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2.  Radiation-quality-dependent bystander effects induced by the microbeams with different radiation sources 
Journal of Radiation Research  2014;55(Suppl 1):i54.
A central paradigm in radiation biology has been that only cells ‘hit’ by a track of radiation would be affected to induce radiobiological consequences, and cells ‘not hit’ should not be. This is the basis of the current system for risk estimation of radiobiological effects. However, it has recently been challenged by so-called non-targeted effects, such as bystander effect, and such radiation-induced cellular responses may have important implications for risk evaluation of low-dose-rate radiations as well as in tumor radiotherapy. Our group has been studying radiation-quality bystander cellular effects using the microbeams with different radiation sources.
It is essentially important for evaluating risk such a low-dose-rate exposure as the accident of Fukushima Daiichi Nuclear Power Plants to examine bystander effects induced by low-LET electromagnetic radiations, such as X or gamma rays. We have been studying the cellular responses in normal human fibroblasts by targeted cell nucleus irradiations with monochromatic X-ray microbeams (5.35 keV) produced by Photon Factory in High Energy Accelerator Research Organization. The results indicated that the bystander effect in cell- killing effect was observed in the targeted cell nucleus irradiation, not in the random irradiation containing both cell nucleus and cytoplasm by Poisson distribution. The results suggest that energy deposition in cytoplasm is an important role of inducing bystander effects in case of low-LET radiations.
We have also been investigating high-LET-radiation induced bystander effects using the heavy-ion microbeams at Takasaki Ion Accelerators for Advanced Radiation Application in Japan Atomic Energy Agency. Only 0.04% of the total numbers of normal human fibroblasts were irradiated with C-ion (220 MeV), Ne-ion (260 MeV) and Ar-ion (460 MeV) microbeams collimated at 20 μm in diameter. Cell-killing effect and gene mutation at HPRT locus in the cells irradiated with C ions were higher beyond our expectations and returned the estimated values that only 0.04% of the total cells were irradiated when using the specific inhibitor of gap junctions. On the other hand, no induced biological effects were observed in Ne and Ar ions whether the inhibitor was applied or not. The result suggested that the C-ion microbeam was capable of inducing bystander cellular effects via gap junction-mediated cell-cell communication. There is clear evidence that bystander cellular effects are dependent on radiation quality.
It is also important for highly developed heavy-ion radiotherapy to identify bystander effects induced by spatially low-fluence irradiations with heavy-ion beams. We have been investigating the biological effects using human tumor cell lines. The results clearly showed that bystander effects were observed in the carbon-ion irradiation but not in other ions as well as the effects in normal fibroblasts. Furthermore, the bystander cell-killing effect in tumor cell lines was strongly induced in the cells harboring wild-type P53 not in mutated-type P53 cells. The results provide the important implication for a tailor-made therapy using carbon ions.
PMCID: PMC3941530
Bystander effect; Microbeam; Gap junction, P53, HPRT
3.  Biosynthesis of 2-methylisoborneol in cyanobacteria 
The production of odiferous metabolites, such as 2-methlyisoborneol (MIB), is a major concern for water utilities worldwide. Although MIB has no known biological function, the presence of the earthy/musty taste and odor attributed to this compound result in the reporting of numerous complaints by consumers, which undermines water utility performance and the safe and adequate provision of potable waters. Cyanobacteria are the major producers of MIB in natural waters, by mechanisms that have heretofore remained largely unstudied. To investigate the fundamental biological mechanism of MIB biosynthesis in cyanobacteria, the genome of a MIB-producing Pseudanabaena limnetica was sequenced using Next Generation Sequencing and the recombinant proteins derived from the putative MIB biosynthetic genes were biochemically characterized. We demonstrate that the biosynthesis of MIB in cyanobacteria is a result of 2 key reactions: 1) a S-adenosylmethionine -dependent methylation of the monoterpene precursor geranyl diphosphate (GPP) to 2-methyl-GPP catalyzed by geranyl diphosphate 2-methyltransferase (GPPMT), and 2) further cyclization of 2-methyl-GPP to MIB catalyzed by MIB synthase (MIBS) as part of a MIB operon. Based on a comparison of the component MIB biosynthetic genes in actinomycetes and cyanobacterial organisms, we hypothesize that there have been multiple rearrangements of the genes in this operon.
PMCID: PMC3699865  PMID: 21174459
methylisoborneol; MIB; geosmin; taste; odor; water
5.  Inheritance pattern of familial moyamoya disease: autosomal dominant mode and genomic imprinting 
Although the aetiology of moyamoya disease (MMD) has not been fully clarified, genetic analysis of familial MMD (F‐MMD) has considerable potential to disclose it.
To determine the inheritance pattern and clinical characteristics of F‐MMD to enable precise genetic analyses of the disease.
15 highly aggregated Japanese families (52 patients; 38 women and 14 men) with three or more affected members were examined. The difference in categories of age at onset (child onset, adult onset and asymptomatic) between paternal and maternal transmission was compared by χ2 statistics.
In all families there had been three or more generations without consanguinity, and all types of transmission, including father‐to‐son, were observed. Among a total of 135 offspring of affected people, 59 (43.7%) were patients with MMD or obligatory carriers. Affected mothers were more likely to produce late‐onset (adult‐onset or asymptomatic) female offspring (p = 0.007).
The mode of inheritance of F‐MMD is autosomal dominant with incomplete penetrance. Thus, in future genetic studies on F‐MMD, parametric linkage analyses using large families with an autosomal dominant mode of inheritance are recommended. Genomic imprinting may be associated with the disease.
PMCID: PMC2077755  PMID: 16788009
6.  A phase I trial of S-1 with concurrent radiotherapy for locally advanced pancreatic cancer 
British Journal of Cancer  2007;96(11):1650-1655.
This study investigated the maximum tolerated dose of S-1 based on the frequency of its dose-limiting toxicities (DLT) with concurrent radiotherapy in patients with locally advanced pancreatic cancer. S-1 was administered orally at escalating doses from 50 to 80 mg m−2 b.i.d. on the day of irradiation during radiotherapy. Radiation therapy was delivered through four fields as a total dose of 50.4 Gy in 28 fractions over 5.5 weeks, and no prophylactic nodal irradiation was given. Twenty-one patients (50 three; 60 five; 70 six; 80 mg m−2 seven patients) were enrolled in this trial. At a dose of 70 mg m−2 S-1, two of six patients demonstrated DLT involving grade 3 nausea and vomiting and grade 3 haemorrhagic gastritis, whereas no patients at doses other than 70 mg m−2 demonstrated any sign of DLT. Among the 21 enrolled patients, four (19.0%) showed a partial response. The median progression-free survival time and median survival time for the patients overall were 8.9 and 11.0 months, respectively. The recommended dose of S-1 therapy with concurrent radiotherapy is 80 mg m−2 day−1. A multi-institutional phase II trial of this regimen in patients with locally advanced pancreatic cancer is now underway.
PMCID: PMC2359907  PMID: 17533388
pancreatic cancer; chemoradiotherapy; radiosensitizer; S-1; CA19-9
7.  Moderate Increase of Mean Daily Temperature Adversely Affects Fruit Set of Lycopersicon esculentum by Disrupting Specific Physiological Processes in Male Reproductive Development 
Annals of Botany  2006;97(5):731-738.
• Background and Aims Global warming is gaining significance as a threat to natural and managed ecosystems since temperature is one of the major environmental factors affecting plant productivity. Hence, the effects of moderate temperature increase on the growth and development of the tomato plant (Lycopersicon esculentum) were investigated.
• Methods Plants were grown at 32/26 °C as a moderately elevated temperature stress (METS) treatment or at 28/22 °C (day/night temperatures) as a control with natural light conditions. Vegetative growth and reproductive development as well as sugar content and metabolism, proline content and translocation in the androecium were investigated.
• Key Results METS did not cause a significant change in biomass, the number of flowers, or the number of pollen grains produced, but there was a significant decrease in the number of fruit set, pollen viability and the number of pollen grains released. Glucose and fructose contents in the androecium (i.e. all stamens from one flower) were generally higher in the control than METS, but sucrose was higher in METS. Coincidently, the mRNA transcript abundance of acid invertase in the androecium was decreased by METS. Proline contents in the androecium were almost the same in the control and METS, while the mRNA transcript level of proline transporter 1, which expresses specifically at the surface of microspores, was significantly decreased by METS.
• Conclusions The research indicated that failure of tomato fruit set under a moderately increased temperature above optimal is due to the disruption of sugar metabolism and proline translocation during the narrow window of male reproductive development.
PMCID: PMC2803419  PMID: 16497700
Lycopersicon esculentum; moderately elevated temperature stress; microsporogenesis; mean daily temperature; fruit set; pollen release; male reproductive development; tapetum; hexose; sucrose; acid invertase; proline transporter
9.  Phase II study of radiotherapy combined with gemcitabine for locally advanced pancreatic cancer 
British Journal of Cancer  2004;91(4):673-677.
PMCID: PMC2364779  PMID: 15226765
pancreatic cancer; chemoradiotherapy; gemcitabine; radiosentitiser
11.  Inactivation of class II transactivator by DNA methylation and histone deacetylation associated with absence of HLA-DR induction by interferon-γ in haematopoietic tumour cells 
British Journal of Cancer  2004;90(4):844-852.
PMCID: PMC2410180  PMID: 14970863
transcriptional coactivator; DNA methylation; histone acetylation
12.  Experience with International Neuroblastoma Staging System and Pathology Classification 
British Journal of Cancer  2002;86(7):1110-1116.
The International Neuroblastoma Staging System and Pathology Classification were proposed in 1988 and in 1999, respectively, but their clinical value has not yet been fully studied in new patients. Six hundred and forty-four patients with neuroblastoma treated between January 1995 and December 1999 were analysed by these classifications. The 4-year overall survival rate of patients <12 months of age with INSS stages 1, 2A, 2B, 3 and 4S disease was 98.5%, which was significantly higher than the 73.1% rate in stage 4 patients <12 months (P<0.0001). When patients were ⩾12 months, the 4-year overall survival rate of patients with neuroblastoma at 1, 2A, 2B and 3 stages was 100% and that of patients at stage 4 was 48.5% (P<0.0001). As to the International Neuroblastoma Pathology Classification histology, the 4-year overall survival rate was 98.8% in patients with favourable histology and 60.7% in those with unfavourable histology in the <12 months group (P<0.0001). In the ⩾12 months group, the 4-year oral survival of patients with favourable histology was 95.3% and that of patients with unfavourable histology was 50.6% (P<0.0001). Among biological factors, MYCN amplification, DNA diploidy and 1p deletions were significantly associated with poor prognosis in patients <12 months, as were MYCN amplification and DNA diploidy in patients ⩾12 months of age. Multivariate analysis showed that the INSS stage (stage 4 vs other stages) and International Neuroblastoma Pathology Classification histology (unfavourable vs favourable) were significantly and independently associated with the survival of patients undergoing treatment, stratified by age, stage and MYCN amplification (P=0.0002 and P=0.0051, respectively).
British Journal of Cancer (2002) 86, 1110–1116. DOI: 10.1038/sj/bjc/6600231
© 2002 Cancer Research UK
PMCID: PMC2364166  PMID: 11953858
neuroblastoma; International Neuroblastoma Staging System (INSS); International Neuroblastoma Pathology Classification (INPC); MYCN amplification; DNA ploidy; 1p deletion
13.  Apoptosis is a major mode of cell death caused by ischaemia and ischaemia/reperfusion injury to the rat intestinal epithelium 
Gut  1998;42(4):530-537.
Background and aims—Injuries caused by ischaemia and ischaemia/reperfusion in the small intestine have been widely accepted as resulting in necrosis. The aim of this study was to ascertain whether apoptosis also occurs. 
Methods—Intestinal epithelium from rats subjected to ischaemia (15-90 minutes) and ischaemia/reperfusion (15 minutes ischaemia followed by 15-75 minutes of reperfusion) was studied using histological, immunohistochemical, and molecular biological methods as well as FACS. 
Results—Mucosal injury was induced by both ischaemia and ischaemia/reperfusion. Detachment of epithelial cells from the villous stroma was an early morphological change indicating mucosal injury. More than 80% of the detached cells exhibited characteristic morphological features of apoptosis (condensation of chromatin and nuclear fragmentation). The remainder demonstrated necrotic features. The apoptotic cells eventually underwent spontaneous degeneration with membrane rupture, a process morphologically identical to necrosis. DNA fragmentation was also confirmed by immunohistochemical methods and agarose gel electrophoresis. 
Conclusion—Apoptosis is a major mode of cell death in the destruction of rat small intestinal epithelial cells induced by ischaemia and ischaemia/reperfusion injury. Disruption of epithelial cell-matrix interactions ("anoikis") may play an important part in induction of apoptosis in detached enterocytes. 

Keywords: ischaemia; reperfusion; apoptosis; necrosis; enterocyte; rat
PMCID: PMC1727054  PMID: 9616316
14.  Crystal structures of B-DNA with incorporated 2'-deoxy-2'-fluoro-arabino-furanosyl thymines: implications of conformational preorganization for duplex stability. 
Nucleic Acids Research  1998;26(10):2473-2480.
The fundamental conformational states of right-handed double helical DNA, the A- and B-forms, are associated with distinct puckers of the sugar moieties. The furanose conformation itself is affected by the steric and electronic nature of the ring substituents. For example, a strongly electronegative substituent at the C2' position, such as in the 2'-deoxy-2'-fluoro ribo furanosyl analogue, will drive the conformational equilibrium towards the C3'- endo type (north). Conversely, the 2'-deoxy-2'-fluoro arabino furanosyl modification with opposite stereochemistry at C2' appears to have a preference for a C2'- endo type pucker (south). Incorporation of 2'-fluoroarabinofuranosyl thymines was previously shown to enhance the thermodynamic stability of B-DNA duplexes. We have determined the crystal structures of the B-DNA dodecamer duplexes [d(CGCGAASSCGCG)]2and [d(CGCGAASTCGCG)]2with incorporated 2'-deoxy-2'-fluoroarabinofuranosyl thymines S (south) at 1.55 A resolution. In the crystal structures, all S residues adopt an O4'- endo conformation (east), well compatible with an overall B-form duplex geometry. In addition to the increased rigidity of S nucleosides, a clathrate-like ordered water structure around the 2'-fluorines may account for the observed larger thermodynamic stability of DNA duplexes containing 2'-deoxy-2'-fluoroarabino thymidines.
PMCID: PMC147554  PMID: 9580702
15.  The effect of two antipodal fluorine-induced sugar puckers on the conformation and stability of the Dickerson-Drew dodecamer duplex [d(CGCGAATTCGCG)]2. 
Nucleic Acids Research  1998;26(9):2237-2244.
UV thermal melting studies, CD and NMR spectroscopies were employed to assess the contribution of antipodal sugar conformations on the stability of the canonical B-DNA conformation of the Dickerson-Drew dodecamer duplex [[d(CGCGAATTCGCG)]2, (ODN 1)]. Different oligodeoxynucleotide versions of ODN 1 were synthesized with modified thymidine units favoring distinct sugar conformations by using a 3'- endo (north) 2'-fluoro-2'-deoxyribofuranosyl thymine (1) or a 2'- endo (south) 2'-fluoro-2'-deoxyarabinofuranosyl thymine (2). The results showed that two south thymidines greatly stabilized the double helix, whereas two north thymidines destabilized it by inducing a more A-like conformation in the middle of the duplex. Use of combinations of north and south thymidine conformers in the same oligo destabilized the double helix even further, but without inducing a conformational change. The critical length for establishing a detectable A-like conformation in the middle of a B-DNA ODN appears to be 4 bp. Our results suggest that manipulation of the conformation of DNA in a sequence-independent manner is possible.
PMCID: PMC147537  PMID: 9547286
16.  Fis is required for illegitimate recombination during formation of lambda bio transducing phage. 
Journal of Bacteriology  1997;179(13):4239-4245.
Specialized transducing particles of phage lambda are formed by illegitimate recombination during prophage induction. We examined the effects of an Esherichia coli int, xis, himA, himD, or fis mutation on illegitimate recombination during formation of lambda Spi- phage, a class of lambda bio transducing phage. This type of phage is distinguishable from the docL and docR particles, which contain one cohesive end and are formed by cutting of the cos site, by plaque formation of lambda bio on Escherichia coli P2 lysogens. The yields of lambda Spi- phage in the int, xis, int-xis deletion, and b2 deletion mutants were about 50- to 200-fold higher than that of the wild-type prophage when bacteria were irradiated with UV light. This result indicates that Int and Xis functions, and the att site, are not required for illegitimate recombination. The yield of lambda Spi- phage in the himA, himD, or fis mutant carrying lambda delta int-xis prophage was 2.6-, 3.3-, or 17-fold lower, respectively, than that in the wild-type bacteria under UV irradiation. Analysis of the nucleotide sequences of the junctions of the transducing phages indicates that recombination at the hotspots, as well as at non-hotspots, takes place between short homologous sequences. Because the growth of infecting phages was not suppressed by the himA, himD, or fis mutation, we conclude that Fis is required, but IHF is only partially required, for short-homology-dependent illegitimate recombination during the formation of lambda bio transducing phage.
PMCID: PMC179245  PMID: 9209039
17.  Molecular analysis of p21 and p27 genes in human pituitary adenomas. 
British Journal of Cancer  1997;76(9):1119-1123.
Pituitary tumours develop at a high frequency in p27-knockout mice and retinoblastoma gene-knockout mice, which suggests that cell cycle regulatory genes, such as cyclin-dependent kinase inhibitor genes, are involved in the tumorigenesis of pituitary adenoma. Analysis of p21 and p27 gene abnormalities in human pituitary adenoma was performed in 28 pituitary adenomas by polymerase chain reaction-single-strand conformational polymorphism. No point mutations were detected in these genes. As no abnormalities of the p21 and p27genes were observed, and if these genes are indeed inactivated, it is likely to be via transcriptional or translational defects.
PMCID: PMC2228124  PMID: 9365157
18.  Hdf1, a yeast Ku-protein homologue, is involved in illegitimate recombination, but not in homologous recombination. 
Nucleic Acids Research  1996;24(11):2067-2072.
Hdf1 is the yeast homologue of the mammalian 70 kDa subunit of Ku-protein, which has DNA end-binding activity and is involved in DNA double-strand break repair and V(D)J recombination. To examine whether Hdf1 is involved in illegitimate recombination, we have measured the rate of deletion mutation caused by illegitimate recombination on a plasmid in an hdf1 disruptant. The hdf1 mutation reduced the rate of deletion formation by 20-fold, while it did not affect mitotic and meiotic homologous recombinations between two heteroalleles or homologous recombination between direct repeats. Hence Hdf1 participates in illegitimate recombination, but not in homologous recombination, in contrast to Rad52, Rad50, Mre11 and Xrs2, which are involved in both homologous and illegitimate recombination. The illegitimate recombination in the hdf1 disruptant took place between recombination sites that shared short regions of homology (1-4 bp), as was observed in the wild-type. Based on the DNA end-binding activity of Hdf1, we discuss models in which Hdf1 plays an important role in the late step of illegitimate recombination.
PMCID: PMC145893  PMID: 8668537
19.  Role of the recJ gene product in UV-induced illegitimate recombination at the hotspot. 
Journal of Bacteriology  1996;178(8):2362-2367.
Illegitimate recombination between a prophage and adjacent bacterial DNA is the first step in the formation of specialized transducing phage. Such recombination is rare, but it is greatly enhanced by UV irradiation. We studied the mechanism of UV-induced illegitimate recombination by examining the effect of rec mutations on the frequency of lambda bio transducing phage and found that an Escherichia coli recJ mutation reduces it by 3- to 10-fold. In addition, the recombination hotspot, which accounts for approximately 60% of lambda bio transducing phages in wild-type bacteria, was not detected in the recJ mutant. Introduction of a RecJ overexpression plasmid into the recJ mutant recovered the recombination at the hotspot. These results indicate that the RecJ protein preferentially stimulates illegitimate recombination at the hotspot. Both the hotspot and the non- hotspot sites have short regions of homology, but only the hotspot sites contain common direct-repeat sequences. We propose a model based on the 5'-3' exonuclease activity of RecJ to explain the involvement of this protein in illegitimate recombination at the hotspot.
PMCID: PMC177946  PMID: 8636039
20.  Quinolone-resistant mutants of escherichia coli DNA topoisomerase IV parC gene. 
Escherichia coli quinolone-resistant strains with mutations of the parC gene, which codes for a subunit of topoisomerase IV, were isolated from a quinolone-resistant gyrA mutant of DNA gyrase. Quinolone-resistant parC mutants were also identified among the quinolone-resistant clinical strains. The parC mutants became susceptible to quinolones by introduction of a parC+ plasmid. Introduction of the multicopy plasmids carrying the quinolone-resistant parC mutant gene resulted in an increase in MICs of quinolones for the parC+ and quinolone-resistant gyrA strain. Nucleotide sequences of the quinolone-resistant parC mutant genes were determined, and missense mutations at position Gly-78, Ser-80, or Glu-84, corresponding to those in the quinolone-resistance-determining region of DNA gyrase, were identified. These results indicate that topoisomerase IV is a target of quinolones in E. coli and suggest that the susceptibility of E. coli cells to quinolones is determined by sensitivity of the targets, DNA gyrase and topoisomerase IV.
PMCID: PMC163185  PMID: 8851598
21.  Soluble interleukin-6 receptors in inflammatory bowel disease: relation to circulating interleukin-6. 
Gut  1995;36(1):45-49.
The in vivo appearance of soluble interleukin (IL)-6 receptor (sIL-6R) in serum from patients with inflammatory bowel disease was examined using an enzyme linked immunosorbent assay (ELISA). The serum sIL-6R concentrations in patients with active disease (ulcerative colitis, 148.4 (5.1); Crohn's disease, 142.3 (9.3) ng/ml; mean (SEM)) were significantly raised compared with those in patients with inactive disease (ulcerative colitis, 116.2 (7.2); Crohn's disease, 114.3 (7.1) ng/ml), some other type of colitis (104.8 (11.6) ng/ml), or in normal subjects (107.3 (2.4) ng/ml). These differences were also seen in paired samples examined during both active and inactive phases. Additionally, serum sIL-6R and IL-6 concentrations correlated significantly with C-reactive protein levels in both ulcerative colitis and Crohn's disease patients (r = 0.23 and 0.56, respectively; p < 0.05 for both). Furthermore, gel filtration analysis of serum from these patients showed two major peaks of immunoreactive IL-6-one peak corresponding to free IL-6 and another peak to sIL-6R-bound IL-6-this was further confirmed by a luminescence sandwich ELISA. These results, together with its in vitro effects, indicate that natural sIL-6R may function as a powerful enhancer of the IL-6-dependent immune processes observed in inflammatory bowel disease.
PMCID: PMC1382351  PMID: 7890234
22.  Comparison of inhibition of Escherichia coli topoisomerase IV by quinolones with DNA gyrase inhibition. 
Antimicrobial Agents and Chemotherapy  1994;38(11):2623-2627.
In order to examine the inhibitory activities of quinolones against topoisomerase IV, both subunits of this enzyme, ParC and ParE, were purified from Escherichia coli. The specific activity of topoisomerase IV decatenation was found to be more than five times greater than that of topoisomerase IV relaxation. Thus, the decatenation activity of topoisomerase IV seems the most relevant activity for use in studies of drug inhibition of this enzyme. Although topoisomerase IV was less sensitive to quinolones than DNA gyrase, the 50% inhibitory concentrations for decatenation were significantly lower than those for type I topoisomerases. Moreover, there was a positive correlation between the inhibitory activity against topoisomerase IV decatenation and that for DNA gyrase supercoiling. These results imply that topoisomerase IV could be a target for the quinolones in intact bacteria and that quinolones could inhibit not only supercoiling of DNA gyrase but also decatenation of topoisomerase IV when high concentrations of drug exist in bacterial cells.
PMCID: PMC188252  PMID: 7872758
23.  Clonal expansion of CD8+ cytotoxic T lymphocytes against human T cell lymphotropic virus type I (HTLV-I) genome products in HTLV-I-associated myelopathy/tropical spastic paraparesis patients. 
Journal of Clinical Investigation  1994;94(5):1830-1839.
Short-term culture of peripheral blood mononuclear cells (PBMC) derived from patients with human T cell lymphotropic virus type I-associated myelopathy (HAM)/tropical spastic paraparesis resulted in dominance by DR+ activated CD8+ T cells. Variations in the T cell receptor (TCR) V alpha and V beta chains in these cells were analyzed, and in all 10 patients examined, 2-3 V gene families were dominant in both TCR V alpha and V beta. In five patients we examined, cultured lymphocytes contained cytotoxic lymphocytes for p40tax (patients HAM2, 3, 7, and 8) or env protein (patient HAM4) of human T lymphotropic virus type I. In patients HAM2 and HAM8, cultured lymphocytes contained a large proportion of V beta 8+ CD8+ and/or V beta 12+ CD8+ cells. The sequence of V beta 8+ and V beta 12+ cDNA revealed that they were oligoclonal with identical or similar sequences in each patient. Elimination experiments with monoclonal antibodies for TCR V beta 8 and V beta 12 showed that they were CD8+ cytotoxic T lymphocytes (CTL) for p40tax. In addition, flow cytometry and sequencing analysis of uncultured PBMC revealed that in HAM2, V beta 8+ CTL and their precursors account for 7% and V beta 12+ CTL and their precursors account for 18% of total CD8+ cells. This indicates the presence of two markedly expanded clones in vivo. No common dominant TCR V alpha or V beta were observed among 10 HAM patients analyzed.
PMCID: PMC294583  PMID: 7962528
24.  Homologous recombination of monkey alpha-satellite repeats in an in vitro simian virus 40 replication system: possible association of recombination with DNA replication. 
Molecular and Cellular Biology  1994;14(6):4173-4182.
To study homologous recombination between repeated sequences in an in vitro simian virus 40 (SV40) replication system, we constructed a series of substrate DNAs that contain two identical fragments of monkey alpha-satellite repeats. Together with the SV40-pBR322 composite vector encoding Apr and Kmr, the DNAs also contain the Escherichia coli galactokinase gene (galK) positioned between two alpha-satellite fragments. The alpha-satellite sequence used consists of multiple units of tandem 172-bp sequences which differ by microheterogeneity. The substrate DNAs were incubated in an in vitro SV40 DNA replication system and used to transform the E. coli galK strain DH10B after digestion with DpnI. The number of E. coli galK Apr Kmr colonies which contain recombinant DNAs were determined, and their structures were analyzed. Products of equal and unequal crossovers between identical 172-bp sequences and between similar but not identical (homeologous) 172-bp sequences, respectively, were detected, although those of the equal crossover were predominant among all of the galK mutant recombinants. Similar products were also observed in the in vivo experiments with COS1 cells. The in vitro experiments showed that these recombinations were dependent on the presence of both the SV40 origin of DNA replication and SV40 large T antigen. Most of the recombinant DNAs were generated from newly synthesized DpnI-resistant DNAs. These results suggest that the homologous recombination observed in this SV40 system is associated with DNA replication and is suppressed by mismatches in heteroduplexes formed between similar but not identical sequences.
PMCID: PMC358783  PMID: 8196655
25.  Identification of mutations in the coding sequence of the proto-oncogene c-kit in a human mast cell leukemia cell line causing ligand-independent activation of c-kit product. 
Journal of Clinical Investigation  1993;92(4):1736-1744.
The c-kit proto-oncogene encodes a receptor tyrosine kinase. Binding of c-kit ligand, stem cell factor (SCF) to c-kit receptor (c-kitR) is known to activate c-kitR tyrosine kinase, thereby leading to autophosphorylation of c-kitR on tyrosine and to association of c-kitR with substrates such as phosphatidylinositol 3-kinase (PI3K). In a human mast cell leukemia cell line HMC-1, c-kitR was found to be constitutively phosphorylated on tyrosine, activated, and associated with PI3K without the addition of SCF. The expression of SCF mRNA transcript in HMC-1 cells was not detectable by means of PCR after reverse transcription (RT-PCR) analysis, suggesting that the constitutive activation of c-kitR was ligand independent. Sequencing of whole coding region of c-kit cDNA revealed that c-kit genes of HMC-1 cells were composed of a normal, wild-type allele and a mutant allele with two point mutations resulting in intracellular amino acid substitutions of Gly-560 for Val and Val-816 for Asp. Amino acid sequences in the regions of the two mutations are completely conserved in all of mouse, rat, and human c-kit. In order to determine the causal role of these mutations in the constitutive activation, murine c-kit mutants encoding Gly-559 and/or Val-814, corresponding to human Gly-560 and/or Val-816, were constructed by site-directed mutagenesis and expressed in a human embryonic kidney cell line, 293T cells. In the transfected cells, both c-kitR (Gly-559, Val-814) and c-kitR (Val-814) were abundantly phosphorylated on tyrosine and activated in immune complex kinase reaction in the absence of SCF, whereas tyrosine phosphorylation and activation of c-kitR (Gly-559) or wild-type c-kitR was modest or little, respectively. These results suggest that conversion of Asp-816 to Val in human c-kitR may be an activating mutation and responsible for the constitutive activation of c-kitR in HMC-1 cells.
PMCID: PMC288334  PMID: 7691885

Results 1-25 (53)