A novel transrepression pathway of c-Myc. Recruitment of a transcriptional corepressor complex to c-Myc by MM-1, a c-Myc-binding protein

The protooncogene product c-Myc plays a role in transcription regulation both for activation and repression. While transactivation pathways of c-Myc either from the N-proximal or the C-proximal region that is linked to the chromatin remodeling complex have been identified, a transrepression pathway had been identified only from the C-proximal region via Max and Mad that recruit the histone deacetylase (HDAC) complex. We have reported that a novel c-Myc-binding protein, MM-1, repressed the E-box-dependent transcription activity of c-Myc (Mori, K., Maeda, Y., Kitaura, H., Taira, T., Iguchi-Ariga, S. M. M., and Ariga, H. (1998) J. Biol. Chem. 273, 29794-29800). To clarify the molecular mechanisms of MM-1 toward c-Myc, cDNAs encoding MM-1-binding proteins were screened by the two-hybrid method with MM-1 as a bait using a human HeLa cDNA library, and a cDNA encoding TIF1 beta/KAP1, a transcriptional corepressor, was obtained. MM-1 was found to bind to the central portion of TIF1 beta in vitro and in vivo, and these proteins were found to be colocalized in the nucleus. MM-1 and TIF1 beta complex in human HeLa cells was found to also contain c-Myc, mSin3, and HDAC1. Introduction of the C-terminal half of TIF1 beta as a dominant negative form abrogated the inhibitory activity of MM-1 toward c-Myc and greatly stimulated the transcription activity of c-Myc. Moreover, the inhibitory activity of MM-1 toward c-Myc was canceled by trichostatin A, an inhibitor of HDAC1. These results indicate that MM-1 is a connecting factor that forms a novel transcription repression pathway of c-Myc.

Tumour invasion and metastasis are promoted in mice deficient in tenascin-X

BACKGROUND

Tenascin-X (TNX) is a member of the tenascin family of large oligomeric glycoproteins of the extracellular matrix (ECM). To determine whether TNX plays a part in tumour invasion and metastasis and to disclose its normal physiological role, we disrupted its gene in mouse embryonic stem cells by homologous recombination and created mice deficient in TNX.

RESULTS

TNX-null mutant (TNX-/-) mice arose at normal frequency and showed no obvious defects during their adult life. However, when TNX-/- mice were subcutaneously inoculated in foot-pads with a highly invasive and metastatic cell line, B16-BL6 melanoma cells, the primary tumour size at 30 days after inoculation in the TNX-/- mice had increased by 1.2-fold compared with that in wild-type mice, and the invasion to the ankle and pulmonary metastasis in TNX-/- mice were also augmented by 2.2-fold and 6.8-fold, respectively, compared to those in wild-type mice. To disclose the molecular mechanism(s) of the promotion of tumour invasion and metastasis in TNX-/- mice, we measured the protein levels of matrix metalloproteinases (MMPs), which are recognized as playing a key role in these events, in the foot-pad homogenates of TNX-/- mice prior to the inoculation of melanoma cells. Gelatin zymography showed that the activities of proMMP-2, active MMP-2 and proMMP-9 were significantly higher in TNX-/- mice than in wild-type mice. Furthermore, a Northern blot analysis demonstrated that this increased activity of MMP-2 in TNX-/- mice was due to the induced expression of MMP-2 at the transcriptional level. The elevated expression of MMP-2 and MMP-9 resulted in decreased laminin levels, to less than half that of wild-type mice in the homogenates of TNX-/- mice.

CONCLUSIONS

TNX deficiency led to an increase in the production of MMPs, and the increased activity of MMPs may result in the degradation of laminin. Consequently, the melanoma cells inoculated in TNX-/- mice might facilitate invasion and metastasis. These results imply that TNX is required for impeding the invasion and metastasis of tumour cells.

Disruption of MSSP, c-myc single-strand binding protein, leads to embryonic lethality in some homozygous mice

BACKGROUND

MSSP, c-myc single-strand binding protein, works as a factor for DNA replication, transcription, apoptosis induction, and myc/ras cooperative transformation. The cDNAs encoding four of the family proteins, MSSP-1, MSSP-2, Scr2 and Scr3, were cloned. These proteins possess two copies of putative RNA binding domains, RNP-A and RNP-B, and these RNA binding domains have been suggested to be indispensable to the functions of MSSP.

RESULTS

To elucidate its role in vivo, we generated Mssp knockout mice by homologous recombination in embryonic stem cells. Although intercrossing of Mssp+/- mice gave rise to mice homozygous to the mutant Mssp allele (Mssp-/-) and the Mssp-/- mice, once born, did not display an overt phenotype, the ratio of littermates born among Mssp+/+, Mssp+/- and Mssp-/- mice was 1 : 1.6 : 0.5, which is not a typical Mendelian ratio. When E2.5 embryos from the pregnant mice were cultured in vitro for 5 days, the inner cell mass and trophoblast giant cells in wild-type (Mssp+/+) E2.5 embryos developed normally. However, Mssp-/- E2.5 embryos displayed significant defects in growth and development. Since Mssp was expressed in uterine gland-transported glycogen, we evaluated the hormonal state of wild-type and Mssp-/- mice. The progesterone concentration of Mssp-/- mice was decrease to 6.5% of that of wild-type mice at E2.5.

CONCLUSIONS

These results suggest that the deletion of the mssp gene results in both the growth defect in the embryo and the hormonal defect in adult female mouse. The embryonic defect and a decreased concentration of progesterone in female mice reflect a development defect of the pre-implantation embryo in Mssp-/- mice, thereby leading to embryonic lethality.

Kinetics of fetal cellular and cell-free DNA in the maternal circulation during and after pregnancy: implications for noninvasive prenatal diagnosis

BACKGROUND

Fetal genetic material is detectable in the maternal circulation and has been used for noninvasive prenatal diagnosis. However, few data are available concerning its quantity and natural history during gestation.

STUDY DESIGN AND METHODS

This study prospectively characterized the kinetics of cellular and cell-free fetal DNA in the circulation of 25 healthy women during and after uncomplicated pregnancy. Real-time kinetic PCR was used to quantitate human Y-chromosome sequences, and liquid oligomer hybridization with (32)P-labeled probes was used to verify the identity of amplified products.

RESULTS

In all male pregnancies, but no female pregnancies, low-level fetal Y-chromosome DNA was detected in both cellular and cell-free compartments beginning at 7 to 16 weeks but increasing steadily after 24 weeks and reaching a peak at parturition. The fetal DNA decreased rapidly after birth.

CONCLUSION

Fetal genetic material can be detected throughout pregnancy, and its quantity is a function of gestational age and of whether the plasma or cellular compartment is examined. Both the absolute quantity of fetal DNA and its ratio to total DNA (maternal + fetal) are greater in the plasma than in the cellular compartment. Fetal DNA is cleared rapidly from both compartments after parturition, which suggests that turnover is dynamic. Because they provide prospective and quantitative data concerning fetal DNA levels, these observations and kinetic PCR methods may have implications for noninvasive prenatal diagnosis. Further studies will be needed to determine the immunologic implications of fetal-maternal DNA exchange and cellular microchimerism.

MM-1, a c-Myc-binding protein, is a candidate for a tumor suppressor in leukemia/lymphoma and tongue cancer

The c-myc oncogene product (c-Myc) is a transcription factor that dimerizes with Max and recognizes the E-box sequence, and it plays key functions in cell proliferation, differentiation, and apoptosis. We previously showed that MM-1 bound to myc box II within the transactivation domain of c-Myc and repressed the E-box-dependent transcriptional activity of c-Myc. Here we report that MM-1 showed features of a tumor suppressor. In an EST data base search for cDNAs homologous to MM-1, we found a frequent substitution of amino acid 157 of MM-1, from alanine to arginine (A157R), and the substitution was observed more in tumor cells than in normal cells. A survey of the A157R mutation of MM-1 in 57 cultured cancer cells and 90 tissues from cancer patients showed that the A157R was present in about 50-60% of leukemia/lymphoma cells and in more than 75% of squamous cell carcinoma of tongue cancer. Although both the A157R and the wild-type MM-1 bound to c-Myc, only A157R lost the activities to repress both the E-box-dependent transcriptional activity of c-Myc and the myc/ras cooperative transforming activity in rat 3Y1 cells. Furthermore, the wild-type MM-1, but not A157R, arrested the growth of 3Y1 cells. The human MM-1 gene was mapped at chromosome 12q12-12q13, where many chromosome abnormalities in cancer cells have been reported. The results suggest that MM-1 is a novel candidate for a tumor suppressor that controls the transcriptional activity of c-Myc.

Effect of tenascin-X together with vascular endothelial growth factor A on cell proliferation in cultured embryonic hearts

Tenascin-X (TNX) is a large glycoprotein that appears in extracellular matrices. Previously, we demonstrated that TNX binds to vascular endothelial growth factors A and B (VEGF-A and -B) and that VEGF-B in combination with TNX induces DNA synthesis in endothelial cells via increased signals mediated by the VEGFR-1 receptor. In this study, we investigated the effect of TNX with VEGF-A on the cell proliferation in embryonic mouse heart explants from either wild-type (TNX+/+) or TNX-deficient (TNX-/-) mice. The addition of VEGF-A to the explants from TNX+/+ mice increased cell proliferation by 1.5 fold compared with that in TNX-/- mice, indicating that TNX with VEGF family member plays an important role in the control of endothelial cell proliferation in vivo.

Radiation therapy for loco-regionally recurrent esophageal cancer after surgery

PURPOSE

To evaluate the treatment outcome of radiation therapy for 33 loco-regionally recurrent esophageal cancer patients.

METHODS

Between 1988 and 1997, 33 patients with loco-regional recurrence of esophageal cancer after curative surgery received radiation therapy at an average total dose of 61 Gy. The site of recurrence was the supraclavicular region in 14 patients, the mediastinal region in 13 patients, and both the supraclavicular and mediastinal regions in six patients. If patients had ether distant metastasis or malignant pleural effusion, they were excluded from analysis. Patients who received prophylactic postoperative irradiation were also excluded from analysis.

RESULTS

The median survival period was 7 months. The survival rates at 1, 2, and 3 years were 33, 15, and 12%, respectively. In univariate analysis, patients with a short time interval between surgery and recurrence (P=0.0098) and patients with recurrence in both the supraclavicular and mediastinal regions (P=0.036) had a worse prognosis. In multivariate analysis, the time interval between surgery and recurrence (P<0.001) and age (worse prognosis in younger patients, P=0.019) were the significant prognostic factors. Complete or partial responses were observed in nine (27%) and 21 (64%) of the patients, respectively. Changes in clinical symptoms, such as dysphagia, chest pain and back pain, could be evaluated in 11 patients, and improvement in symptoms was obtained in eight (73%) patients.

CONCLUSIONS

The prognosis of patients who received radiation therapy for postoperative loco-regional recurrence of esophageal cancer is poor. However, there is symptomatic relief in a significant proportion of such patients, and long-term survival is possible in some patients.

DJ-1 positively regulates the androgen receptor by impairing the binding of PIASx alpha to the receptor

DJ-1 was first identified as a novel candidate of the oncogene product that transformed mouse NIH3T3 cells in cooperation with an activated ras. Later DJ-1 was also found to be an infertility-related protein that was reduced in rat sperm treated with sperm toxicants that cause infertility in rats. To determine the functions of DJ-1, cDNAs encoding DJ-1-binding proteins were screened by the yeast two-hybrid method. Of several proteins identified, PIASx alpha/ARIP3, a modulator of androgen receptor (AR), was first characterized as the DJ-1-binding protein in this study. DJ-1 directly bound to the AR-binding region of PIASx alpha by an in vitro coimmunoprecipitation assay and also bound to PIASx alpha in human 293T cells. Both proteins were co-localized in the nuclei. PIASx alpha inhibited the AR transcription activity in a dose-dependent manner in cotransfected monkey CV1 cells with an androgen responsive element-luciferase reporter. Introduction of DJ-1 into CV1 cells in a state of inhibition of AR activity by PIASx alpha restored AR transcription activity by absorbing PIASx alpha from the AR-PIASx alpha complex, while a DJ-1 mutant harboring an amino acid substitution at number 130 from lysine to arginine did not restore it. These results indicate that DJ-1 is a positive regulator of the androgen receptor.

Pim-1 translocates sorting nexin 6/TRAF4-associated factor 2 from cytoplasm to nucleus

Pim-1, an oncogene product of serine/threonine kinase, has been found to play roles in apoptosis induction/suppression, cell-cycle progression and transcriptional regulation by phosphorylating the target proteins involved in these processes. The target proteins phosphorylated by Pim-1, including p100, Cdc25A, PAP-1 and heterochromatin protein 1, have been identified. The precise functions of Pim-1, however, are still poorly understood. In this study, we identified tumor necrosis factor receptor-associated factor 4-associated factor 2/sorting nexin 6 (TFAF2/SNX6) as a Pim-1-binding protein, and we found that TFAF2/SNX6 was phosphorylated and translocated from the cytoplasm to nucleus by Pim-1. This translocation of the protein was not affected by Pim-1-dependent phosphorylation. Since sorting nexins, including TFAF2/SNX6, have been reported to be located in the cytoplasm or membrane by association with several receptors of tyrosine- or serine/threonine-kinase, this is the first report of TFAF2/SNX6 being located in the nucleus after binding to Pim-1.

AMY-1, a c-Myc-binding protein, is localized in the mitochondria of sperm by association with S-AKAP84, an anchor protein of cAMP-dependent protein kinase

We have reported that a novel c-Myc-binding protein, AMY-1 (associate of Myc-1), stimulated the transcription activity of c-Myc. To access the molecular function of AMY-1, a two-hybrid screening of cDNAs encoding AMY-1-binding proteins was carried out with AMY-1 as a bait using a human HeLa cDNA library, and a clone encoding cAMP-dependent protein kinase anchor protein 149 (AKAP149), was obtained. AMY-1 was found to bind in vitro and in vivo to the regulatory subunit II binding region of AKAP149 and S-AKAP84, a splicing variant of AKAP149 expressed in the testis. AMY-1 was expressed postmeiotically in the testis, as S-AKAP84 was expressed. Furthermore, S-AKAP84 and regulatory subunit II, a regulatory subunit of cAMP-dependent protein kinase, made a ternary complex in cells, and AMY-1 was localized in the mitochondria of HeLa and sperm in association with AKAP149 and S-AKAP84, respectively. These results suggest that AMY-1 plays a role in spermatogenesis.

Initial symptoms of acute radiation syndrome in the JCO criticality accident in Tokai-mura

A criticality accident occurred on September 30, 1999, at the uranium conversion plant in Tokai-mura (Tokai-village), Ibaraki Prefecture, Japan. When the criticality occurred, three workers saw a "blue-white glow," and a radiation monitor alarm was sounded. They were severely exposed to neutron and gamma-ray irradiation, and subsequently developed acute radiation syndrome (ARS). One worker reported vomiting within minutes and loss of consciousness for 10-20 seconds. This worker also had diarrhea an hour after the exposure. The other worker started to vomit almost an hour after the exposure. The three workers, including their supervisor, who had no symptoms at the time, were brought to the National Mito Hospital by ambulance. Because of the detection of gamma-rays from their body surface by preliminary surveys and decreased numbers of lymphocytes in peripheral blood, they were transferred to the National Institute of Radiological Sciences (NIRS), which has been designated as a hospital responsible for radiation emergencies. Dose estimations for the three workers were performed by prodromal symptoms, serial changes of lymphocyte numbers, chromosomal analysis, and 24Na activity. The results obtained from these methods were fairly consistent. Most of the data, such as the dose rate of radiation, its distribution, and the quality needed to evaluate the average dose, were not available when the decision for hematopoitic stem cell transplantation had to be made. Therefore, prodromal symptoms may be important in making decisions for therapeutic strategies, such as stem-cell transplantation in heavily exposed victims.

Novel role of phosphatidylinositol 3-kinase in CD28-mediated costimulation

Ligation of the CD28 surface receptor provides a major costimulatory signal for full scale T cell activation. Despite extensive studies, the intracellular signaling pathways delivered by CD28 ligation are not fully understood. A particularly controversial matter is the role of phosphatidylinositol 3-kinase (PI3K) in CD28-mediated costimulation. It is known that the binding site for PI3K and Grb-2 lies nested within the YMNM motif of the CD28 cytoplasmic domain. To elucidate the role of PI3K during CD28-mediated interleukin-2 (IL-2) production, CD28 YMNM point and deletion mutants were expressed in Jurkat cells. We then measured IL-2 promoter activation after CD28 ligation. Our results showed that the Y189F mutant, which disrupts binding by PI3K, and the YMNM deletion mutant both demonstrated reduced but significant activity for IL-2 promoter activation. In contrast, the N191A mutant, which retains PI3K binding ability, resulted in a complete abrogation of activity, suggesting that PI3K mediates a negative effect upon transcriptional activation of the IL-2 gene. Consistent with this idea, we found that the addition of a PI3K pharmacological inhibitor augmented IL-2 promoter activity, whereas coexpression of a constitutively active form of PI3K reduced this activity. Taken together, these data indicate that PI3K, when associated with the YMNM motif, may act as a negative mediator in CD28-mediated IL-2 gene transcription.

Molecular cloning of human and mouse DJ-1 genes and identification of Sp1-dependent activation of the human DJ-1 promoter

DJ-1 has been identified as a novel oncogene that transforms mouse NIH3T3 cells in cooperation with activated ras. Subsequently, two other groups have identified SP22 or CAP-1, rat homologs of human DJ-1, as a sperm protein targeted by some toxicants leading to male infertility, and another group has also reported that RS, the same as human DJ-1, is a component of an RNA-binding protein complex. To characterize the expression or functional importance of DJ-1, the genomic DNAs of both human and mouse DJ-1 were cloned and characterized. Both genomic DNAs comprise 7 exons spanning about 16-24 kb, in which 2-6 exons encode the DJ-1 protein. The human DJ-1 gene was mapped at chromosome 1p36.2-p36.3, a region that has been shown to be a hot spot of chromosome abnormalities in several tumor cells. To analyze the promoter of the human DJ-1 gene, a series of deletion constructs of the region upstream of exon 2 were linked to the luciferase gene, and their luciferase activities were measured in human HeLa cells. Of the many putative transcription regulatory sequences, the Sp1 site present at -100 from the transcription initiation site contributed to the major promoter activity, and Sp1 was identified as a protein binding to this site by a mobility shift assay using HeLa nuclear extract.

Phase Ia study of a hypoxic cell sensitizer doranidazole (PR-350) in combination with conventional radiotherapy

A phase Ia study of a 2-nitroimidazole nucleoside analog radiosensitizer doranidazole was conducted to evaluate its toxicity and pharmacokinetics in patients undergoing conventional external beam radiotherapy. Twenty-nine patients, aged 40-74 years, with a WHO performance status of 0-2 and with adequate organ functions, were entered in the study. Single administration of doranidazole was investigated first with 13 patients and then a course of five consecutive daily administrations was tested in 16 patients. Doranidazole was given i.v. 25 min before irradiation. Doranidazole doses of 400, 800, 1300 and 2000 mg/m2 were evaluated in the former study, and daily doses of 800, 1300 and 2000 mg/m2 were investigated in the latter study. All patients tolerated doranidazole administration. Although a transient decrease in the 24-h creatinine clearance rate was observed in five patients (one in the single administration study and four in the repeat administration study), this was not considered to be the dose-limiting toxicity. Other toxicities (hematological and gastrointestinal), which may not be related to doranidazole administration, were also mild and were not dose limiting. No neurotoxicity was observed. The average maximum concentration, area under the time-concentration curve and half-life of doranidazole in serum were 172-194 microg/ml, 502-582 microg x h/l and 4.2-4.6 h, respectively, at 2000 mg/m2. At the tested doses, administration of doranidazole was tolerable and achieved serum concentrations at which reasonable radiosensitization could be expected. A phase Ib/II study to evaluate the feasibility and efficacy of up to 30 repeat administrations seems to be warranted.

Extracellular matrix tenascin-X in combination with vascular endothelial growth factor B enhances endothelial cell proliferation

BACKGROUND

An extracellular matrix tenascin-X (TNX) is highly expressed in muscular tissues, especially heart and skeletal muscle, and is also prominent around blood vessels. The precise in vivo role of TNX remains to be elucidated. To identify proteins that interact with TNX in the extracellular environment, we searched for TNX-binding proteins using a yeast two-hybrid system.

RESULTS

We used mouse TNX-specific fibronectin type III repeats (mTNX/FNIII13-25) as a bait for the screening. We found that vascular endothelial growth factor B (VEGF-B) binds to mTNX/FNIII13-25. This interaction was confirmed by pull-down assays and co-immunoprecipitation assays. The full-length mTNX, as well as mTNX/FNIII13-25, interacted with both alternative splice isoforms VEGF-B186 and VEGF-B167. Furthermore, the full-length mTNX also bound to VEGF-A. The minimal region of TNX that interacts with VEGF-B was mapped to the FNIII repeats (FNIII13-25) but not to the other characteristic domains of TNX. The TNX-binding site of VEGF-B was located in the N-terminal 115-amino acid region. mTNX/FNIII13-25 did not prevent the interaction of VEGF-B with VEGFR-1 (VEGF receptor 1), and VEGF-B could simultaneously bind to both mTNX/FNIII13-25 and VEGFR-1. A conditioned medium from transfected 293T cells coexpressing full-length TNX and VEGF-B could promote DNA synthesis in bovine endothelial cells in which VEGFR-1 were expressed. VEGFR-1 phosphorylation triggered by VEGF-B186 were increased in cells plated with mTNX/FNIII13-25 or full-length mTNX, compared with cells plated with VEGF-B186 alone.

CONCLUSION

TNX interacts with VEGF-B and enhances the ability of VEGF-B to stimulate cell proliferation. This enhanced mitogenecity is caused by increased signals mediated by the VEGFR-1 receptor. This finding suggests a role for TNX in the regulation of the development of blood vessels such as vasculogenesis and angiogenesis.

Expression and cellular localization of contraception-associated protein

Treatment of male rats with ornidazole results in reversible infertility, which is associated with the detection of the contraception-associated protein 1 (CAP1) in epididymal fluid. The protein, which is present in sperm but not detectable in epididymal fluid of fertile rats, seems to be shed from sperm during ornidazole administration. Cloning and characterization of the gene revealed a high degree of similarity between CAP1 and DJ-1 (Wagenfeld et al, 1998b) a protein that was recently found in humans and which has been classified as a novel oncogene. Reverse transcription of total ribonucleic acid (RNA) from various species indicated that a gene similar to CAP1 was also expressed in the testes of hamsters, mice, cynomolgus monkeys, and humans. Detection of RNA expression in rats at the cellular level by in situ hybridization revealed a stage-specific CAP1 expression in the cytoplasm of pachytene spermatocytes (stages IX-XIII), secondary spermatocytes (stage XIV), and round spermatids (stages I-VII). Immunolocalization of CAP1 in rat testis showed a strong staining of elongating spermatids (stages VI-VIII), indicating a translational delay of CAP1 expression. The location of CAP1 on sperm depended on the method of fixation used, with CAP1 being exhibited on the equatorial segment of the sperm head and cytoplasmic droplets. Flow cytometric analysis of sperm from ornidazole-fed rats revealed a significant decline (of 22%-24%) in the amount of sperm surface CAP1 compared with controls, which is associated with an altered location on the sperm head. These observations support a putative role of the protein in the fertilization process.

TOK-1, a novel p21Cip1-binding protein that cooperatively enhances p21-dependent inhibitory activity toward CDK2 kinase

A p21(Cip1/Waf1/Sdi1) is known to act as a negative cell-cycle regulator by inhibiting kinase activity of a variety of cyclin-dependent kinases. In addition to binding of the cyclin-dependent kinase to the N-terminal region of p21, p21 is also bound at its C-terminal region by proliferating cell nuclear antigen (PCNA), SET/TAF1, and calmodulin, indicating the versatile function of p21. In this study, we cloned cDNA encoding a novel protein named TOK-1 as a p21 C-terminal-binding protein by a two-hybrid system. Two splicing isoforms of TOK-1, TOK-1alpha and TOK-1beta, comprising 322 and 314 amino acids, respectively, were co-localized with p21 in nuclei and showed a similar expression profile to that of p21 in human tissues. TOK-1alpha, but not TOK-1beta, directly bound to the C-terminal proximal region of p21, and both were expressed at the G(1)/S boundary of the cell cycle. TOK-1alpha also preferentially bound to an active form of cyclin-dependent kinase 2 (CDK2) via p21, and these made a ternary complex in human cells. Furthermore, the results of three different types of experiments showed that TOK-1alpha enhanced the inhibitory activity of p21 toward histone H1 kinase activity of CDK2. TOK-1alpha is thus thought to be a new type of CDK2 modulator.

Extracellular signal regulated protein kinase and c-jun N-terminal kinase are involved in ml muscarinic receptor-enhanced interleukin-2 production pathway in Jurkat cells

We have previously shown that m1 and m2 muscarinic receptors were expressed on human peripheral blood lymphocytes (hPBL) and that pre-stimulation of these receptors enhanced phytohemagglutinin (PHA)-induced interleukin-2 (IL-2) production. Possible intracellular signal pathways of muscarinic receptors to regulate IL-2 production were examined in human T cell line Jurkat cells. Pretreatment of the cells with muscarinic receptor agonist, oxotremorine M (Oxo-M), enhanced IL-2 production induced by phorbol 12-myristate 13-acetate (PMA)/A23187, while Oxo-M by itself did not affect IL-2 production. The enhancement of IL-2 production by Oxo-M was inhibited by 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) an ml/m3 receptor antagonist. When the cells were pretreated with AF-DX116, an m2 antagonist, the IL-2 production enhanced by Oxo-M was further stimulated. Reverse transcription-polymerase chain reaction (RT-PCR) revealed that ml and m2 muscarinic receptors exist on Jurkat cells. The stimulation of ml receptors enhanced the PMA/A23187-induced binding activity to AP-1 consensus sequences in IL-2 promoter and production of c-Fos and c-Jun protein. The stimulation of ml receptors did not modify the DNA binding of NF-kappaB, NF-AT or Oct-1. When ml receptors were stimulated, activities of mitogen-activated protein kinase (MAPK)/extracellular signal regulated protein kinase (ERK) and c-Jun N-terminal kinase (JNK) were increased, while p38 MAPK was not affected. Incubation with Oxo-M induced a transient increase in [Ca2+]i, which was abolished by pretreatment with 4-DAMP. Treatment with cyclosporin A markedly decreased the PMA/A23187-induced IL-2 promoter activity. This treatment, however, did not affect the enhancement of the promoter activity induced by ml receptor stimulation. The results suggest that transcription factor AP-1 is involved in the ml receptor-mediated enhancement of IL-2 transcript in Jurkat cells, and that pathways via MAPK/ERK and JNK, but not via p38 MAPK, are involved in the ml receptor-mediated enhancement of IL-2 promoter activity.

PAP-1, a novel target protein of phosphorylation by pim-1 kinase

Protooncogene, pim-1, has been reported to be a predisposition for lymphomagenesis along with myc, and its protein product, Pim-1, has been shown to be a serine/threonine protein kinase, whose activity is involved in proliferation and differentiation of blood cells. The signal transduction pathways neither to nor from Pim-1, however, have been clarified. We have cloned a cDNA encoding a novel Pim-1 binding protein, PAP-1, comprising 213 amino acids with a basic amino-acid cluster near the C-terminus. PAP-1 was colocalized with Pim-1 in human HeLa cell nuclei. The in vitro binding assays using GST fusion proteins of the wild-type and various deletion mutants revealed that the whole molecule of Pim-1 is required for the binding activity to PAP-1 and that Pim-1 binds to the region from amino-acid numbers 1-147 of PAP-1, or to two segments in the region. The association of PAP-1 with Pim-1 was also shown in vivo in transfected cells. Furthermore, PAP-1 was phosphorylated in vitro by Pim-1, but not a kinase-negative Pim-1 mutant. The two serine residues of PAP-1 at amino acids 204 and 206 near the C-terminus were phosphorylated by Pim-1. PAP-1 is thus thought to be a target protein for Pim-1 kinase.

CDC6 interacts with c-Myc to inhibit E-box-dependent transcription by abrogating c-Myc/Max complex

The c-myc oncogene product (c-Myc) is a transcription factor that dimerizes with Max and recognizes the E-box sequence. It plays key functions in cell proliferation, differentiation and apoptosis. It is generally thought that c-Myc transactivates genes encoding proteins essential to cell-cycle progression by binding to the E-boxes that control them. The functions of c-Myc are also thought to be modulated by its associated proteins, several of which have recently been identified. In this study, we found that c-Myc directly bound in vivo and in vitro to the N-terminal region of human CDC6, a component of the pre-replication complex, and that both co-localized in cell nuclei. CDC6 bound to the C-proximal region of c-Myc, thereby competing with Max on the E-box sequence and changing c-Myc/Max heterodimer to a Max/Max homodimer. In consequence, the E-box-dependent transcription activity of c-Myc was abrogated. These results suggest that, in addition to its DNA replication activity, CDC6 also has a role as a transcriptional suppressor of c-Myc.

[A questionnaire survey on the self-assessment to the asthmatic treatment in Saitama Prefecture: results from 2825 cases]

The aim of this study was to survey the self-assessment to the treatment of adult bronchial asthmatics in Saitama prefecture. A questionnaire on daily symptoms and medications was distributed to 2825 adult asthmatic subjects who were treated at 125 hospitals/clinics in Saitama prefecture between September 15th and October 30th 1998. More than half (52.7%) of patients described that their general condition of asthma was poorly controlled. Even among the patients described that their condition was good or fair, 30.2% of them had some asthmatic symptoms such as shortness of breath or nocturnal awakening. Although inhaled corticosteroids were used in 66.2%, the ratio of patients who used spacer and kept drug compliance as prescribed were 59.6% and 45.8%, respectively. According to the physician's reports, cysteinyl leukotriene antagonist was used in 35.7%, which was comparable to the total of another anti-allergic drugs (37.3%). These results suggest that more than half of asthmatic patients in Saitama prefecture were not satisfied with their conditions of the disease control. Furthermore, more thorough education on the technique and compliance of inhaled corticosteroids would be required.

MSSP, a protein binding to an origin of replication in the c-myc gene, interacts with a catalytic subunit of DNA polymerase alpha and stimulates its polymerase activity

MSSP has been identified as a protein that binds to both single- and double-stranded sequences of a putative DNA replication origin sequence in the human c-myc gene. MSSP possesses versatile functions, including stimulation of DNA replication, transcriptional regulation, apoptosis induction, and cell transformation coordinated by c-Myc. MSSP contains two RNP domains, RNP1-A and RNP1-B, both of which are necessary for all of the functions of MSSP. In this study, we found that MSSP binds to the N-terminal region of a catalytic subunit of a human DNA polymerase alpha via its RNP domains both in vitro and in human cells. Furthermore, MSSP was released from the putative DNA replication origin of the c-myc gene after it complexed with DNA polymerase alpha, and MSSP stimulated DNA polymerase activity in vitro.

Primary structure, genomic organization and expression of the major secretory protein of murine epididymis, ME1

The mouse cDNA and its genomic clones encoding the epididymal secretory glycoprotein ME1 were identified. The Me1 gene spans 15kb with four exons and three introns. The deduced amino-acid sequence of the ME1 cDNA revealed that it consists of 149 amino acid residues, which contain a signal peptide characteristic of secretory proteins, six cysteine residues and a proline-rich region conserved in the orthologous proteins. Northern blot analysis revealed that 1.3kb ME1 mRNA is highly expressed in the mouse epididymis. The polyclonal antibodies generated against human HE1 (ME1 orthologous protein) expressed in bacteria reacted with approximately 17 to 25kDa components in mouse epididymis crude extract. The reduction of the molecular mass of the recombinant ME1 protein with the digestion of glycopeptidase A indicated that it is modified by Asn-linked glycosylation.