use of fresh instead of cultured cells greatly enhance the ability to detect HTLV-1 tax sequences in specimens from MF patients.

Blotting, Southern↗
PubMed1998

HTLV-I and HTLV-II virus expression increase with HIV-1 coinfection.

Coinfections with HIV-1 and HTLV-I or HTLV-II have been associated with unique immunophenotypes and an increased risk for development of neurodegenerative conditions. These findings may result from an increased HTLV-I or II viral burden in dually infected individuals. To investigate this possibility, HTLV-I/II tax/rex messenger RNA and viral antigen expression in peripheral blood mononuclear cells (PBMCs) were measured in 37 HTLV-I- or HTLV-II-infected subjects with or without HIV-1 coinfection. Tax/rex messenger RNA was detected in 14 of 24 PBMC samples from dually infected subjects, compared with only 1 of 13 PBMC samples from singly infected subjects (58% versus 7%; p < .003). The reverse transcription-polymerase chain reaction (RT-PCR) assay correlated with HTLV-I/II viral antigen detection in PBMC cultures but not with HIV-1 viral load levels in plasma. These findings may provide clues regarding the pathophysiologic consequences of HIV/HTLV-I and HIV/HTLV-II coinfections.

Antigens, Viral↗
PubMed2003

Human T-cell lymphotropic virus type I (HTLV-I)-related clinical and laboratory findings for HTLV-I-infected blood donors.

Clinical and laboratory findings were examined for 111 human T-cell lymphotropic virus type I (HTLV-I)-infected blood donors. HTLV-I provirus loads in subjects with a family history of adult T-cell leukemia (ATL) or HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) tended to be higher than those in subjects without a family history of these conditions. There were 3 asymptomatic patients with ATL, 4 with a history of uveitis, 7 with hyperreflexia in the lower limbs, and 3 with urinary frequency in the night. The mean CD4 cell/CD8 cell ratio +/- SD was significantly lower (p<.0001) in subjects with hyperreflexia in the lower limbs (1.3 +/- 0.2) than in subjects without any clinical abnormalities (1.7 +/- 0.6), suggesting that subjects with hyperreflexia in the lower limbs already have some immunologic abnormalities. The concordance of HTLV-I infection between husband and wife was lower in this study than in a previous study. HTLV-I-related inflammatory symptoms were more frequent (p =.021, Fisher exact test; OR = 9.5; 95% CI, 1.7-53.5) in HTLV-I tax A-infected donors (3 [50%] of 6 donors) than in HTLV-I tax B-infected donors (10 [9.5%] of 105 donors), suggesting different risks of HTLV-I-related symptoms according to the virus genotype.

Adult↗
PubMed1993

Complete sequence conservation of the human T cell leukaemia virus type 1 tax gene within a family cluster showing different pathologies.

We have amplified, through PCR, the full-length tax gene of human T cell leukaemia virus type 1 (HTLV-1) derived from proviral DNA of peripheral blood lymphocytes of five first degree relatives of Afro-Caribbean origin. One patient (the father) had adult T cell leukaemia (ATL), one (the mother) tropical spastic paraparesis (TSP), and three (children) were healthy asymptomatic carriers. All five family members had identical tax nucleotide sequences as determined by direct sequencing of PCR products. This sequence was compared with tax gene sequences of an unrelated TSP patient of Afro-Caribbean origin, and of C8166 cells, and found to have one and seven nucleotide differences, respectively. At the amino acid level these three sequences differed from the HTLV-1 prototype Japanese strain (ATK-1). All sequence changes were clustered towards the 3' end of the gene. These data demonstrate the complete conservation of an HTLV-1 gene following, presumably, horizontal and vertical transmission of the virus. Clones of this gene showed more sequence variation within the TSP patient than the ATL patient, mostly consisting of point mutations; there was no conservation of mutations between the two individuals. These mutations occurred only in individual clones of the ATL patient whereas those of the TSP patient were found to be repeated in different clones. A tax-specific cytotoxic T lymphocyte response was observed in two asymptomatic carriers with low antibody titres, whereas none was detected in an individual with a high antibody level. No tax-specific sequence was identified which may have contributed to the apparently high degree of transmission from mother to children (three of five children tested) nor account for the differences between disease symptoms in the parents.

Adult↗
PubMed1994

Calcium-mediated inhibition of phorbol ester and Tax trans-activation of the human T cell leukaemia virus type 1.

Human Jurkat T cells containing a stably integrated human T cell leukaemia virus type 1 (HTLV-1) long terminal repeat (LTR) reporter gene construct were used to study the role of calcium-dependent cellular activation pathways in LTR trans-activation. Treatment of these cells with the calcium ionophore ionomycin resulted in a reduced basal response of the LTR and reduced responses to 12-O-tetradecanoylphorbol-13-acetate-and Tax-mediated trans-activation. This effect was also observed for virus production in the HTLV-1-producing T cell line MT-2. Experiments designed to determine the events underlying this inhibition, using inhibitors of calcium-related events, revealed that the ionomycin-induced repression of the LTR was alleviated in all cases by cyclosporin A. This compound was also effective in preventing the ionomycin-induced reduction in virus production in MT-2 cells. These results suggest a role for calcium-related events in the down-regulation of HTLV-1 expression.

Calcium↗
PubMed1996

The presence of a divergent T-lymphotropic virus in a wild-caught pygmy chimpanzee (Pan paniscus) supports an African origin for the human T-lymphotropic/simian T-lymphotropic group of viruses.

We isolated a divergent simian T-lymphotropic virus (STLV) (strain PP1664) from a wild-caught African bonobo (pygmy chimpanzee, Pan paniscus). Molecular and phylogenetic characterization of this virus show that it reliably separates from the two well-established primate T-lymphotropic virus types, HTLV-I/STLV-I (PTLV-I) and PTLV-II, and from a third type isolated from an African-born Papio hamadryas and designated by us as PTLV-L. Four of eight bonobos kept at the Antwerp Zoo, Belgium, showed an aberrant PTLV serology. We amplified and sequenced a 709 bp PTLV proviral tax/rex fragment from one of the reactive bonobos. It differs by about 25 % from the homologous nucleotide sequences of PTLV-I and PTLV-L and by about 17 % from PTLV-II. This is comparable to the differences among the three known types. Including the most divergent STLV-I strains sequenced to date, for example, strain PHSu1 sequenced here, the divergence in this region within PTLV-I is less than 11 % and within PTLV-II less than 4%. Although very divergent, this new bonobo STLV is the closest well-characterized simian relative of HTLV-II, raising the possibility of very divergent new HTLV strains. Our results show that the number of PTLV types should be considered open and that the variety of indigenous viruses in the PTLV group is greatest in Africa. Thus, as for the other primate retroviruses HIV and SIV, PTLV most probably has its origins in Africa.

Africa↗
PubMed2000

Virus inactivation in a proportion of human T-cell leukaemia virus type I-infected T-cell clones arises through naturally occurring mutations.

Human T-cell leukaemia virus type I (HTLV-I) is the aetiological agent of adult T-cell leukaemia/lymphoma and tropical spastic paraparesis/HTLV-I-associated myelopathy (TSP/HAM). The trans-activating protein (Tax) of HTLV-I is strongly implicated in cellular proliferation. We examined the tax gene and 5' long terminal repeat (LTR) sequences in eight naturally infected T-cell clones derived from TSP/HAM-affected individuals who were either productively (proliferate spontaneously) or silently (do not proliferate spontaneously) infected. In two silently infected clones point mutations within the proviruses resulted in truncation of the Tax protein. One clone harboured both a deleterious tax gene mutation and a point mutation in an enhancer element of the 5' LTR. Sequence changes, immunological escape mutation, integration site context and host cell phenotype may all contribute to the high proportion of latently or silently infected T-cells found in vivo in virus carriers.

5' Untranslated Regions↗
PubMed1990

Identification of HTLV-I tax trans-activator mutants exhibiting novel transcriptional phenotypes.

The type I human T-cell leukemia virus (HTLV-I) encodes a 40-kD nuclear trans-regulatory protein termed Tax that transcriptionally activates the HTLV-I long terminal repeat (LTR), as well as select [corrected] cellular and heterologous viral promoters. Tax does not bind DNA specifically but, rather, acts in a more indirect manner. Tax activation of the HTLV-I LTR is mediated through constitutively expressed cellular factors that bind to cAMP response elements (CREs) present within the 21-bp enhancers of the LTR. In contrast, Tax transactivation of the interleukin-2 receptor-alpha gene (IL-2R alpha) and LTR of the type 1 human immunodeficiency virus (HIV-1) involves the induced nuclear expression of NF-kappa B. We now report the identification of missense mutations within the tax gene that functionally segregate these two pathways of trans-activation. Additionally, we demonstrate that the carboxyl terminus of the Tax protein, despite its acidic and predicted alpha-helical structure, is completely dispensable for trans-activation through either of these transcription factor pathways. Finally, we demonstrate that mutations within a putative zinc finger domain disrupt the nuclear localization of Tax and abolish trans-activation. These results demonstrate that Tax trans-activation of viral and cellular promoters involves at least two mechanisms of host transcription factor activation and suggest that this activation is likely mediated through distinct functional domains.

Amino Acid Sequence↗
PubMed1992

The Rex system of bacteriophage lambda: tolerance and altruistic cell death.

The rexA and rexB genes of bacteriophage lambda encode a two-component system that aborts lytic growth of bacterial viruses. Rex exclusion is characterized by termination of macromolecular synthesis, loss of active transport, the hydrolysis of ATP, and cell death. By analogy to colicins E1 and K, these results can be explained by depolarization of the cytoplasmic membrane. We have fractionated cells to determine the intracellular location of the RexB protein and made RexB-alkaline phosphatase fusions to analyze its membrane topology. The RexB protein appears to be a polytopic transmembrane protein. We suggest that RexB proteins form ion channels that, in response to lytic growth of bacteriophages, depolarize the cytoplasmic membrane. The Rex system requires a mechanism to prevent lambda itself from being excluded during lytic growth. We have determined that overexpression of RexB in lambda lysogens prevents the exclusion of both T4 rII mutants and lambda ren mutants. We suspect that overexpression of RexB is the basis for preventing self-exclusion following the induction of a lambda lysogen and that RexB overexpression is accomplished through transcriptional regulation.

Adenosine Triphosphate↗
PubMed1996

Localization of human T-cell lymphotropic virus-1 tax proviral sequences in skin biopsies of patients with mycosis fungoides by in situ polymerase chain reaction.

The histopathologic diagnosis of mycosis fungoides (MF), even when clinical manifestations of the disease seem convincing, is often tenuous. The observation that practically all patients with MF harbor human T cell lymphotropic virus type I (HTLV-I) proviral sequences in their circulating lymphocytes raised the possibility that such viral footprints could be detected in their cutaneous infiltrates. Application of in situ polymerase chain reaction (PCR) to skin biopsies of 11 of 12 patients demonstrated this assumption to be correct. In addition, cells suspected to be keratinocytes were also positive. None of 10 skin biopsies from a variety of sources used as controls, nor 3 lymph node biopsies from patients with B-cell lymphomas, showed any HTLV proviral sequences on in situ PCR. On the basis of these observations, it is concluded that in situ PCR carried out on skin biopsies of patients with presumptive MF may help to established the diagnosis.

Genes, pX↗
PubMed1999

Efficient propagation of human herpesvirus 6B in a T-cell line derived from a patient with adult T-cell leukemia/lymphoma.

The efficient propagation of the OK strain of the B variant of human herpesvirus 6 (HHV-6B) was demonstrated in a line of T cells, TaY, established from the peripheral blood lymphocytes of a patient with adult T-cell leukemia/lymphoma (ATL). Growth of TaY cells depends on the presence of IL-2 and the cells harbor HTLV-I genomes. A severe cytopathic effect (CPE) was observed in many HHV-6B(OK)-infected TaY cells one week after infection. The release of virus from HHV-6B(OK)-infected TaY cells [TaY(OK)] was first detected after three days and increased rapidly for up to seven days after infection, as demonstrated by PCR. The titer of HHV-6B(OK) in the supernatant was comparable to the value of 10(3.5) TCID50/ml obtained with PHA-activated cord blood lymphocytes (CBL) that had been infected with HHV-6B(OK). The replication of the virus was shown to depend to a considerable extent on cell viability. Electron microscopy revealed many herpesvirus-type capsid- and enveloped-viruses in the nuclei and cytoplasm of degenerated cells in TaY(OK) cultures. The U1102 strain of HHV-6A and the Z29 strain of HHV-6B also infected TaY cells productively, as detected by PCR and an immunofluorescence test. These results suggest that the activation of CD4+ T lymphocytes with mitogens such as PHA or IL-2 and the expression of some cellular gene or the HTLV-I gene might be essential for efficient propagation of HHV-6B. TaY cells should play an important role in future investigations of cell-virus interactions and genetic variations or cell tropism of HHV-6 isolates since no cell line that shows propagation of both HHV-6A and HHV-6B has been reported to date.

Antigens, CD↗
PubMed2001

Growth inhibition of cancer cells by co-transfection of diphtheria toxin A-chain gene plasmid with bovine leukemia virus-tax expression vector.

We constructed a plasmid containing bovine leukemia virus (BLV)-tax gene driven by SR alpha promoter, designated as pME-BLVtax, to activate the promoter of the long terminal repeat (LTR) of BLV in various tumor cells. Activation of the promoter of BLV-LTR by pME-BLVtax was confirmed by luciferase assay. When the cells, such as COS-1, C8, and KU-1, were transfected with a plasmid pBLV-LUC1, which contained the luciferase gene under the control of BLV-LTR, and pME-BLVtax, luciferase was expressed in these cells, whereas no luciferase gene expression was observed when only pBLV-LUC1 was introduced into the cells. Activation of the BLV-LTR promoter was regulated by pME-BLVtax and 0.5 microg of pME-BLVtax was sufficient for the expression of the gene under the control of BLV-LTR. Furthermore, pME-BLVtax was used to direct the cell expression of the gene for diphtheria toxin A-chain under the control of BLV-LTR (pLTR-DT) to various tumor cell lines, KU-1, C8, COS-1, BL2M3, and HeLa cells. The transfection was carried out with cationic liposomes. In this experiment, co-transfection of pLTR-DT with pME-BLVtax exerted selective growth inhibitory effects on the tumor cell lines. Moreover, three co-introductions of pLTR-DT with pME-BLVtax into the cell lines resulted in significant inhibition of the cell growth. This result suggests that the delivery of the pLTR-DT and pME-BLVtax genes into tumor cells by the use of cationic liposomes may be potentially useful as a novel approach for the treatment of tumor cells.

Animals↗
PubMed1993

Aberrant expression of the p53 tumor suppressor gene in adult T-cell leukemia and HTLV-I-infected cells.

By immunoprecipitation analysis, enhanced p53 expression was detected in 3 of 4 adult T-cell leukemia (ATL) cell lines, 1 of 3 HTLV-I-infected cell lines and 1 of 5 fresh ATL samples, compared with phytohemagglutinin-stimulated peripheral blood lymphocytes. Among these 5 high expressers, p53 missense mutations were indicated in 2 ATL cell lines and 1 fresh ATL sample by extensive p53 cDNA and genomic DNA polymerase chain reaction single-strand conformation polymorphism analysis. No mutation was found throughout the entire coding region of the remaining 2 high expressers (1 ATL and 1 HTLV-I-infected cell lines) and low expressers of p53 (2 HTLV-I-infected cell lines). Tax oncoprotein expression was found in these 2 high p53 expressers in which p53 mutation was not present, but not in low p53 expressers or cells carrying this mutation. The levels of p53 mRNA were similar among the samples regardless of p53 levels. Posttranscriptional mechanisms other than missense mutation would thus appear to increase p53 in the Tax-expressing cells but not in cells containing undetectable levels of Tax. No complex formation between p53 and Tax was observed.

Adult↗
PubMed2005

Sensitivity of adult T-cell leukaemia lymphoma cells to tumour necrosis factor-related apoptosis-inducing ligand.

Tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) induces apoptosis in many transformed cells, but not in normal cells, and hence TRAIL has recently emerged as a novel anti-cancer agent. Adult T-cell leukaemia lymphoma (ATLL) is a neoplasm of T-lymphocyte origin aetiologically associated with human T-lymphotropic virus type 1 (HTLV-I), and is resistant to standard anti-cancer therapy. We thus characterized the sensitivity of ATLL cells to TRAIL in this study. Although most primary ATLL cells and cell lines expressed TRAIL death receptors on their surface, they showed only restricted sensitivity to TRAIL. Among the 10 ATLL cell lines examined, one was sensitive, but two had insufficient death-receptor expression, two had an unknown resistant mechanism with abrogation of the death signal upstream of caspase-8, and the remaining five showed attenuation of the signal in both extrinsic and intrinsic pathways by X-linked inhibitor of apoptosis and Bcl-2/Bcl-xL respectively. Furthermore, the level of HTLV-I tax expression was significantly correlated to TRAIL resistance. Interestingly, ATLL cells themselves expressed TRAIL on the cell surface. Constitutive production of TRAIL may offer resistance, thus allowing the development of TRAIL-resistant ATLL cells. Consequently, the resistant mechanism in ATLL cells against TRAIL was assigned to multiple factors and was not explained by a definitive single agent.

Antineoplastic Agents↗