Abundant transcription of a cellular gene in T cells infected with human T-cell leukemia-lymphoma virus

From differential display to DNA microarrays--a personal account

This article is a tribute to Dr. Arthur Pardee, one of the most innovative and brilliant scientists of our time, on the occasion of his 85th birthday. In this partially perspective and partially review piece, I look back how fate, by twist and turn, has led me eventually to his lab at Harvard where we worked out the Differential Display technology from scratch, how the method has revolutionized the field of gene expression analysis and where DD is taking us in the "era" of DNA microarrays.

Effect of human T-cell leukemia virus type I tax protein on activation of the human vimentin gene

We report that the expression of the vimentin gene, a cytoskeletal growth-regulated gene, is activated in trans by the Tax (p40x) transactivator protein encoded by the human T-cell leukemia virus type I. Expression of the Tax protein activates a number of cellular genes, such as those coding for the alpha chain of the high-affinity interleukin-2 receptor and interleukin-2. These findings indicate that the Tax protein is involved in the unregulated T-cell growth associated with human T-cell leukemia virus type I infection. Higher levels of vimentin mRNA were expressed in two human T-cell leukemia virus type I-transformed T cell lines, C91/PL and C81-66/45, when compared with that in Jurkat T cells. We demonstrate that this activation is conferred by the vimentin upstream flanking sequences. Indeed, enhanced activity was detected when constructs with the vimentin promoter linked to the chloramphenicol acetyltransferase gene were transfected in HeLa cells and in two cell lines of hematopoietic origin (Jurkat T lymphoblastoid cells and U937 promonocytic cells) together with a Tax expression plasmid. By introducing a series of deletions in the vimentin promoter, we further restrict these sequences to 30 base pairs, located between 241 and 210 base pairs upstream of the mRNA cap site. A 40-base-pair oligonucleotide containing this regulatory region proved sufficient to confer Tax inducibility upon a heterologous promoter linked to chloramphenicol acetyltransferase. Importantly, this segment includes an 11-base-pair promoter segment that has homology with the binding site for the NF-kappa B transactivating factor. Our findings indicate that constitutive expression of the vimentin gene under the control of the Tax protein may be relevant in understanding the progression of the lymphoproliferative process associated with human T-cell leukemia virus type I infection.

Stable expression of a selectable myeloproliferative sarcoma virus in murine T lymphocyte and monocyte cell lines

We have investigated whether a retroviral vector based on the myeloproliferative sarcoma virus (MPSV) can be expressed in murine T cells and macrophages. This vector (neoR MPSV) carries the dominant selection marker for neomycin resistance (neoR) and the mos oncogene. The murine T cell line BW5147 and the monocytic cell line P388D1 were either transfected with neoR MPSV DNA or infected with neoR MPSV virus. From both lines, neoR cell clones could be established by retroviral infection, but not by calcium-phosphate precipitation-mediated DNA transfection. The efficiency of infection could be increased 60- to 200-fold upon cocultivation of target cells with irradiated neoR MPSV virus-producing cells. All neoR clones showed neoR MPSV specific sequences as revealed by dot blot and Southern blot analysis. The integration and expression of neoR MPSV was stable over a period of now more than 4 months, even in the absence of selection for neomycin resistance. Northern blot analysis showed that neoR clones express full length neoR MPSV. Further, clones of both T cell and monocyte origin were capable to produce infectious virus particles as revealed by focus formation on fibroblasts and conversion of neomycin sensitive fibroblasts to a neomycin resistant phenotype.

IL-2- and IL-2-R- independent proliferation of T-cell lines from adult T-cell leukemia/lymphoma patients

Human T-cell leukemia/lymphoma virus I (HTLV-I) is known to be associated with adult T-cell leukemia/lymphoma (ATL) as an etiological agent. The mechanism of leukemogenesis by HTLV, however, is still obscure. Two hypotheses have been proposed concerning abnormalities in IL-2 production and its receptor (Tac antigen) expression based on the experimental observations of IL-2-dependent ATL cell lines. In this study, we examine these hypotheses by using 3 leukemic T-cell lines from 3 Japanese patients with ATL. These cell lines were cultivated and established without addition of IL-2 to the culture medium. Cell-surface phenotype analysis by immunofluorescence with monoclonal antibodies (MAbs) and IL-2 binding assays revealed that one of the ATL cell lines, HPB-ATL-2, expresses only a minimal amount of IL-2 receptor (IL-2-R) on the cell surface and binds less radiolabelled human recombinant IL-2 than the other highly Tac-positive cell lines. Expression of Tac antigen in all ATL cell lines was not affected by IL-2, anti-Tac MAb or the tumor-promoter phorbol ester in the culture medium. The culture supernatant from these cell lines showed no IL-2 activity toward Con-A-stimulated human peripheral blood lymphocytes, and their growth was not affected by additional IL-2 in cultures. IL-2-independent growth and constitutive expression of its receptors on the cell surface were evident in our ATL cell lines. However, dense expression of IL-2 receptors was not essential for stimulation of leukemic proliferation of T cells by HTLV-I. Trans-activation of the PX40 gene product of HTLV-I for activation of IL-2-R gene might not be coincidentally associated with stimulation for cell proliferation.

Location of cis-acting regulatory sequences in the human T-cell leukemia virus type I long terminal repeat

The location of cis-acting regulatory regions within the long terminal repeat (LTR) of the human T-cell leukemia virus type I (HTLV-1) was determined. The sequences present between nucleotides -350 and -55 (cap site +1) contain an enhancer element that is active in lymphoid and nonlymphoid cell lines. The sequences located near the "TATA" and RNA initiation sites contain a promoter, the activity of which can be augmented by homologous and heterologous enhancer elements. A region responsive to trans-acting transcription factors present in HTLV-I- and HTLV type II-infected cells is located between nucleotides -159 and +315. HTLV-I LTR deletion mutants respond in a similar manner both to the trans-acting factors present in infected cells and to the tat protein encoded by the x-lor region of the genome, thus providing further evidence that the tat protein mediates transcriptional trans-activation of the LTR in HTLV-infected cells.

Growth-related changes in specific mRNAs upon lectin activation of human lymphocytes

A cDNA library in lambda gt10 was constructed from the cytoplasmic poly(A) +RNA of human peripheral blood lymphocytes after 72 hr of phytohemagglutinin stimulation, with the aim of assessing selective gene expression as a result of lymphocyte activation. Thirteen recombinants were isolated by the use of an enriched probe and differential screening. These clones were categorized into two groups with respect to their hybridization to mRNA. In the first group three recombinants were isolated, which hybridized to single discrete mRNAs in the size range 0.7-1.7 kb. The mRNAs corresponding to these clones were present at elevated levels in activated lymphocytes, but the kinetics of increase differed. The 0.7-kb mRNA coded for by clone p1L1 increased two-fold at 6 hr and remained elevated over 72 hr, as did beta-actin mRNA. The 1.7-kb mRNA coded for by clone p9L2 increased two- to three-fold after 6 hr and was maximally expressed after 24 hr exposure to phytohemagglutinin, coincident with the onset of DNA replication, and maintained this level up to 72 hr. The 1.0-kb mRNA coded by p10L2F which was rare in resting cells increased 25- to 30-fold after 6 hr, prior to overall transcriptional increases and reached peak levels after 72 hr when a substantial proportion of the cells were in the S and G2 + M phases of the cell cycle. This clone was undetectable or very rare in the leukemic T-lymphoblast cell line CCRF-CEM. The second group of clones, consisting of the remaining 10 recombinants, did not hybridize to discrete bands, but to a smear on RNA blots.(ABSTRACT TRUNCATED AT 250 WORDS)

A microassay for detection of DNA and RNA in small numbers of plant cells

A microtechnique for the detection of DNA or RNA in small numbers of plant cells (1-50) has been developed using cauliflower mosaic virus (CaMV) infection of turnip as a model system. Both DNA and RNA extracted from 10 mesophyll protoplasts from CaMV-infected plants can be detected by hybridization using a radioactive probe made from cloned CaMV DNA (pCaMV10). No hybridization above background was detected in extracts of protoplasts from uninfected plants. At least 0.15 pg (11 000 molecules) of purified pCaMV10 DNA can be detected. This method is superior to existing 'macro' techniques for nucleic acid detection as smaller amounts of tissue are required and the detection is approximately 100-fold more sensitive. re]19850326 rv]19850530 ac]19850611.

Analysis of gene expression during hematopoiesis: present and future applications

Recombinant DNA technology now provides the strategies required to identify genes whose expression controls the development of normal and pathologic blood cells. Characterization of the gene families responsible for synthesis of hemoglobins, immunoglobulins, histocompatibility antigens, and cellular enzymes have already, or are about to, provide major insights into the mechanisms producing normal erythroid cells, immunocytes, and immune surface features. Hemoglobinopathies, leukemias, and autoimmune diseases of the bone marrow can now be examined to a degree of detail previously inaccessible to investigators. Oncogene translocation analysis is shedding new light on the pathogenesis of leukemias and lymphomas. Recent basic advances now permit direct cloning and identification of genes in host organisms which express their protein products, thus allowing isolation of genes coding for the hematopoietic surface markers and growth factors which characterize and regulate blood cell progenitors. This review summarizes the molecular genetic approach to analysis of normal and pathologic hematopoiesis, surveys major findings which have resulted, and examines the potential use of refined gene cloning strategies for improved understanding of blood cell development.

Cyclosporin A inhibits T-cell growth factor gene expression at the level of mRNA transcription

Cyclosporin A (CsA) is a potent immunosuppressive agent, now gaining wide application in human organ transplantation. The immunosuppressive activity of CsA is at least in part due to inhibition of lymphokine production by activated T lymphocytes. Specifically, inhibition of T-cell growth factor (TCGF; also designated interleukin 2) production appears to be an important pathway by which CsA impairs T-cell function. To define further both the specificity of CsA and the level at which it interferes with lymphokine gene expression, we have studied its effects on TCGF mRNA accumulation as well as TCGF gene transcription. These studies were performed with a cloned human leukemic T-cell line (Jurkat, subclone 32), which can be induced with phytohemagglutinin and phorbol 12-myristate 13-acetate to produce large amounts of TCGF. In these cells, high levels of TCGF mRNA were present in induced but not in uninduced Jurkat cells as judged by hybridization to a cloned human TCGF cDNA probe. CsA completely inhibited induced TCGF mRNA accumulation at concentrations of 0.3-1.0 microgram/ml, whereas low levels of appropriately sized TCGF mRNA were present at 0.01 microgram/ml. In nuclear transcription experiments, CsA inhibited the synthesis of TCGF transcripts in a dose-dependent manner with complete inhibition at a concentration of 1 microgram/ml. In contrast, CsA did not inhibit the expression of two other inducible genes, TCGF receptor and HT-3. Further, HLA gene expression was also less affected than TCGF in CsA-treated cells. These data suggest a relatively selective action of CsA on TCGF gene transcription.

DNA methylation and expression of HLA-DR alpha

B-cell lines established from two individuals with T-cell acute lymphocytic leukemia (T-ALL) express HLA-DR antigens, whereas the isogenic T-cells do not. The lack of expression correlates with a lack of detectable HLA-DR mRNA. All of the DR alpha DNA sequences detected by a cloned DR alpha cDNA probe are contained in a BglII fragment which varies slightly in size (4.0 to 4.8 kilobases) from one individual to another. In DNA from the T-cells not expressing DR alpha mRNA, all of the potential HpaII sites within the BglII fragment appeared to be methylated. In contrast, at least some of these sites were not methylated in DNA from the B-cells expressing high levels of DR alpha mRNA. Treatment of these T-cells with 5-azacytidine resulted in the induction of DR surface antigen expression, the appearance of DR alpha mRNA, and the partial demethylation of the DR alpha DNA sequences. T-cell lines established from human T-cell leukemia-lymphoma virus associated T-cell neoplasias, in contrast to the T-cell acute lymphocytic leukemia cell lines, expressed both DR antigens and DR alpha mRNA; the HpaII sites within the BglII fragment of DR alpha DNA of these human T-cell leukemia-lymphoma virus-positive T-cell lines were in all cases at least partially unmethylated. Uncultured peripheral blood T-cells from human T-cell leukemia-lymphoma virus-infected individuals expressed DR antigens at a low level, and the DR alpha locus was partially unmethylated. After 48 h in culture, DR antigen expression was substantially increased, but no significant changes were observed in methylation of the DR alpha locus or in the amount of DR mRNA which was present. This suggests that expression of DR antigens also can be modulated post-transcriptionally.

DNA methylation and expression of HLA-DR alpha

B-cell lines established from two individuals with T-cell acute lymphocytic leukemia (T-ALL) express HLA-DR antigens, whereas the isogenic T-cells do not. The lack of expression correlates with a lack of detectable HLA-DR mRNA. All of the DR alpha DNA sequences detected by a cloned DR alpha cDNA probe are contained in a BglII fragment which varies slightly in size (4.0 to 4.8 kilobases) from one individual to another. In DNA from the T-cells not expressing DR alpha mRNA, all of the potential HpaII sites within the BglII fragment appeared to be methylated. In contrast, at least some of these sites were not methylated in DNA from the B-cells expressing high levels of DR alpha mRNA. Treatment of these T-cells with 5-azacytidine resulted in the induction of DR surface antigen expression, the appearance of DR alpha mRNA, and the partial demethylation of the DR alpha DNA sequences. T-cell lines established from human T-cell leukemia-lymphoma virus associated T-cell neoplasias, in contrast to the T-cell acute lymphocytic leukemia cell lines, expressed both DR antigens and DR alpha mRNA; the HpaII sites within the BglII fragment of DR alpha DNA of these human T-cell leukemia-lymphoma virus-positive T-cell lines were in all cases at least partially unmethylated. Uncultured peripheral blood T-cells from human T-cell leukemia-lymphoma virus-infected individuals expressed DR antigens at a low level, and the DR alpha locus was partially unmethylated. After 48 h in culture, DR antigen expression was substantially increased, but no significant changes were observed in methylation of the DR alpha locus or in the amount of DR mRNA which was present. This suggests that expression of DR antigens also can be modulated post-transcriptionally.

Oncogenes: clues to carcinogenesis

Recent applications of recombinant DNA techniques in cancer research led to the detection of cellular genes with potential transforming activity, called oncogenes (c-onc). Regularly they seem to be involved in normal cell differentiation and proliferation: a number of oncogene-encoded proteins specifically phosphorylates tyrosine, a key reaction in growth control. Certain human tumors exhibit activated forms of these genes and DNA fragments isolated from these neoplasms transform nonneoplastic cells (transfection assay). Oncogenes were first discovered and defined in a number of retroviruses; these viral oncogenes (v-onc) are thought to have been derived from the cellular oncogenes (c-onc). By integration of the v-onc genes into the host genome acute neoplastic transformation of the cell may occur. Several modes of oncogene activation are discussed that lead either to an increased dosage of gene product or to the formation of an altered gene product. The localization of oncogenes in the human genome near the breakpoints of specific chromosome aberrations involved in various neoplasms like Burkitt lymphoma and several leukemias emphasizes the importance of these genes in carcinogenesis.

Retrovirus transfer of a bacterial gene into mouse haematopoietic progenitor cells

The haematopoietic system is made up of a hierarchy of cells with different developmental, functional and proliferative capacities. Although cellular diversity appears to arise from the commitment and maturation of stem cells, the molecular basis for this differentiation process is unknown. The introduction of cloned DNA sequences into haematopoietic progenitor cells would provide a novel approach for studying this differentiating in vivo system. One laboratory has reported DNA-mediated transfer of genes into mouse bone marrow cells. However, retroviruses offer a number of advantages over DNA-mediated gene transfer procedures, including high efficiency infection of a wide range of cell types in vitro and in vivo, stable and low copy integration into the host chromosome, and a defined integrated provirus structure. For these reasons recombinant DNA techniques have been utilized to construct high efficiency retrovirus vectors expressing foreign genes. We demonstrate here, using such a retrovirus vector, the transfer of a dominant selectable drug-resistance gene into defined classes of mouse haematopoietic progenitor cells. These observations should facilitate the development of molecular genetic approaches to fundamental and clinical problems in haematopoiesis.

Transformation of human umbilical cord blood T cells by human T-cell leukemia/lymphoma virus

Several isolates of human T-cell leukemia/lymphoma virus (HTLV) were transmitted to normal human T cells obtained from the umbilical cord blood of newborns. T cells from seven specimens were immortalized by infection with different HTLV isolates and their properties were compared with those of activated uninfected normal T cells grown in the presence of T-cell growth factor (TCGF) and with those of HTLV-positive neoplastic T-cell lines derived from patients with T-cell malignancies. The HTLV-infected cells generally belonged to a class of mature T cells (OKT4+ and Leu 3A+) and differed from the normal uninfected cells in that they could be propagated in culture indefinitely; possessed altered morphology, including convoluted nuclei and some bi- and multinucleated giant cells; formed large clumps in culture; demonstrated a diminished requirement for TCGF; had an increased density of TCGF receptors; often became completely independent of exogenous TCGF; and expressed HLA-DR determinants. These properties of the HTLV-infected cord blood T cells contrasted to those of uncultured cord blood T cells and of cord blood cells stimulated with mitogen and grown with TCGF but resembled the characteristics of T-cell lines established previously from patients with HTLV-associated T-cell malignancies. This in vitro system offers a unique opportunity to study the basic mechanism involved in abnormal growth and neoplastic transformation of a specific class of human T cells.

A survey of human leukaemias for sequences of a human retrovirus

Human T-cell leukaemia-lymphoma virus (HTLV) is an exogenous human retrovirus distinct from all known animal retroviruses. HTLV is closely linked to a subtype of adult T-cell malignancies and except for isolated cases, has not been found associated with any other form of leukaemia, lymphoma or other cancers (see refs 1, 2 for review). HTLV can be transmitted to cord blood T lymphocytes in vitro and the infected cells exhibit characteristics of transformed neoplastic T cells. We have recently cloned DNA sequences derived from approximately 1 kilobase (kb) of the 5' and 3' termini of the HTLV genome, as well as a 4-5-kb defective HTLV provirus flanked by cellular sequences. The availability of these probes has enabled us to carry out a limited survey of different fresh or cultured cells from patients of different lymphoid and myeloid malignancies for HTLV-related DNA sequences. The results presented here show that cells from all Japanese patients with adult T-cell leukaemia and several patients with various mature T-cell malignancies from elsewhere contained one or more copies of a highly conserved HTLV genome. The infected cells are of clonal origin. Fresh cells from 1 of the 10 myeloid leukaemic patients contained exogenous DNA sequences distantly related to HTLV.