Regulation mechanisms of mammalian telomerase. A review

In this review, I summarize the most recent progress in the studies on mammalian telomerase, especially focusing on the molecular aspects. Possible regulation mechanisms of telomerase activity in mammalian cells are discussed.

ICE: a novel and efficient method for isolation of chromosomal ends

The linear chromosomal ends are usually unclonable by general methods due to a lack of restriction sites. We present a novel method, isolation of chromosomal ends (ICE), which has been developed for the efficient isolation of linear DNA ends.

Telomere crisis in leukemia

Previous studies on telomere dynamics in leukemia are summarized. The 'telomere crisis model' is proposed to explain the clonal evolution mechanism of cancer cells from the standpoint of telomere biology. Future trends, including the development of potential telomerase inhibitors as a new class of anti-cancer agent, are discussed.

TLP1: a gene encoding a protein component of mammalian telomerase is a novel member of WD repeats family

We have cloned and characterized the rat telomerase protein component 1 gene (TLP1), which is related to the gene for Tetrahymena p80. The cDNA encodes a 2629 amino acid sequence and produces the TLP1 proteins p240 and p230. The anti-TLP1 antibody specifically immunoprecipitated the telomerase activity. Moreover, p240 and p230 were copurified with telomerase activity in a series of extensive purification experiments. These results strongly suggest that the TLP1 proteins are components of, or are closely associated with, the rat telomerase. A pulse-chase experiment showed that p240 is modified to p230 in vivo. p230 was the dominant form in telomerase-positive cells, suggesting that modification of the TLP1 protein may regulate telomerase activity in vivo.

Telomere crisis, the driving force in cancer cell evolution

Cancer cells show characteristic telomere dynamics. Their chromosomes usually have short telomeres and a high telomerase activity. The "telomere crisis model" proposed here suggests that these unique telomeric features are responsible for the progression of cancer.

[A case of hemolysis induced by lansoprazole]

Hemolytic anemia and possible aplastic crisis with symptoms including jaundice, general fatigue and dark urine developed in a man being treated only by lansoprazole. Five days later, he was treated with antibiotics. The next day, he was admitted to our hospital because of jaundice. On admission, the hemoglobin was 14.0 g/dl, reticulocyte count 8/1000, platelets 79 x 10(9)/l and total bilirubin 12.4 mg/dl (indirect bilirubin 9.5 mg/dl). The above medications were discontinued. The direct Coombs antiglobulin test was positive. Examination of the complement revealed a C3 fiter at the upper limit of normal and an increased C4 and CH50. Three days after admission, he had a severe anemia. The hemoglobin was 3.3 g/DL. We thought it possible that aplastic crisis had followed the hemolytic anemia induced by lansoprazole. He was treated with blood transfusions and corticosteroids. He recovered from anemia within three weeks. Exhaustive studies to identify the cause of the hemolytic anemia were undertaken with negative results. We detected IgG antibody to lansoprazole. We believe that the hemolytic anemia was induced by lansoprazole.

[Telomere and telomerase]

Telomeres are the functional domains positioned at the ends of chromosomes. It is essential for the stable maintenance of chromosomes. Telomerase is an enzyme that has an important role in the DNA replicator at telomeres. Its activity is specifically activated in cancer cells. We have reported a novel specific and sensitive assay (stretch RCR assay) for the detection of telomerase activity. We analyzed the telomerase activity in leukemias using this method. The results showed that telomerase is specifically activated during the progression stages of leukemia. The "telomere crisis model" has been proposed for explaining the role of the telomere dynamics in malignancies.

A novel quantitative 'stretch PCR assay', that detects a dramatic increase in telomerase activity during the progression of myeloid leukemias

Telomerase activation is important for carcinogenesis. However, the timing and magnitude of the activation during cancer development are unknown. In this study, a new PCR-based method for measuring telomerase activity was developed and shown to be very useful for quantitative analysis of human telomerase. Using this assay, blood or bone marrow cells from healthy donors, and patients with chronic myelogenous leukemia (CML) and acute myelogenous leukemia (AML) were examined as to their relative activity. Telomerase activity present in normal peripheral blood cells was generally very low. However, significant activity was detected occasionally in samples derived from younger healthy donors. Striking telomerase activation was observed at the time of the blastic crisis in CML: no samples from chronic phase cases showed significant activity, while all cases with a well established crisis showed strong activity. Most AML cases were telomerase-positive. Quantitative analyses revealed that the relative titer varied among the AML patients, from as low as found in normal cells to as high as found in cell lines. However, a tendency that the activity was higher in relapsed cases than in fresh ones was suggested. In summary, telomerase was activated during the progression of the clinical stages in leukemias. This observation suggests that shortened telomeres and increased telomerase activity might be necessary for cancer cells to undergo clonal evolution towards more malignant phenotypes in advanced stages.

[An adhesion dependent injury of target cell membrane by NK cell surface associated metaloprotease]

Natural killer (NK) cytotoxicity was assayed with P3-X63-Ag8-U1 (P3U-1) target cells which had been previously demonstrated to release endogenous alkaline phosphatase (AlP) on the attack of lymphocyte-activated killer cells). P3U-1 cells showed a definite sensitivity to the AlP-release test, but no response in the Cr-release test at all. The AlP-release was not inhibited by anti-perforin antibody, benzoate, phenyl-methyl-sulfonyl-fluoride, soybean trypsin inhibitor, Succinyl-Gly-Pro-Leu-Gly-Pro-amino-methyl-coumarin, or gamma-radiation to effector cells, but was inhibited by o-phenanthroline, anti-CD13 antibody, and anti-LFA-1 alpha antibody. The AlP-release from P3U-1, therefore, did not appear to be brought on by the NK cell-derived perforin, hydroxy-radical, granzymes or cytosolic proteases. The inhibition by o-phenanthroline and the antibody for CD13 (aminopeptidase N) or the adhesion factor in NK cells, however, indicated that the membrane of such cells with adhesion ligand to NK cells was probably susceptible to NK cell surface-associated metaloprotease in an adhesion dependent manner to the extent of some injury without complete perforation through the membrane.

Bioluminescent detection of RNA with sequence-specificity using RNA binding protein-luciferase fusion protein

A novel bifunctional reagent has been synthesized for RNA detection by genetic fusion of a sequence-specific RNA binding protein and firefly luciferase. The RNA binding protein used in this study recognizes the oligoribonucleotide rH4 which contains four (UUAGGG)-repeat sequence, while luciferase works as a bioluminescent marker. The constructed fusion protein exhibited both sequence-specific RNA binding and bioluminescent activities. The rH4 and rECGF, which has an unrelated sequence having the same length as rH4, were immobilized on a nylon membrane. The membrane was pre-treated by 5% bovine serum albumin and soaked into a fusion protein solution. Bioluminescent detection has successfully been performed at more than 50 pmol of rH4, so the detection limit using this protein was 50 pmol. However, no appreciable bioluminescence was induced by rECGF.

Isolation and identification of seven metabolites of a water-soluble platelet aggregation inhibitor in rat urine

1. Seven metabolites of 7-piperidino-1,2,3,4,5-tetrahydroimidazo[2,1- b]quinazolin-2-one dihydrochloride monohydrate (DN-9693) were isolated from rat urine by extraction with Amberlite XAD-2 and purification by silica gel and Sephadex LH-20 open-column chromatography and preparative high-performance liquid chromatography (hplc). The structure assignment of the metabolites was performed by field desorption mass spectrometry and 200-MHz Fourier transform nmr spectroscopic analysis and comparison with authentic standards when available. 2. DN-9693 underwent metabolism mainly at the piperidine ring to give the 4-hydroxypiperidine derivative (III) and 2-hydroxy-piperidine derivative, which is further metabolized to lactam (II) or delta-aminovaleric acid (V). The acyl side chain of V was shortened by beta-oxidation to form the 3-aminopropionic acid derivative (VII). V and/or VII underwent oxidative dealkylation to give the 7-amino derivative, which was conjugated with acetic acid to form the 7-acetylamino derivative (IV). DN-9693 also underwent hydrolysis of its lactam moiety to give VI. 3. The urinary excretion of III, V and VII was determined by liquid chromatography/electrochemistry (LC/EC) and V proved to be the major metabolite in rat urine. 4. A procedure is also presented for the identification of DN-9693 metabolites using LC/EC.

The UUAG-specific RNA binding protein, heterogeneous nuclear ribonucleoprotein D0. Common modular structure and binding properties of the 2xRBD-Gly family

Human cDNA clones encoding the UUAG-binding heterogeneous nuclear ribonucleoprotein (hnRNP) D0 protein have been isolated and expressed. The protein has two RNA-binding domains (RBDs) in the middle part of the protein and an RGG box, a region rich in glycine and arginine residues, in the C-terminal part ("2xRBD-Gly" structure). The hnRNP A1, A2/B1, and D0 proteins, all possess common features of the 2xRBD-Gly structure and binding specificity toward RNA. Together, they form a subfamily of RBD class RNA binding proteins (the 2xRBD-Gly family). One of the structural characteristics shared by these proteins is the presence of several isoforms presumably resulting from alternative splicing. Filter binding assays, using the recombinant hnRNP D0 proteins that have one of the two RBDs, indicated that one RBD specifically binds to the UUAG sequence. However, two isoforms with or without a 19-amino acid insertion at the N-terminal RBD showed different preference toward mutant RNA substrates. The 19-amino acid insertion is located in the N-terminal end of the first RBD. This result establishes the participation of the N terminus of RBD in determining the sequence specificity of binding. A similar insertion was also reported with the hnRNP A2/B1 proteins. Thus, it might be possible that this type of insertion with the 2xRBD-Gly type RNA binding proteins plays a role in "fine tuning" the specificity of RNA binding. RBD is supposed to bind with RNA in general and sequence-specific manners. These two discernible binding modes are proposed to be performed by different regions of the RBD. A structural model of these two binding sites is presented.

Purification of Treponema pallidum, Nichols strain, by two-step column chromatography

A rapid and simple purification method for Treponema pallidum, Nichols strain, the etiological agent of venereal syphilis, was developed. A 40-ml suspension of organisms (1.10(9)/ml) was extracted from rabbit testicular tissue and solubilized with a non-ionic detergent, 1-O-n-octyl-beta-D-glucopyranoside. Solubilized antigens were purified by cation-exchange and hydroxyapatite column chromatography. The overall recovery of immunoreactive material was 48.3% and the specific activity increased. Sodium dodecyl sulphate polyacrylamide gel electrophoresis and immunoblotting analysis confirmed the purity and species specificity of the purified antigen.

[Cytotoxicity test based on luminescent assay of alkaline phosphatase released from target cells]

Assay of 51Cr release from target cells has been commonly used in various methods of examining the cytotoxic properties of lymphocytes. In this paper a non-isotopic assay of cytotoxicity based on the leak of endogenous alkaline phosphatase (AIP) in target cells, is described. Enzyme activities were assayed by the luminescence on hydrolysis of the lumigen-PPD substrate. P3-X63-Ag8-U1 (P3U-1) cells were demonstrated to contain AIP and proved sensitive to the IL-2-induced killer lymphocytes, while no AIP activity was detected in human effector lymphocytes. Comparative studies of the test with 51Cr- and AIP-release in P3U-1 target cells were carried out, and the results obtained suggested that the AIP release test is useful as a new, simple lymphocyte cytotoxicity test.

Latex agglutination test for detecting antibodies to Treponema pallidum

We have developed an automated latex agglutination test for Treponema pallidum (TPLA) for measurement of the concentration of treponemal antibodies in syphilitic sera. The assay needs neither a complicated pretreatment of the sera nor special techniques. Intra- and interassay precision studies showed high reproducibility. Potentially interfering substances, such as bilirubin, hemoglobin, triglycerides, and rheumatoid factor, did not affect the results. The results obtained with the TPLA test showed a strong correlation with those from conventional methods. This test for antibodies to T. pallidum may be useful for the mass screening of syphilitic infections.

Latex agglutination test for detecting antibodies to Treponema pallidum

We have developed an automated latex agglutination test for Treponema pallidum (TPLA) for measurement of the concentration of treponemal antibodies in syphilitic sera. The assay needs neither a complicated pretreatment of the sera nor special techniques. Intra- and interassay precision studies showed high reproducibility. Potentially interfering substances, such as bilirubin, hemoglobin, triglycerides, and rheumatoid factor, did not affect the results. The results obtained with the TPLA test showed a strong correlation with those from conventional methods. This test for antibodies to T. pallidum may be useful for the mass screening of syphilitic infections.

Nuclear proteins that bind the pre-mRNA 3' splice site sequence r(UUAG/G) and the human telomeric DNA sequence d(TTAGGG)n

HeLa cell nuclear proteins that bind to single-stranded d(TTAGGG)n, the human telomeric DNA repeat, were identified and purified by a gel retardation assay. Immunological data and peptide sequencing experiments indicated that the purified proteins were identical or closely related to the heterogeneous nuclear ribonucleoproteins (hnRNPs) A1, A2-B1, D, and E and to nucleolin. These proteins bound to RNA oligonucleotides having r(UUAGGG) repeats more tightly than to DNA of the same sequence. The binding was sequence specific, as point mutation of any of the first 4 bases [r(UUAG)] abolished it. The fraction containing D and E hnRNPs was shown to bind specifically to a synthetic oligoribonucleotide having the 3' splice site sequence of the human beta-globin intervening sequence 1, which includes the sequence UUAGG. Proteins in this fraction were further identified by two-dimensional gel electrophoresis as D01, D02, D1*, and E0; intriguingly, these members of the hnRNP D and E groups are nuclear proteins that are not stably associated with hnRNP complexes. These studies establish the binding specificities of these D and E hnRNPs. Furthermore, they suggest the possibility that these hnRNPs could perhaps bind to chromosome telomeres, in addition to having a role in pre-mRNA metabolism.

[A case of pulmonary malignant fibrous histiocytoma in which cytokines exhibited high value by subculture]

A case of pulmonary malignant fibrous histiocytoma (PMFH) was experienced, and the tumor was subcultured in nude mice. Tumor cells were resected and cultured in medium containing RPMI 1640 and 10% FCS. As a result, in both the nude mice and in the cytokines, as supernatant in the tumorous cells, cultured using ELISA method or RIA method. IL-1 alpha, beta, TNF-alpha, GM-CSF, and in particular IL-6 and G-CSF, exhibited markedly raised values. Clinically, the leukocyte and platelet counts on admission showed markedly elevated values of 27,500/mm3 and 48.3 x 10(4)/mm3, respectively, and the erythrocyte sedimentation rate was increased of 67 mm in 1 hour. These findings corresponded to the physiological findings of elevated IL-6 and G-CSF levels. We have experienced two further patients with PMFH, in whom serum levels of IL-6 and G-CSF were markedly elevated. Some reports have been published on cytokine-generating tumors, but there is no report about cytokine generation in PMFH. We report this patient's very interesting clinical course, together with elevation of cytokine generation.