The human IL-2 receptor gene contains a positive regulatory element that functions in cultured cells and cell-free extracts

Overexpression of interleukin 2 receptor, thymidine kinase and immunoglobulin-associated alpha-1 messenger RNA in a clinical case of enzootic bovine leukosis

A 49-month-old Holstein cow with anorexia, tachypnea, enlarged peripheral lymph nodes, and difficulty standing up was suspected of bovine leukosis. Hematological examination revealed lymphocytosis with the presence of neoplastic cells. Increased total lactate dehydrogenase (LDH) activity, isozymes of LDH-2 and LDH-3 activities and thymidine kinase activity were observed. Cytological findings of fine needle aspiration of subiliac lymph nodes indicated lymphosarcoma. Histopathology and antibody analysis confirmed the diagnosis of enzootic bovine leukosis, a B-cell bovine lymphoma caused by bovine leukemia virus. Gene expressions known as biomarkers of hematopoietic neoplasia in human were also examined in the present case. Increased messenger RNA expression of interleukin 2 receptor, thymidine kinase, and immunoglobulin-associated alpha-1 was observed in the case animal.

Dichotomy of all-trans retinoic acid inducing signals for adult T-cell leukemia

We previously reported that all-trans retinoic acid (ATRA) inhibits growth in human T-cell leukemia virus type 1 (HTLV-1)-positive T-cell lines and fresh cells from patients with adult T-cell leukemia. However, the mechanism of this inhibition is not clear. In the present study, we observed that NF-kappaB transcriptional activity as well as cell growth decreased significantly in HTLV-1-positive T-cell lines in the presence of ATRA. Furthermore, we observed that ATRA reduced HTLV-1 proviral DNA, HTLV-1 genes (gag, tax, or pol mRNA) using the real-time quantitative polymerase chain reaction. SIL-2R was reduced by ATRA in both protein level (culture supernantant) and mRNA level in HTLV-1-positive T-cell lines. Interestingly, ATRA significantly inhibited RT activity similar to azidothimidine (AZT) in HTLV-1-positive T-cell lines. Moreover, AZT inhibited proviral DNA but not NF-kappaB transcriptional activity, and sIL-2R on HTLV-1; however, ATRA inhibited of NF-kappaB, proviral DNA and sIL-2R on HTLV-1. These results suggested that the decrease in sIL-2R induced by ATRA may be caused by the actions of a NF-kappaB inhibitor acting on the NF-kappaB/sIL-2R signal pathway. These results suggested that ATRA could have two roles, as a NF-kappaB inhibitor and as an RT inhibitor.

Cloning and chromosomal assignment of the porcine interleukin-2 receptor alpha (IL-2Ralpha) gene

Porcine genomic DNA encoding a 55 kDa subunit of interleukin-2 receptor (IL-2R), which is termed alpha chain (IL-2Ralpha), was cloned by repeated plaque hybridization using IL-2Ralpha cDNA as a probe. Two different lambda phage clones, one of which encoded exon 1 and the 5'-upstream flanking region of IL-2Ralpha gene and another encoded the sequence from exon 2 to exon 8, were isolated. By analysis of the 5'-upstream region of the gene, putative binding motifs for transcription factors such as GATA family proteins, Ikaros, NF-kappaB, NF-IL2Ralpha and SRF, were found as described in human, murine and bovine genes. Two additional motifs for STAT4 binding were also found in this region. Moreover, using the FISH technique, we assigned the porcine IL-2Ralpha locus to the distal end of the long arm of chromosome 10 (10q6-qter) where the vimentin gene had been assigned nearby.

Elf-1 contributes to the function of the complex interleukin (IL)-2-responsive enhancer in the mouse IL-2 receptor alpha gene

Lymphocytes regulate their responsiveness to IL-2 through the transcriptional control of the IL-2R alpha gene, which encodes a component of the high affinity IL-2 receptor. In the mouse IL-2R alpha gene this control is exerted via two regulatable elements, a promoter proximal region, and an IL-2-responsive enhancer (IL-2rE) 1.3 kb upstream. In vitro and in vivo functional analysis of the IL-2rE in the rodent thymic lymphoma-derived, CD4- CD8- cell line PC60 demonstrated that three separate elements, sites I, II, and III, were necessary for IL-2 responsiveness; these three sites demonstrate functional cooperation. Site III contains a consensus binding motif for members of the Ets family of transcription factors. Here we demonstrate that Elf-1, an Ets-like protein, binds to site III and participates in IL-2 responsiveness. In vitro site III forms a complex with a protein constitutively present in nuclear extracts from PC60 cells as well as from normal CD4- CD8- thymocytes. We have identified this molecule as Elf-1 according to a number of criteria. The complex possesses an identical electrophoretic mobility to that formed by recombinant Elf-1 protein and is super-shifted by anti-Elf-1 antibodies. Biotinylated IL-2rE probes precipitate Elf-1 from PC60 extracts provided site III is intact and both recombinant and PC60-derived proteins bind with the same relative affinities to different mutants of site III. In addition, by introducing mutations into the core of the site III Ets-like motif and comparing the corresponding effects on the in vitro binding of Elf-1 and the in vivo IL-2rE activity, we provide strong evidence that Elf-1 is directly involved in IL-2 responsiveness. The nature of the functional cooperativity observed between Elf-1 and the factors binding sites I and II remains unresolved; experiments presented here however suggest that this effect may not require direct interactions between the proteins binding these three elements.

Mouse interleukin-2 receptor alpha gene expression. Interleukin-1 and interleukin-2 control transcription via distinct cis-acting elements

We have shown that interleukin-1 (IL-1) and IL-2 control IL-2 receptor alpha (IL-2R alpha) gene transcription in CD4-CD8- murine T lymphocyte precursors. Here we map the cis-acting elements that mediate interleukin responsiveness of the mouse IL-2R alpha gene using a thymic lymphoma-derived hybridoma (PC60). The transcriptional response of the IL-2R alpha gene to stimulation by IL-1 + IL-2 is biphasic. IL-1 induces a rapid, protein synthesis-independent appearance of IL-2R alpha mRNA that is blocked by inhibitors of NF-kappa B activation. It also primes cells to become IL-2 responsive and thereby prepares the second phase, in which IL-2 induces a 100-fold further increase in IL-2R alpha transcripts. Transient transfection experiments show that several elements in the promoter-proximal region of the IL-2R alpha gene contribute to IL-1 responsiveness, most importantly an NF-kappa B site conserved in the human and mouse gene. IL-2 responsiveness, on the other hand, depends on a 78-nucleotide segment 1.3 kilobases upstream of the major transcription start site. This segment functions as an IL-2-inducible enhancer and lies within a region that becomes DNase I hypersensitive in normal T cells in which IL-2R alpha expression has been induced. IL-2 responsiveness requires three distinct elements within the enhancer. Two of these are potential binding sites for STAT proteins.

Contrasting effect of transforming growth factor type beta 1 (TGF-beta 1) on proliferation and interleukin-2 receptor expression in activated and rapidly cycling immature (CD3-CD4-CD8-) thymocytes

Transforming growth factor beta (TGF-beta) is a cytokine with immunoregulatory properties that acts negatively on T lymphocyte proliferation. However, with the EL 4-6.1 variant of the murine thymoma EL 4 activated with phorbol ester and/or interleukin-1 (IL-1), we recently found that it up-regulates interleukin-2-receptor (IL-2R) expression. Since EL 4-6.1 cells share phenotypic and functional characteristics with the immature thymic subset lacking CD4 and CD8 accessory molecules (DN), we investigated the effect of TGF-beta 1 on the IL-2R 55kD alpha chain expression and proliferation of activated DN cells and especially in DN cells that do not express CD3. We observed that TGF-beta 1 was able to increase both the percentage of CD3-DN cells expressing IL-2R alpha chains and the expression of IL-2R alpha chain in these cells. This stimulatory effect of TGF-beta 1 was distal from early transduction events. In addition, TGF-beta 1 was found to modulate CD3-DN cell proliferation. During differentiation in the thymus, CD3-DN cells transiently express the IL-2R alpha chain of the IL-2R and these IL-2R+ CD3-DN cells are preprogrammed to down-regulate the IL-2R alpha chain and up-regulate the CD4 and CD8 accessory molecule. We thus also tested the effect of TGF-beta 1 on IL-2R alpha chain expression in these in vitro differentiating CD3-DN cells. We found that TGF-beta 1 neither significantly affected IL-2R expression nor changed CD4 or CD8 expression. Hence, in CD3-DN cells, the effect of TGF-beta 1 on IL-2R expression seems to be restricted to proliferating cells.

Transforming growth factor type beta 1 (TGF-beta 1) down-regulates interleukin-2 production and up-regulates interleukin-2 receptor expression in a thymoma cell line

Transforming growth factor type beta 1 (TGB-beta 1) belongs to a family of polypeptides with regulatory effects on growth and differentiation of a variety of cell types. TGB-beta 1 plays an important role in regulation of immune response by acting as a negative control signal for T cell proliferation through still unknown mechanisms. In this study we have analysed the effects of TGB-beta 1 on EL 4-6.1, a variant of the murine EL 4 thymoma, which can be induced by phorbol 12-myristate 13-acetate (PMA) and/or interleukin 1 (IL-1) to secrete interleukin 2 (IL-2) and express IL-2 receptors (IL-2R). Using this defined model system, we show that TGB-beta 1 simultaneously down-regulates IL-2 expression and up-regulates the number of both high and low affinity IL-2R. These changes correlate with changes at the mRNA level, suggesting an effect at the pre-translational level. The specificity of both TGF-beta 1 effects was demonstrated using a neutralizing antiserum to TGF-beta 1. Our data also suggest that TGF-beta 1 does not interfere with early activation signals of PMA and/or IL-1. This model might be useful for elucidating the complex role of TGF-beta 1 in the regulation of T cell responses.

Induction of mouse p55 interleukin-2 receptor gene expression by IL-2 and IL-4 and characterization of its transcription initiation sites

Two murine T cell lines (C30.1 and Line 1) were used to study the expression of the p55 interleukin-2 receptor gene. C30.1 is an IL-2-dependent T cell line that can be stimulated for a short period of time by IL-4. Line 1 cells are propagated in IL-4 but they also proliferate in response to IL-2. In both cell lines stimulation by IL-2 leads to a strong induction of p55 IL-2 receptor mRNA while stimulation by IL-4 leads only to a very moderate increase in expression of this mRNA. The induction of p55 IL-2 receptor mRNA by IL-4 is comparable to that of beta-actin mRNA. These data confirm that IL-2 upregulates p55 IL-2 receptor gene expression while IL-4, which also activates T cells, does not lead to specific induction of this gene. We have also determined the transcription initiation sites utilized by the p55 IL-2 receptor gene in C30.1 and Line 1 cells. Seven sites were identified, one of which predominates. Resting cells, or cells stimulated with IL-2 or IL-4, display the same pattern of transcription site utilization.

Role of ATL-derived factor (ADF) in the normal and abnormal cellular activation: involvement of dithiol related reduction

HTLV-I transformed T cells not only express a large number of interleukin-2 receptors (IL-2R/p55(Tac], but also produce an IL-2R/Tac inducer named ATL-derived factor (ADF). We have cloned the ADF cDNA and found that ADF production in human lymphocytes can be enhanced by cellular activators such as mitogens or phorbol esters. Recombinant ADF produced by E. coli was shown to have growth-promoting activity in combination with interleukin-2 or suboptimal mitogenic stimuli on several lymphoid cells including human PBMCs, besides the originally reported IL-2R/Tac inducing activity. Homology analysis revealed an unexpected structural relationship between ADF and dithiol-reducing enzyme, thioredoxin, which had been characterized originally in prokaryotic system. Recombinant ADF also has a reducing activity, suggesting the presence of still unknown features of ADF action in vivo. The requirement of dithiol reduction in the biological activities of ADF, together with the possible involvement of ADF production in the normal and abnormal activation of human cells are discussed.

Functionally distinct NF-kappa B binding sites in the immunoglobulin kappa and IL-2 receptor alpha chain genes

The interleukin-2 receptor alpha (IL-2R alpha) chain gene contains a sequence similar to the immunoglobulin (Ig) kappa (kappa) enhancer NF-kappa B binding site. This site, which is bound by the nuclear protein, NF-kappa B, is critical for Ig kappa gene expression. The major T cell nuclear factor that binds to the IL-2R alpha site in vitro appears indistinguishable from NF-kappa B. NF-kappa B binds to IL-2R alpha and kappa sequences with similar affinities; however, only the kappa site potently activates transcription from heterologous promoters. Thus, high-affinity NF-kappa B binding in vitro cannot be equated with transcriptional activation in vivo. Mutation of the NF-kappa B binding site in the context of an IL-2 R alpha promoter construct markedly diminished promoter activity in human T cell lymphotropic virus type I (HTLV-I)-transformed MT-2 cells but not in phorbol myristate acetate-stimulated Jurkat T cells.

Transcriptional regulation alone does not explain the constitutive expression of the interleukin 2 receptor (Tac/L-chain) in HTLV-1 infected cells

We have identified a suppressive element in the upstream region of the interleukin 2 (IL-2) receptor L chain (Tac) promoter. The inhibitory activity of this element was retained in human T cell leukemia virus type-1 (HTLV-1)-infected T cell lines which express constitutively a large number of IL-2 receptors on the cell surface. The promoter activities of the IL-2 receptor gene did not always correlate with the strong expression of the receptor and its mRNA in the HTLV-1-infected T cell lines we analysed. The results indicate that the constitutive up-regulation of the IL-2 receptor in HTLV-1-infected T cells may be ascribed to not only the transcriptional but also post-transcriptional regulation.

HTLV-1 transactivator induces interleukin-2 receptor expression through an NF-kappa B-like factor

Like other viruses that infect primate cells, the human T lymphotropic virus-I (HTLV-I) stimulates production of some host cell proteins. In particular, HTLV-I infected T cells synthesize interleukin-2 receptor alpha (IL-2R alpha) chain, which is probably induced through the mediation of the tat-I gene product of the virus. Activated T cells contain a trascription factor called NF-kappa B, which stimulates the expression of human immunodeficiency virus-1 (HIV-1) by binding to an 11-base-pair enhancer sequence called kappa B. We have now found evidence that a similar transcription factor is involved in the induction of IL-2R alpha expression by tat-I. We have identified a sequence upstream of IL-2R alpha which is the same as the kappa B site at 9 of 11 base pairs, competes for binding to the kappa B sequence, and serves as a tat-I responsive element when multiple copies are inserted upstream of a heterologous promoter. The tat-I product also induces kappa B and the IL-2R alpha kappa B binding activity in transfected Jurkat T lymphoid leukaemia cells. Both HTLV-I and HIV-1 thus interact with NF-kappa B-like transcription factors which might normally regulate expression of a growth factor receptor gene.