[Immunocytochemical characterization of the DNA-polymerase alpha-positive colonic mucosal epithelial cells in patients with ulcerative colitis]

Colonic mucosal epithelial cells (EpC) in patients with ulcerative colitis (UC) have been shown to express HLA-DR antigen. In the present study, we observed the characteristics of HLA-DR-positive EpC using immunoperoxidase technique. In the control group, colonic EpC expressed HLA-ABC, but not HLA-DR. Only the EpC at the base of glands revealed positive for DNA-polymerase alpha (DNA-P). On the other hand, in actively inflamed mucosa of UC, about 80% of glands strongly expressed HLA-DR. Furthermore, most of EpC in the HLA-DR-positive glands showed positive nuclear stainings for DNA-P. This indicates that these EpC are not in the resting stage. It is strongly suggested that there are close relationships between the regeneration or proliferation of the EpC and class II MHC (HLA-DR) expression on the EpC in UC.

Intracellular localisation of a subunit of human DNA polymerase alpha affecting primase activity recognised by monoclonal antibody (HDR-854-E4) and its application to distinction between proliferative and non-proliferative lesions

We have successfully established one murine hybridoma that secretes a monoclonal antibody specific for the 77,000 subunit of human DNA polymerase alpha. The results of immunochemical studies, using HDR-854-E4 monoclonal antibody (MAb) and immunoperoxidase detection methods, demonstrate intranuclear and intracytoplasmic localisation of the subunit in all the human culture cell lines tested. The immunoperoxidase reaction product exhibits a diffuse pattern of distribution within the cytoplasm and nucleoplasm, but nucleoli are clearly negative. In cultured cell lines, HeLa and KATO III, more than 95% of the cells are positive, suggesting that the subunit antigens persist throughout the mitotic cycle. No subunit antigen was recognised in resting mononuclear cells (MNC). Immuno-electron microscopic examination of HeLa cells confirms and extends these observations. We have further examined the expression level of the subunit antigen in various normal and cancerous tissues. Strong reaction was observed in proliferating normal and cancer cells such as cancer cells from the gastrointestinal (GI) tract, thyroid, malignant lymphoma, breast, cells in the germinal centres of lymph nodes, epithelial cells in the GI tract and nephrogenic zones in fetal kidney. Finally, we utilised this antibody as a diagnostic tool in biopsies of the thyroid and GI tract. Thyroid cancer was stained positively with this antibody, while follicular adenoma was not. Gastric cancer was stained strongly and adenomatous polyp and hyperplastic polyp were stained moderately. This antibody is not only specific and powerful for application of a novel approach to the complex biochemical mechanisms of mammalian DNA replication, but also useful for distinction between proliferative and non-proliferative lesions.

[Diagnosis and treatment of endometrial hyperplasia]

Endometrial hyperplasia (EH) was found to coexist in 13 of 21 patients (cystic glandular hyperplasia, 13; adenomatous hyperplasia, 9) with endometrial adenocarcinoma (EC), but in only 44 of 940 patients with other than EC. In this study, blood type (A, B, H), c-myc translation products, estrogen receptor and DNA polymerase alpha were examined on endometrium of proliferative phase (EPP), EH and EC. Patient blood type products were shown in EH surrounding EC, and yet they were detected in only small portion or none of EC itself. H products were detected in EC of other than O type. c-myc translation products were shown in only a small portion of cancer cells. EPP had many ER positive cells and a few proliferating cells as they were shown by staining with anti-DNA polymerase alpha monoclonal antibody. EC can be divided into two types, one has few ER positive cells and many proliferating cells, other many ER positive cells and a few proliferating cells. In EH, the numbers of ER positive cells and DNA polymerase alpha positive cells were between those of EPP and EC. In a patient with atypical hyperplasia, high dose Medroxyprogesterone acetate (MPA) therapy induced that stratification and papillary growth of gland lining epithelia disappeared, and that cytoplasmic enlargement and vacuolation appeared. These findings were important histopathological changes in high dose MPA administration to EH and EC.

[Purification and characterization of DNA-dependent DNA-polymerase alpha from human placenta]

A preparation of human placenta DNA polymerase with specific activity 6000 unit/mg was obtained. The protocol of the enzyme purification includes the crude extract preparation, the subsequent chromatographies on phosphocellulose, red sepharose, DEAE sepharose and hydroxylapatite. The isolated DNA polymerase belongs to alpha-type according to the large molecular mass (greater than 150 kDa), high sensitivity to N-ethylmaleimide, the profound inhibition of DNA polymerization activity by 200 mM KCl and the ability to catalyze DNA synthesis, using the deoxyribonucleic template and ribonucleic primer. The DNA polymerase preparations contain a few forms with Stokes radii 50-60 A and sedimentation coefficients 7.3-9.0 S as found from data of gel-filtration and ultracentrifugation in glycerol density gradient, accordingly. The existence of four various forms of DNA polymerase activity: 150, 170, 220, 480 kDa were revealed by native electrophoresis. The four steps of purification result in DNA polymerase preparation that was shown by electrophoresis to contain 15-20% of protein possessing the polymerase activity. However the preparation obtained seems to be a "chromatographically pure substance", according to following ion-exchange and affinity chromatographies. The other proteins without polymerase activity are suggested to be the components of the replicative complex of human placenta cells.

Proliferative cell index in endometrial adenocarcinoma of different nuclear grades

Proliferative cell indices (PCI) in 20 cases of endometrial adenocarcinoma were obtained by staining DNA polymerase alpha. The PCI ranged from 11.1 to 42.1, averaging 24.7 +/- 8.7. Four cases of stage III all exhibited fairly large PCI (30.4-32.9). In contrast, in 16 cases of stage I the values were spread over a wide range. In 13 cases with histological grade (HG) 1 of stage I, larger PCI were obtained in the nuclear grade (NG) 2 group; the mean PCI values of HG 1-NG 1 and HG 1-NG 2 were 16.5 +/- 4.6 and 25.6 +/- 5.2, respectively. Because of the good correlation between PCI and HG or NG, PCI may be useful as an additional prognostic factor in endometrial adenocarcinoma, especially in stage I cases.

[Experimental study on the effect of UFT with concomitant radiotherapy of uterine cervical cancer]

In order to examine effectiveness of the chemotherapy with concomitant radiotherapy, an experimental study was designed using AMCC-1 cell line established from a human uterine cervical carcinoma in our laboratory. The growth of AMCC-1 cells cultured in plastic flask was inhibited significantly in the group treated with a half of minimal effective doses of 60Co and 5-FU in comparison with the control group. The 5-FU treatment after radiation inhibited the AMCC-1 cell growth more effectively than that before radiation. The growth of AMCC-1 tumor transplanted into nude mice was inhibited significantly in the group given a combination chemoradiotherapy, consisted of oral administration of three quarters of minimal effective dose of UFT for fourteen consecutive days and radiation of a half of minimal effective dose of 60Co. The oral administration of UFT after radiation inhibited the AMCC-1 tumor growth more effectively than that before radiation. These results suggest that the radiotherapy with administration of UFT was more effective against uterine cervical cancer than radiation alone and it is important to administer UFT orally after radiation as well as before radiation.

Calcium-dependent calmodulin-binding proteins associated with mammalian DNA polymerase alpha

Complex, multiprotein forms of bovine (calf thymus), hamster (Chinese hamster ovary cell), and human (HeLa) cell DNA polymerase alpha (Pol alpha) were analyzed for their content of calmodulin-binding proteins. The approach used an established autoradiographic technique employing 125I-labeled calmodulin to probe proteins in denaturing SDS-polyacrylamide gel electropherograms. All three Pol alpha enzymes were associated with discrete, Ca2+-dependent calmodulin-binding proteins. Conventionally purified calf thymus Pol alpha holoenzyme contained three prominent, trifluoperazine-sensitive species with apparent molecular masses of approx. 120, 80 and 48 kDa. The 120 and 48 kDa species remained associated with the polymerase.primase core of the calf enzyme during immunopurification with monoclonal antibodies directed specifically against the polymerase subunit. The patterns of the calmodulin-binding proteins displayed by conventionally purified preparations of hamster and human Pol alpha enzymes were similar to each other and distinctly different from the pattern of comparable preparations of calf thymus Pol alpha. Immunopurified preparations of the human and hamster Pol alphas retained significant calmodulin-binding activity of apparent molecular masses of approx. 55, 80 and 150-200 kDa.

Analysis of butylphenyl-guanine, butylphenyl-deoxyguanosine, and butylphenyl-deoxyguanosine triphosphate inhibition of DNA replication and ultraviolet-induced DNA repair synthesis using permeable human fibroblasts

The purine base and nucleoside analogues N2-(p-n-butylphenyl)-guanine (BuPh-Gua) and N2-(p-n-butylphenyl)-2'-deoxyguanosine (BuPh-dGuo) are strong inhibitors of isolated mammalian DNA polymerase alpha, but are less potent that expected as inhibitors of DNA replication in intact cultured cells [G. E. Wright, L. W. Dudycz, Z. Kazimierczuk, N. C. Brown and N. N. Khan, J. med. Chem. 30, 109 (1987)]. The mechanistic basis for these observations was explored using permeable human fibroblasts. DNA replication in the permeable cells was inhibited only slightly by BuPh-Gua and BuPh-dGuo at 100 microM, the highest concentration which could be attained. Similar results were obtained for ultraviolet-induced DNA repair synthesis, a process which is though to involve the same DNA polymerase as replication. More detailed studies were performed using the corresponding nucleotide analogue, N2-(p-n-butylphenyl)-2'-deoxyguanosine-5'-triphosphate (BuPh-dGTP), which is much more water-soluble than the base and nucleoside. The apparent Ki values for BuPh-dGTP inhibition of both replication and ultraviolet-induced repair synthesis in permeable cells were approximately 3 microM. These values are several hundred-fold greater than the apparent Ki for BuPh-dGTP inhibition of isolated human DNA polymerase alpha, which is approximately 10 nM. We conclude that BuPh-Gua and BuPh-dGuo are poor inhibitors of DNA replication in intact cells not because of permeability barriers, but because, unlike polymerase alpha, cellular DNA synthesis is relatively insensitive to this group of inhibitors. These results suggest that polymerase alpha may not be a good general model for predicting the potency of base, deoxyribonucleoside and deoxyribonucleotide analogues as inhibitors of mammalian cellular DNA replication. The fact that the permeable cell systems accurately reflect the relative insensitivity to butylphenyl-guanine derivatives of mammalian DNA replication suggests that permeable cells may be useful tools in future studies of base and nucleoside analogues.

Identification and subcellular localization of the polypeptide for chick DNA primase with a specific monoclonal antibody

Polypeptides responsible for activities of chick embryo DNA primase and DNA polymerase alpha were identified using monoclonal antibodies specific to these two enzymes. The 4-8H antibody neutralized DNA polymerase alpha activity measured on activated DNA template and also ribonucleoside triphosphate-dependent DNA synthesis on single-stranded DNA template (DNA primase-DNA polymerase alpha combined activity) to a partial extent (about 30%), but did not affect DNA primase activity. The 4-2D antibody, although it did not affect DNA polymerase alpha activity, did neutralize both DNA primase activity and DNA primase-DNA polymerase alpha combined activity extensively (up to 70%). Immunoblotting analysis of the DNA primase-DNA polymerase alpha complex showed that 4-2D and 4-8H antibodies recognize 60-kDa and 160-180-kDa polypeptides, respectively. An immunoaffinity column made of either of these antibodies retained DNA primase-DNA polymerase alpha complex. When the enzyme was eluted from the 4-8H column with alkaline solution, DNA primase was eluted prior to DNA polymerase alpha. In the case of 4-2D antibody column chromatography, the elution order of two enzymes was reversed. Results indicate that two enzymes in the complex which was retained in the antibody column were dissociated by lower alkaline pH than that dissociated the antigenic enzymes from the corresponding antibodies. In both cases, the fractions with DNA primase activity contained exclusively 60-kDa polypeptide, while those with DNA polymerase alpha contained 160-180-kDa polypeptides. Thus, DNA primase resided in 60-kDa polypeptide and was recognized by 4-2D antibody while DNA polymerase alpha resided in 160-180-kDa polypeptides and was recognized by 4-8H antibody. Immunofluorescence made with the DNA primase-specific 4-2D antibody as well as with 4-8H antibody appeared in granular structures which were tightly bound to the nuclear matrix. These nuclear fluorescences were much reduced in quiescent cells. Furthermore, since the fluorescence made by these antibodies was induced by adding serum to the quiescent cells in serum-deprived cultures, the expression of DNA primase and its organization in the structures on the nuclear matrix are regulated in correlation to the proliferating stage of cells, as observed with DNA polymerase alpha.

Immunochemical detection of a primase activity related subunit of DNA polymerase alpha from human and mouse cells using the monoclonal antibody

A hybrid cell line (HDR-854-E4) secreting monoclonal antibody (E4 antibody) against a subunit of human DNA polymerase alpha was established by immunizing mice with DNA replicase complex (DNA polymerase alpha-primase complex) prepared from HeLa cells. The E4 antibody immunoprecipitates DNA replicase complex from both human and mouse cells. The E4 antibody neutralizes the primase activity as assessed either by the direct primase assay (incorporation of [alpha-32P]AMP) or by assay of DNA polymerase activity coupled with the primase activity using unprimed poly(dT) as a template. The E4 antibody does not neutralize DNA polymerase alpha activity with the activated calf thymus DNA as a template. Western immunoblotting analysis shows that the E4 antibody binds to a polypeptide of 77 kilodaltons (kDa) which is tightly associated with DNA polymerase alpha. The 77-kDa polypeptide was distinguished from the catalytic subunit (160 and 180 kDa) for DNA synthesis which was detected by another monoclonal antibody, HDR-863-A5. Furthermore, it is unlikely that the 77-kDa peptide is the primase, since we found that the E4 antibody also immunoprecipitates the mouse 7.3S DNA polymerase alpha which has no primase activity, and Western immunoblotting analysis shows that the 77-kDa polypeptide is a subunit of the 7.3S DNA polymerase alpha. Furthermore, after dissociation of the primase from mouse DNA replicase by chromatography on a hydroxyapatite column in the presence of dimethyl sulfoxide and ethylene glycol, the 77-kDa polypeptide is associated with DNA polymerase alpha, and not with the primase.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of chromosome aberrations induced by incubation at a restrictive temperature in the mouse temperature-sensitive mutant tsFT20 strain containing heat-labile DNA polymerase alpha

tsFT20 cells derived from a mouse mammary carcinoma cell line, FM3A, which has temperature-sensitive DNA polymerase alpha activity (Y. Murakami, H. Yasuda, H. Miyazawa, F. Hanaoka, and M. Yamada, Proc. Natl. Acad. Sci. USA, 82:1761-1765, 1985) were rapidly committed to death after temperature upshift to 39 degrees C. tsFT20 cells synchronized in S phase were more sensitive to the restrictive temperature than exponentially growing cells. In order to gain insight into the processes from the interruption of DNA synthesis to cell death, we analyzed chromosome aberrations induced in tsFT20 cells which had been incubated for 2 or 4 h at the restrictive temperature and then cultured at the permissive temperature. The majority of metaphase cells showed extensive chromosome aberrations such as chromatid gaps, breaks, and exchanges; chromosome pulverizations; their mixed types; and ring chromosomes. Analyses with the use of cell synchronization and autoradiography revealed that chromosome aberrations were induced only in the cells which synthesized DNA during incubation at 39 degrees C. We classified the chromosome aberrations into five types: gap or break type; exchange type; pulverization type; complex type; and ring type. The temporal order of the appearance of these types of chromosome aberrations was found to be the above described order. It was further found that cycloheximide dramatically repressed the induction of chromosome aberrations, and metaphases with many chromosome aberrations exhibited a large number of sister chromatid exchanges. These results indicate that abnormal cessation of DNA replication in tsFT20 cells at the restrictive temperature due to the inactivation of DNA polymerase alpha results in cell death via induction of double-strand breaks which lead to chromosome aberrations as well as sister chromatid exchanges.

[Comparison of the effectiveness of the interaction of ribo- and deoxyriboprimers with DNA-polymerase from the human placenta]

The Km and Vmax values for primers d(pA)n, d(pT)n, r(pA)n, r(pU)n where n = 1-16, were compared. The Km values for minimal primers dTMP, dAMP, rUMP, rAMP were found to be 48, 71, 602 and 602 microM, respectively. The Vmax value for any NMP made up approximately 7% of that for (pN)10. The lengthening of any primer per one mononucleotide unit for n from 1 to 10 resulted in the decrease of the Km value 1.8-fold and the increase of the Vmax value 1.35-fold. The ratios of the Km values for primers r(pA)n-d(pA)n and r(pU)n-d(pT)n were 7.5 and 12.5, respectively, for any n. The Km value for [d[pT)8]r(pU) primer was the same as for r(pU)9, but not for d(pT)9. Decanucleotide [d(Tp)9]ddT interacted with the polymerase competitively to the template, but not to the primer. The primer's 3'-OH group was supposed to form the hydrogen bond with the enzyme. The absence of 3'-hydroxygroup in [d(Tp)9]ddT resulted in its inability to compete effectively with the primer. The difference of the affinity of ribo- and deoxyriboprimers is due, apparently, to the existence of the different conformation of the furanose rings in the ribose and deoxyribose.

Phenotyping of proliferating lymphocytes in angioimmunoblastic lymphadenopathy and related lesions by the double immunoenzymatic staining technique

Biopsy specimens of lymph nodes with the histologic characteristics of angioimmunoblastic lymphadenopathy with dysproteinemia (AILD) were obtained from 9 cases (4 cases of AILD and 5 cases of AILD-like T lymphoma [AILD-T]) and histologically analyzed by the use of a double immunoenzymatic staining technique with the combination of a monoclonal antibody against lymphocyte membrane antigen and that against human DNA polymerase alpha (pol alpha), which is detectable in the nucleus of the cells in G1, S, and G2 phases. In all 9 cases, the pol alpha + proliferating cells had a peripheral T-cell phenotype with T11 and Leu-4 antigens, whereas proliferating B cells with B1 antigen were rarely observed. As for T-cell subset antigens, the proliferating T cells had T4+ helper/inducer phenotype in 7 cases, while T8+ suppressor/killer T cells proliferated in 2 cases, although a significant number of T4+ proliferating cells were also recognized. The study on malignant lymphomas that evolved in the 2 cases showed that the T-subset antigens on major proliferating tumor cells were the same as those found in the preceding AILD lesions, suggesting that lymphoma T cells originate from the AILD lesion. The results suggested that AILD without histologic manifestations of malignancy and AILD-T may be a neoplastic disease derived from either subset of peripheral T cells.

2',5'-oligoadenylate synthetase activity in human mammary tumors and its potential correlation with tumor growth or hormonal responsiveness

Since interferon inducible 2',5'-oligoadenylate (2,5An) synthetase activity is present in a wide variety of cells and is affected by various hormonal conditions, primary human mammary tumor extracts were examined for the constitutive presence of this enzyme and its possible relationship with the various hormonal receptor levels in these tissues. Further, since 2,5An synthetase has been implicated as a possible factor controlling cell replication, we assayed DNA polymerases in these same tumor extracts to determine any correlation between 2,5An synthetase activity and growth potential. A survey of the soluble extracts from 24 different surgically removed human mammary tumor specimens for 2,5An synthetase activity indicated that this enzyme was indeed present in all extracts but in widely varying amounts of activity (31-2,666 nmol adenosine 5'-phosphate incorporated/mg protein). The 2,5An synthesized in the enzymic reactions ranged in size from di- to hexamers, with trimers being the abundant 2,5An in the majority of tumors. A comparison of the assay results for estrogen and progestin receptors with 2,5An synthesis indicated that high 2,5An synthetase activity was found in both estrogen or progestin positive and negative tumors. Thus, 2,5An synthetase activity was unrelated (r = 0.329 and 0.077, respectively, for estrogen and progestin receptors) to the hormonal receptor content of these tumors. A similar comparison was made between 2,5An synthesis and assay results for the activities of DNA polymerase alpha, regarded as the principal DNA replicating enzyme, and DNA polymerase beta, regarded as the DNA repair enzyme. Although the activity of the polymerases were also quite varied, the majority of tumor extracts demonstrated higher alpha polymerase activity with no parallel difference between the alpha and beta enzymes. There was, however, a weak correlation (r = 0.751) between 2,5An synthetase activity and DNA polymerase alpha activity among the tumors examined. Less of a correlation existed with DNA polymerase beta activity (r = 0.600). These results suggested that the potential of the tumors to synthesize 2,5An was unrelated to their hormonal responsiveness and only weakly related to their growth potential reflected by DNA polymerase alpha activity.

Cloning and expression of a cDNA encoding a catalytically active fragment of calf thymus DNA polymerase alpha

A calf thymus cDNA expression library was constructed in the EcoRI site of lambda gt11 and probed with an antibody raised against calf thymus DNA polymerase alpha. Three classes of antibody-reactive clones were isolated. The largest class carried a 1.9 kilobase calf cDNA insert and expressed a 165-175 kilodalton beta-galactosidase:calf fusion protein which displayed DNA polymerase activity. The characteristic responses of the polymerase activity to alpha-specific inhibitors and antibodies identified the 1.9 kilobase cDNA as a sequence specifically derived from the structural gene encoding the pol alpha catalytic core.

Preferential binding of DNA primase to the nuclear matrix in HeLa cells

Studies of the spatial organization of DNA replication have provided increasing evidence of the importance of the nuclear matrix. We have previously reported a relationship between rates of DNA synthesis and the differential binding of DNA polymerase alpha to the nuclear matrix over the S-phase. We now report the detection of DNA primase bound to the HeLa nuclear matrix. Matrix-bound primase was measured both indirectly, by the incorporation of [32P]dAMP into an unprimed single-stranded template, poly(dT), and directly, by the incorporation of [3H]AMP into matrix DNA. Characteristics of this system include a requirement for ATP, inhibition by adenosine 5'-O-(thiotriphosphate), a primase inhibitor, and insensitivity to aphidicolin and alpha-amanitine, inhibitors of polymerase alpha and RNA polymerase, respectively. Subcellular quantification of primase and polymerase alpha activity revealed that while most (approximately 72%) primase activity is bound to the matrix, only a minority (approximately 32%) of polymerase alpha activity is matrix-bound. Treatment of the nuclear matrix with beta-D-octylglucoside allowed the solubilization of approximately 54% of primase activity and approximately 39% of the polymerase alpha activity. This data provides further evidence of a structural and functional role for the nuclear matrix in DNA replication. The ability to solubilize matrix-bound replicative enzymes may prove to be an important tool in the elucidation of the spatial organization of DNA replication.

A multiprotein form of DNA polymerase alpha from HeLa cells. Resolution of its associated catalytic activities

The majority of the DNA polymerase alpha activity in HeLa cells has been isolated and purified as a multiprotein Mr 640,000 form. The multiprotein form of DNA polymerase alpha corresponds to DNA polymerase alpha 2 that was previously reported by us (Lamothe, P., Baril, B., Chi, A., Lee, L., and Baril, E. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 4723-4727). The highly purified DNA polymerase alpha 2 has in addition to DNA polymerase alpha-associated DNase, primase, and diadenosine 5',5"'-P1,P4-tetraphosphate (Ap4A)binding activities and accessory primer recognition proteins C1 and C2. The DNA polymerase alpha and associated activities increase coordinately during the G1/S-phase transition of the cell cycle. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the electrophoretically homogeneous DNA polymerase alpha shows that it is composed of at least eight polypeptides in the molecular weight range of 180,000-15,000. Hydrophobic chromatography on butyl-agarose resolves the DNase and Ap4A-binding protein from a complex of DNA polymerase alpha, primase, and the primer recognition proteins C1 and C2. Hydrophobic chromatography of the latter complex on phenyl-Sepharose resolves the C1 protein from a DNA polymerase alpha-C2 protein-primase complex. Phosphocellulose chromatography of the DNA polymerase-primase-C2 protein complex resolves the C2 protein from a complex of DNA polymerase alpha-primase.

Dissociation of thymidylate biosynthesis from DNA biosynthesis by 5-fluoro-2'-deoxyuridine and 5,8-dideazaisofolic acid

The effects of 5-fluoro-2'-deoxyuridine (FdUrd) and 5,8-dideazaisofolic acid on the coordination of thymidylate synthase activity and DNA synthesis were examined in human CCRF-CEM leukemic cells following a continuous exposure to these agents. In logarithmically growing control tumor cells, the rate of in situ thymidylate synthase activity equaled the rate of DNA synthesis. However, in tumor cells incubated with growth-inhibitory concentrations of either FdUrd or 5,8-dideazaisofolic acid for 48 h, the rate of thymidylate synthase activity was between 15- and 17-fold greater than the rate of DNA synthesis. The loss in tumor cell viability of FdUrd-treated cells was temporally related to this prolonged dissociation of thymidylate biosynthesis from DNA biosynthesis. The dissociation of thymidylate from DNA biosynthesis in cells incubated with FdUrd was not closely related to thymidylate depletion. The intracellular concentrations and activities of thymidylate synthase were comparable in tumor cells incubated for 24 or 48 h with either a growth-inhibitory or non-growth-inhibitory concentration of FdUrd, indicating no direct relationship among these parameters. Indirect thymidylate depletion induced by the combination of 2,4-diamino-5-(3',4'-dichlorophenyl)-6-methylpyrimidine, hypoxanthine, and glycine inhibited in situ thymidylate synthase activity and DNA synthesis to an equal extent. In addition, the intracellular concentrations of all four deoxyribonucleoside 5'-triphosphates in tumor cells incubated with FdUrd for 48 h were between 1.3- and 3.1-fold greater than their respective concentrations in control cells, reflecting their decreased utilization in DNA synthesis in FdUrd-treated cells. These data indicated that inhibition of CCRF-CEM cell growth and DNA synthesis following a continuous exposure to cytostatic concentrations of either FdUrd or 5,8-dideazaisofolic acid resulted primarily from interference with thymidylate incorporation into DNA, and not simple blockade of thymidylate synthase.

Size difference in catalytic polypeptides of two active forms of mouse DNA polymerase alpha and separation of the primase subunit from one form, DNA replicase

There are two active forms of DNA polymerase alpha in mouse cells. One form (DNA replicase) is a DNA polymerase associated with primase activity and the other form (7.3 S polymerase) has no primase activity (Yaugar, T., Kozu, T. and Seno, T. (1982) J. Biol. Chem. 257, 11121-11127). The primase activity was dissociated from partially purified DNA replicase by hydroxyapatite column chromatography in buffer containing dimethyl sulfoxide and ethylene glycol. Nearly homogeneous primase, consisting of a 58 kDa polypeptide was obtained by glycerol gradient sedimentation and DEAE-cellulose column chromatography. Experiments on the effect of proteinase treatment and measurement of the molecular weight of the catalytic polypeptide of DNA replicase after its dissociation from the primase polypeptide indicated that the primase is not part of the DNA polymerase molecule, but an independent protein associated with DNA polymerase alpha, and that the latter is a 115 kDa catalytic polypeptide. The other form of DNA polymerase alpha, 7.3 S polymerase, consists of a 72 kDa catalytic polypeptide. Thus, the two forms of mouse DNA polymerase alpha have partially, if not completely, different catalytic polypeptide structures, suggesting that the 7.3 S polymerase is not simply formed from DNA replicase by dissociation of the primase subunit.

[DNA-polymerase alpha from human placenta. Effectiveness of interaction between oligothymidylates of different lengths and the template-binding site]

Modification of human placenta DNA polymerase alpha by (pT)2pC[Pt2 + (NH3)2OH].(pT)7 was investigated. The linear time dependence of the enzyme activity logarithm suggested a pseudo-first order for modification. Kd value of enzyme-affinity reagent complex (0.5 microM) was estimated. The enzyme inactivation by the affinity reagent and protection from inactivation in the presence of oligonucleotides of varying length were used for determining Kd values of the enzyme-ligand complexes. Oligonucleotide d(pT)2pC(pT)7 (Kd 0.15 microM), d(Tp)9T (Kd 0.15 microM) and [d(Tp)9]ddT (Kd 0.15 microM) protected the enzyme from inactivation with equal efficiency. The protective action of oligothymidylates d(Tp)nT (where n changes from 3 to 14) strongly depended on the chain length, the Kd values diminishing from 5.3 to 0.0091 microM in the geometrical progression. The addition of one link to the oligothymidylate chain resulted in 1.71-fold increase in the oligonucleotide affinity for the enzyme specific site. Such a change corresponds to Gibbs energy change of about 0.32 kcal/mole. It is supposed that the monomer units of pentadecathymidylate (at least beginning with the third one) in d(Tp)14T-enzyme complex form neither hydrogen bonds nor electrostatic linkages with the enzyme. Kd values of oligonucleotides as templates are shown to reflect quite well the true affinity of template for the enzyme. This affinity increases in the presence of a primer. However, the ratio of the affinity for different oligonucleotides does not change in the presence or absence of a complementary primer.

Studies of DNA polymerases alpha and beta from cultured human cells in various replicative states

DNA polymerase activities from HeLa cells and from cultured diploid human fibroblasts in various growth states were compared. alpha-Polymerase activities from log phase fibroblasts treated with sodium butyrate and from stationary phase HeLa cells had DEAE-cellulose elution patterns that differed from those of polymerases from dividing cells. Moreover, alpha- and beta-polymerases from nondividing cells replicated synthetic polymers less faithfully. Although similar changes were observed previously for polymerases from late-passage and postconfluent early passage fibroblasts, amounts of alpha-polymerase activity recovered from nondividing cells in this study did not dramatically decline as they had in the former cases. The alpha-polymerase activities from HeLa cells and fibroblasts in various growth states sedimented near 7.5S in 0.4 M KCI and could be inhibited by a monoclonal IgG fraction prepared against KB cell alpha-polymerase. By several criteria, there was no significant differences in levels of UV-stimulated repair synthesis observed in early or late-passage postconfluent fibroblasts or in log phase fibroblasts treated with sodium butyrate. In summary, levels of alpha-polymerase do not necessarily correlate either with replicative activity or with apparent levels of repair synthesis. However, cells with decreased replicative activity always yielded enzyme with decreased fidelity in vitro and altered chromatographic behavior. It appears, therefore, that the alterations observed for alpha-polymerase from late-passage cells may be attributed more generally to the nondividing nature of these cells.

Proliferative activity of human solid tumors evaluated by thymidine labeling index and primer-dependent alpha-DNA polymerase

Proliferating cells, independent of their position in the cell cycle, contain a primer-dependent alpha-DNA polymerase (PDP); we have, therefore, tested the feasibility of the PDP assay in breast, ovarian, and head and neck tumors. Experimental results demonstrate that the PDP labeling index (PDP-LI) is constantly superior to the thymidine labeling index (TLI), which indicates the percentage of S phase cells. The PDP-LI/TLI ratios observed were 5.0 in breast cancer, 3.6 in ovarian cancer, and 2.5 in head and neck tumors. Higher PDP-LI scores have been obtained in metastatic breast tumor samples (PDP-LI = 8.8) compared to nonmetastatic tumors (PDP-LI = 4.9).

Estrogen induced expansion of the growth fraction in receptor negative human breast cancer

The feasibility of a cytokinetic chemotherapy based on estrogenic recruitment has been evaluated in 5 patients, affected by locally advanced breast cancer with low or absent receptor content. Tumor proliferative activity was evaluated by the thymidine labeling index (TLI) and the primer-dependent alpha DNA polymerase assay (PDP-LI) which gives an in vitro estimation of tumor growth fraction. The patients have been treated with diethylstilbestrol (DES) 1 mg/die. for 3 days, followed by FAC (5-Fluorouracil 600 mg/m2, Adriamycin 50 mg/m2, Cytoxan 600 mg/m2) i.v. on day 4 q. 21 days. Radical surgery was performed after 3 DES-FAC regimens. Tumor biopsies for evaluation of tumor proliferative activity were performed immediately before and after DES and 24 h after chemotherapy. Our results demonstrate that DES was able to induce an increase in TLI in 3/5 of the patients while the PDP-LI was significantly increased in 5/5 of the patients; subsequent chemotherapy induced a sharp decrease in tumor proliferation. These results provide the rationale for the design of cytokinetic regimens where chemotherapy is administered at the time of estrogen induced tumor cell recruitment.

Quantification of lymphocyte activation by measurement of DNA polymerase alpha activity

Measurement of the activity of the enzyme DNA polymerase alpha has been investigated with regard to its potential usefulness as a method for the detection and quantification of lymphocyte activation in vivo. A modified enzyme assay was developed in order to optimise measurement of activity in crude homogenates of cells or tissues, thus allowing the convenient handling of multiple samples. Specificity of the assay for polymerase alpha was ensured by the inclusion in the assay mixture of dideoxythymidine triphosphate, an inhibitor of the other eukaryotic DNA polymerases. The activity of DNA polymerase alpha was found to be closely correlated with [3H]thymidine incorporation in a mitogen-stimulated in vitro system. The usefulness of the polymerase alpha method for the quantification of lymphocyte activation was validated in 3 different in vivo systems of either immune-mediated or drug-induced lymphoid cell response.

Relation between enzymatic activities and the degree of malignancy of human lymphomas

The relationship between the intracellular levels of DNA polymerase alpha (DP-alpha), adenosine deaminase (ADA) and lactate dehydrogenase (LDH) and the degree of malignancy of human lymphomas was investigated. Twelve non-neoplastic lymph nodes and 88 malignant lymphomas were examined. For non-Hodgkin's lymphomas (NHL) the low or high grade of malignancy was established according to three classifications: the Rappaport, the Kiel and the Working Formulation for Clinical Usage, with the latter also recognizing an intermediate grade group. Non-neoplastic lymph nodes had significantly lower levels of all the three enzymes than those found in high-grade malignant NHL (the P value ranged from less than 0.02 to less than 0.001). Hodgkin's disease, a slowly evolving neoplasia, showed lower levels of DP-alpha (P less than 0.001) and ADA (P less than 0.001), but not of LDH, than high-grade NHL. Among NHL, whatever classification was used, the low-grade malignant lymphomas had significantly lower levels than the high-grade ones for all the three enzymes (P less than 0.005 or P less than 0.001). The intermediate-grade group of the Working Formulation differed from the high-grade group for DP-alpha (P less than 0.01) and ADA (P less than 0.02) but not for LDH. It differed from the low-grade group only for ADA (P less than 0.005). Lymphoblastic and Burkitt's lymphomas were the groups with the highest levels of the three enzymes. Among low-grade lymphomas very low values were found in the histological entities defined as DLWD in the Rappaport classification, CLL and lymphoplasmacytoid immunocytoma in the Kiel classification and small lymphocytic (group A) in the WF. The levels of all enzymes in these histotypes were always significantly different from the other low-grade histotypes, and from the intermediate-grade ones of the WF. In the Kiel classification polymorphous lymphoplasmacytoid lymphoma, recently recognized as a group with a quite aggressive clinical course, was characterized by high levels of all three enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

Mouse DNA polymerase alpha-primase terminates and reinitiates DNA synthesis 2-14 nucleotides upstream of C2A1-2(C2-3/T2) sequences on a minute virus of mice DNA template

The distribution of termination and initiation sites in a 5081-nucleotide minute virus of mice DNA template being copied by a highly purified mouse DNA polymerase alpha-DNA primase complex in the presence of GTP has been examined. The 3'-hydroxyl termini (17 in all) were clustered at six sites that were located 2-14 nucleotides upstream of C2A2C2, C2AC3, or C2A2T2 sequences. When either [alpha-32P]- or [gamma-32P]GTP was included in the DNA polymerase reaction mixtures, nascent DNA became radiolabeled. Analysis of the 32P-labeled material following treatment of the DNA with tobacco acid pyrophosphatase, bacterial alkaline phosphatase, or ribonuclease T1 revealed the presence of oligoribonucleotide chains averaging 5-7 nucleotides long and beginning with 5' GTP residues. Eight presumptive DNA primase initiation sites were located opposite C4 or C5 sequences 3-9 nucleotides upstream of one of the three closely related hexanucleotides C2A2C2, C2AC3, and C2A2T2. RNA-DNA junctions were found 3-10 nucleotides downstream of DNA primase initiation sites. The results indicate that hexanucleotides having the general formula C2A1-2(C2-3/T2), herein referred to as psi, are involved in promoting termination of DNA synthesis and/or de novo initiation of RNA-primed DNA chains by DNA polymerase alpha-primase.

Delayed and reduced cell replication and diminishing levels of DNA polymerase-alpha in regenerating liver of aging mice

Kinetics of cell replication was compared in regenerating livers of Mus musculus at ages ranging between 6 and 32 months. Incorporation of [3H]-thymidine into DNA and autoradiographic analysis showed that the maximal extent of DNA replication following partial hepatectomy became delayed with age. Furthermore, the total fraction of parenchymal and nonparenchymal cells in S phase at different intervals during regeneration diminished as mice aged. The specific activity of DNA polymerase-alpha, the putative replicative enzyme, declined progressively during aging. The specific activity of DNA polymerase-beta, the purported repair enzyme, declined to an appreciably lesser extent during the lifespan of the mouse. No evidence was found for the appearance of a specific inhibitor of polymerase-alpha in senescent mouse liver. Also, the bulk of the activities of both hepatic DNA polymerase-alpha and -beta remained localized in the cell nucleus throughout the lifetime of the animal and were mainly associated with chromatin.

Immunocytochemical localization of chick DNA polymerases alpha and beta +

An immunofluorescent method using specific antibodies was employed to detect DNA polymerases alpha and beta in chick cells. With monoclonal antibodies produced by four independent hybridoma clones, most of the DNA polymerase alpha was shown to be present in nuclei of cultured chick embryonic cells. With a polyclonal, but highly specific, antibody against DNA polymerase beta, this enzyme was also shown to be present in nuclei. DNA polymerase alpha was detected in proliferating cells before cell contact and in lesser amount in resting cells after cell contact, indicating that its content is closely correlated with cell proliferation. On the other hand, similar amounts of DNA polymerase beta were detected in proliferating and resting cells. Furthermore, DNA polymerase beta was detected in nuclei of most cells, while DNA polymerase alpha was detected only in large round nuclei in seminiferous tubules of chick testis. DNA polymerase alpha is presumably present in cells that are capable of DNA replication, and during the cell cycle it seems to remain in the nuclei during the G1, S, and G2 phases, but to leave from condensed chromatin for the cytoplasm during the mitotic phase.

Polypeptide structure of DNA polymerase I from Saccharomyces cerevisiae

DNA polymerase I of the yeast Saccharomyces cerevisiae has been purified to near homogeneity. The enzyme sediments under high salt conditions as a band at 7.4 S and two polypeptides of Mr = 140,000 and 110,000 are resolved by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Both polypeptides react with rabbit anti-yeast DNA polymerase I serum and can be shown to be enzymatically active by renaturation in situ after electrophoresis on polyacrylamide gels in the presence of sodium dodecyl sulfate. This high molecular weight form of yeast DNA polymerase I is very sensitive to inhibition by aphidicolin. The biochemical properties of the enzyme and inhibitors that may aid in distinguishing yeast DNA polymerases I and II are also described.

Probing yeast RNA polymerase A subunits with monospecific antibodies

Monoclonal antibodies were raised in mouse against native RNA polymerase A from Saccharomyces cerevisiae. After screening with the spot-immunodetection technique, 14 hybridomas were selected and the antibodies produced in mice. Their specificity, analyzed by blot-immunodetection, was found to be markedly biased towards a few RNA polymerase subunits: A135 , A49 , A43 , and A14.5. A different monoclonal antibody directed against the largest subunit, A190 , was obtained by immunizing a mouse with RNA polymerase A dissociated into its subunits with SDS. Two antibodies, which probably recognized the same antigenic determinant on subunit A135 , inhibited in vitro RNA synthesis. Inhibition was prevented by preincubation of the enzyme with DNA, suggesting a role for the A135 subunit in template binding. The antibody directed against A14.5 interacted with the A14.5 kd subunit present in all three forms of the yeast nuclear RNA polymerases but did not interfere with RNA polymerase activity. These antibody probes will be useful to study subunit function in reconstituted transcription systems.

Analysis of calf thymus DNA polymerases alpha and beta and terminal deoxynucleotidyl transferase on two-dimensional polyacrylamide gels

Calf thymus DNA polymerases alpha and beta [EC 2.7.7.7] and terminal deoxynucleotidyl transferase [EC 2.7.7.31] were analyzed on two-dimensional gel slabs. DNA polymerase beta appeared as a single spot on two-dimensional gel at the position of 40,000 daltons and pI 8.0 using non-equilibrium pH gradient gel electrophoresis for the first-dimensional run. By overlapping gel slabs, it was possible to identify the distinct spot of DNA polymerase beta among many polypeptide spots of a crude enzyme fraction. 10S DNA polymerase alpha showed two clusters of polypeptide spots on two-dimensional gel slab. One cluster was composed of three large polypeptides of 140,000-150,000 daltons and another was composed of four smaller polypeptides of 46,000-50,000 daltons. All these spots were arranged in a narrow pI range (6.5-6.8) although each spot showed a distinct pI value. Purified terminal deoxynucleotidyl transferase showed three polypeptides of 57,000, 42,000, and 33,000 daltons at similar pI values (7.0-7.2). Each polypeptide consisted of plural spots which differed slightly in pI but were the same in molecular weight. These results suggest a microheterogeneity of polypeptides of terminal deoxynucleotidyl transferase as well as those of 10S DNA polymerase alpha.

Intracellular localization of human DNA polymerase alpha with monoclonal antibodies

We have successfully established 16 stable murine hybridomas that secrete monoclonal antibodies specific for human DNA polymerase alpha. The results of immunocytochemical studies, using 4 of these monoclonal antibodies and immunoperoxidase detection methods, document the exclusively intranuclear localization of DNA polymerase alpha in three separate lines of cultured human cells. By light microscopy, the immunoperoxidase reaction product exhibits a diffuse pattern of distribution within the nucleoplasm, but nucleoli are clearly negative. In cultures of the transformed lines, KB nd BeWo, more than 955 of the cells are positive, suggesting that intranuclear DNA polymerase alpha antigens persist throughout the mitotic cycle. In striking contrast, in the normal diploid fibroblast line, WI-38, a smaller fraction of the cultured cells is positive, and there is no detectable polymerase alpha antigen in the closely apposed cells of microcolonies that are presumed to be contact-arrested and no longer mitotically cycling. In cells in mitosis that have dissolved their nuclear envelopes (and are thus transiently anucleate), the anti-polymerase alpha reaction continues to be strongly positive, and in this single circumstance the reaction product is diffusely distributed throughout the cell cytoplasm. Initial electron microscopic examination of KB cells confirms and extends these observations. The immunoperoxidase reaction product is essentially limited to the nuclear compartment and is predominantly distributed in the midzonal region of the nucleoplasm between centrally disposed nucleoli and peripherally located blocks of condensed chromatin.

Intracellular localization of DNA polymerase alpha

Immunoglobulin (IgG) and the F(ab')2 fragment of IgG were prepared from serum of a rabbit immunized with purified calf thymus DNA polymerase alpha (deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase, EC 2.7.7.7). An indirect immunofluorescent method based on these reagents was used to detect the intracellular localization of DNA polymerase alpha in primary fetal bovine fibroblasts. The results show that the bulk of DNA polymerase alpha is located in the perinuclear region of the cytoplasm. Immunofluorescent staining of cytoplast and Ficoll-Paque gradient-purified karyoplast fragments resulting from cytochalasin enucleation show the presence of DNA polymerase alpha in cytoplasts and the virtual absence of the enzyme in the nucleus of the karyoplast itself. The implication of this unusual intracellular location for DNA polymerase alpha is discussed.

Immunological reagents for comparisons of DNA polymerase-alpha and DNA polymerase-beta

Antibodies to homogeneous calf thymus DNA polymerase-beta and calf thymus DNA polymerase-alpha preparations were raised in rabbits. The antiserum against calf thymus DNA polymerase-beta cross-reacts with all vertebrate DNA polymerase-beta preparations tested, but does not cross-react with trypanosome DNA polymerase-beta, DNA polymerase-gamma, terminal transferase, yeast DNA polymerases, and Escherichia coli DNA polymerase I. The antibodies against calf thymus DNA polymerase-alpha cross-react with DNA polymerase-alpha from mouse, human, and chicken, but do not cross-react with DNA polymerase-alpha from sea urchin embryos and Drosophila embryos, DNA polymerase-beta, DNA polymerase-gamma, terminal transferase, yeast DNA polymerases, and E. coli DNA polymerase I.

DNA polymerases in parasitic protozoans differ from host enzymes

Analysis of extracts of the bloodstream forms of Trypanosoma brucei showed that both DNA polymerase-alpha and DNA polymerase-beta activities were present. The detection of DNA polymerase-beta in T. brucei demonstrates the presence of this enzyme in unicellular organisms. DNA polymerase-beta is present also in Leishmania mexicana. The DNA polymerases in T. brucei are immunologically distinct from the host enzymes. The structural differences between the parasite and the host enzymes could be exploited for the development of agents to combat parasitic diseases.

Neonatal macrosomia in maternal diabetes

In order to determine the effect of maternal diabetes on the somatic growth of the rat fetus and to elucidate mechanisms underlying the control of fetal growth, concentrations of DNA and proteins and DNA polymerase-alpha activities in neonates were examined. The maternal status was classified as normal (no urinary glucose excretion), mildly diabetic (0.01-0.99 g/day urinary glucose), and severely diabetic (1.00 g/day or more urinary glucose). The total DNA contents in mg/neonate were 26.8 +/- 2.2 (mean +/- SEM), 31.3 +/- 2.5, and 29.4 +/- 2.7 for neonates from normal, mildly diabetic and severely diabetic mothers, respectively. The DNA polymerase activities in (cpm/g neonate) X 10(-3) for the same groups of neonates were 432 +/- 58, 1,008 +/- 74, and 888 +/- 118, respectively. These results indicate that the neonatal macrosomia disappears as the severity of maternal diabetes increases. Furthermore, DNA polymerase is one of possible biochemical sites through which macrosomia is manifested in diabetic pregnancies.

Variation of two forms of DNA polymerase-alpha during a HeLa cell cycle

HeLa cells contain two forms of DNA polymerase-alpha (P-I and P-II) with varied affinity to DNA, separable on a DNA-cellulose column. The activity of each form was followed during a cell cycle of synchronized culture of the HeLa cells. P-I was recovered from the nuclear extract and P-II from the cytoplasmic fraction. The P-I activity remained at a low level during M to G1 phase until a marked increase between late G1 and S phases, while P-II activity increased gradually throughout the period. Both activities attained their highest level at mid-S phase and then the P-I activity declined more rapidly than the P-II. Addition of hydroxyurea at mid-S phase inhibited the decrease of both enzyme activities. The enzyme activity of nuclear extract from S phase cells was not inhibited by mixing with extract from M phase cells. When the cytoplasmic fraction from M phase cells was chromatographed on a DNA-cellulose column, single activity peak was observed at the position of P-II. These results suggest that the decrease in P-I activity is neither due to the presence of an inhibitor nor to mere release of the enzyme from chromosomes.

DNA-dependent-DNA-polymerase: possible limiting influence on cell reproduction during viral leukemogenesis

Evidence is presented that during viral leukemogenesis spleen cell nuclei show an increase in labelling index and mean grain count, that is not accompanied by any changes in the nuclear level of DNA-polymerase-alpha. It is suggested that polymerase production remains under the control of the normal cell mechanisms and the virus may affect cell proliferation by altering the primer-template levels.