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P Plevani

Publications and source records attributed to P Plevani.

At least 55 records · Page 3Linked to original sources
PubMed1985

Polypeptide structure of DNA primase from a yeast DNA polymerase-primase complex.

An immunoaffinity chromatographic procedure was developed to purify DNA polymerase-DNA primase complex from crude soluble extracts of yeast cells. The immunoabsorbent column is made of mouse monoclonal antibody to yeast DNA polymerase I covalently linked to Protein A-Sepharose. Purification of the complex involves binding of the complex to the immunoabsorbent column and elution with concentrated MgCl2 solutions. After rebinding to the monoclonal antibody column free primase activity is selectively eluted with a lower concentration of MgCl2. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate showed the presence of five major peptides, p180, p140, p74, p58, and p48 in the immunoaffinity-purified DNA polymerase-DNA primase complex. Free primase and free polymerase fractions obtained by fractionation on the immunoabsorbent column were analyzed on activity gels and immunoblots. These analyses showed that p180 and p140 are DNA polymerase peptides. Two polypeptides of 58 and 48 kDa co-fractionated with the free yeast DNA primase. From sucrose gradient analysis we estimate a molecular weight of 110 kDa for the native DNA primase.

Centrifugation, Density Gradient↗
PubMed1985

Initiation, elongation and pausing of in vitro DNA synthesis catalyzed by immunopurified yeast DNA primase: DNA polymerase complex.

Yeast DNA primase and DNA polymerase I can be purified by immunoaffinity chromatography as a multipeptide complex which can then be resolved into its functional components and further reassembled in vitro. Isolated DNA primase synthesizes oligonucleotides of a preferred length of 9-10 nucleotides and multiples thereof on a poly(dT) template. In vitro reconstitution of the DNA primase:DNA polymerase complex allows the synthesis of long DNA chains covalently linked to RNA initiators shorter than those synthesized by DNA primase alone. The SS (single-stranded) circular DNA of phage M13mp9 can also be replicated by the DNA primase:DNA polymerase complex. Priming by DNA primase occurs at multiple sites and the initiators are utilized by the DNA polymerase moiety of the complex, so that almost all the SS template is converted into duplex form. The rate of DNA synthesis catalyzed by isolated yeast DNA polymerase I on the M13mp9 template is not constant and is characterized by distinct pausing sites, which partly correlate with secondary structures on the template DNA. Thus, replication of M13mp9 SS DNA with the native primase:polymerase complex gives rise to a series of DNA chains with significantly uniform termini specified by the primase start sites and the polymerase stop sites.

Chromatography, Affinity↗
PubMed1985

Identification of the yeast DNA polymerase I gene with antibody probes.

Partially overlapping fragments of the gene encoding yeast DNA polymerase I have been cloned by immunological screening of a yeast genomic library constructed in the phage lambda expression vector lambda gt11. The three gene fragments we analyzed in detail encode part of a yeast protein that has been identified as yeast DNA polymerase I, because it shares with this enzyme a number of antigenic determinants. In fact, the yeast protein fragments expressed by the recombinant phages react with both polyclonal and monoclonal antibodies raised against different, highly purified preparations of DNA polymerase I. Moreover, they can be used to affinity purify antibodies specifically reacting with active DNA polymerase I polypeptides and they compete with the yeast enzyme for binding to antibodies that inhibit catalytic activity. The gene is located on chromosome XIV in the yeast genome, and it is transcribed as a 5.2 kb mRNA.

Antibodies, Monoclonal↗
PubMed1984

DNA polymerase I and DNA primase complex in yeast.

Chromatographic analysis of poly(dT) replication activity in fresh yeast extracts showed that the activities required co-fractionate with the yeast DNA polymerase I. Since poly(dT) replication requires both a primase and a DNA polymerase, the results of the fractionation studies suggest that these two enzymes might exist as a complex in the yeast extract. Sucrose gradient analysis of concentrated purified yeast DNA polymerase I preparations demonstrates that the yeast DNA polymerase I does sediment as a complex with DNA primase activity. Two DNA polymerase I peptides estimated at 78,000 and 140,000 Da were found in the complex that were absent from the primase-free DNA polymerase fraction. Rabbit anti-yeast DNA polymerase I antibody inhibits DNA polymerase I but not DNA primase although rabbit antibodies are shown to remove DNA primase activity from solution by binding to the complex. Mouse monoclonal antibody to yeast DNA polymerase I binds to free yeast DNA polymerase I as well as the complex, but not to the free DNA primase activity. These results suggest that these two activities exist as a complex and reside on the different polypeptides. Replication of poly(dT) and single-stranded circular phage DNA by yeast DNA polymerase I and primase requires ATP and dNTPs. The size of the primer produced is 8 to 9 nucleotides in the presence of dNTPs and somewhat larger in the absence of dNTPs. Aphidicolin, an inhibitor of yeast DNA polymerase I, is not inhibitory to the yeast DNA primase activity. The primase activity is inhibited by adenosine 5'-(3-thio)tri-phosphate but not by alpha-amanitin. The association of yeast DNA polymerase I and yeast DNA primase can be demonstrated directly by isolation of the complex on a column containing yeast DNA polymerase I mouse monoclonal antibody covalently linked to Protein A-Sepharose. Both DNA polymerase I and DNA primase activities are retained by the column and can be eluted with 3.5 M MgCl2. Part of the primase activity can be dissociated from DNA polymerase on the column with 1 M MgCl2 and this free primase activity can be detected as poly(dT) replication activity in the presence of Escherichia coli polymerase I.

Animals↗
PubMed1983

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.

Aphidicolin↗
PubMed1983

Purification and characterization of yeast topoisomerase I.

Yeast topoisomerase I (Mr = 76,000) has been purified to 80% homogeneity using a combination of ion exchange, gel filtration, and DNA-cellulose chromatography. The enzyme was characterized with respect to its ability to relax supercoiled DNA and to catenate nicked circular DNA. Yeast topoisomerase I will remove both positive and negative turns in DNA supercoils in the absence of ATP and magnesium ion. The products of the catenating activity of the enzyme were examined on agarose gels and in the electron microscope. These analyses indicate that yeast topoisomerase I will generate large catenated DNA networks which appear to rearrange to multimeric linear structures upon long incubation time.

DNA Topoisomerases, Type I↗
PubMed1983

Acquisition of deoxyguanosine resistance by TPA-induced T lymphoid lines.

The human leukemic T cell line 8402, which contains terminal deoxynucleotidyl transferase (TdT) and phenotypically resembles precursor thymocytes, when exposed to the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) undergoes in vitro T maturation. TdT disappears from virtually all the cells and a fraction of TdT- -cells express specific T surface markers, such as the T3 determinant. Like T lymphocytes from the thymus, 8402 cells are extremely sensitive to the cytotoxic effect of deoxyguanosine (dGuo). As a consequence of TPA treatment, resistance to dGuo is observed in 8402, as well as in two other TdT+ lymphoid T cell lines, Molt-4 and CEM-10. These results suggest the occurrence of changes in deoxynucleoside metabolism in TPA-treated cells related to the in vitro maturation process. Maturation of 8402 cells, once started, progresses in the presence of additional physiologic stimuli provided by conditioned medium from lymphocyte culture, because a portion of cells display the T8+/T4- phenotype characteristic of cytotoxic/suppressor T cells. This in vitro lymphoid system may thus be used to study the relationships of molecular differentiation between precursor thymocytes and cytotoxic/suppressor T cells.

Animals↗
PubMed1982

Proteolytic degradation of calf thymus terminal deoxynucleotidyl transferase.

A high molecular weight preparation of terminal transferase containing 58,000- and 44,000-dalton peptides has been purified from calf thymus glands. The relationship of these terminal transferase peptides to the low molecular weight form was established with an immunoblot procedure using rabbit antibody directed against the homogeneous calf thymus low molecular weight terminal transferase (32,000 daltons). The 58,000- and 44,000-dalton enzyme species are each shown to be enzymatically active by renaturation in situ after electrophoresis on polyacrylamide gel in the presence of sodium dodecyl sulfate. These results suggest that the homogeneous terminal transferase previously described is derived from the higher molecular weight species by proteolysis during fractionation. Controlled degradation of the high molecular weight calf thymus terminal transferase with trypsin produces fully active enzyme containing alpha- and beta-peptides similar to those found in the 32,000-dalton species. Isoelectric focusing experiments show a decrease of isoelectric pH of the enzyme with proteolysis.

Animals↗
PubMed1982

Active polypeptide fragments common to prokaryotic, eukaryotic, and mitochondrial DNA polymerases.

With a procedure that allows the renaturation of the DNA polymerase catalytic activity in situ after SDS-polyacrylamide gel electrophoresis, we have compared the active polypeptides present in extracts from organisms covering a wide evolutionary range from prokaryotes to eukaryotes, namely: Escherichia coli, Oryza sativa, Daucus carota , Neurospora crassa, Dictyostelium discoideum, Saccharomyces cerevisiae, Ceratitis capitata, Leucophaea maderae , Xenopus laevis, rat tissues and human lymphoblastoid cells. Two main clusters of active peptides are visible in mammalian and adult insect tissues, characterized by a mol. wt. greater than 70000 and less than 50000, respectively. High mol. wt. peptides are heterogeneous in size and correspond to active fragments of DNA polymerase alpha, whereas low mol. wt. peptides show the same migration rate as purified DNA polymerase beta and are not generated by proteolysis of the high mol. wt. cluster, In the three species of fungi studied, only high mol. wt. peptides are found. The same is true in plant cells, where no DNA polymerase beta activity is detectable and the pattern of the high mol. wt. cluster is similar to that observed in E. coli extracts (which also lack low mol. wt. peptides). Also in mitochondria from higher and lower eukaryotes only high mol. wt. species are observed, and the active band(s) range from 70000 to 145000 daltons. Our results indicate that the structure of DNA polymerase has been highly conserved during evolution so that an active fragment of mol. wt. greater than or equal to 70 000 is always found in prokaryotic enzymes and in the replicative species of eukaryotic and mitochondrial DNA polymerases; at a certain stage in evolution, another species of low mol. wt. DNA polymerase (beta or beta-like) appears.

Animals↗
PubMed1982

Clinical relevance of terminal transferase and adenosine deaminase in leukemia.

Terminal Transferase (TdT), Adenosine Deaminase (ADA), immunological membrane markers, cytochemical reactivity and cytogenetics were analyzed in 226 patients with ALL, AUL and AML, in 70 patients with CML and in 3 cases of Ph' positive acute leukemia presenting as ALL. TdT was tested in peripheral blood and bone marrow with both the biochemical and immunofluorescence (IF) methods, and ADA was determined biochemically only in peripheral blood cells. By using conventional cytochemistry, cell surface markers determinations, TdT and ADA analysis, three distinct groups are recognized in ALL at presentation: T-ALL with TdT+ and very high ADA values; non-T, non-B ALL with TdT+ and intermediate levels of ADA; B-ALL with TdT absence and low levels of ADA. Clinical presentation and responses to therapy in adult and children ALL were correlated to TdT determinations. The median survivals in adults, calculated for TdT+ and TdT- groups, were 14.2 and 5.6 months, respectively. TdT and ADA were determined in ALL during remission. The wide fluctuation observed for TdT IF and ADA values prevented a reliable monitoring of remissions. At relapse, TdT and ADA values were similar to those found for ALL at presentation; TdT IF determinations were diagnostic in cases showing CNS involvement as the only localization. Forty per cent of AUL and 11% of AML cases were positive for TdT; the medians of ADA values of the TdT+ cases in both AML and AUL were several times higher than those obtained in the TdT- group. While TdT positivity and high ADA had a favorable prognostic value in AUL, similar conclusions can not be drawn at the moment for AML. In chronic phase of CML, TdT was strictly negative and ADA values were increased over the control line only in cases showing initial signs of transformation. In acute phase, the cases positive for TdT (32%) presented a significantly higher ADA activity than the TdT negative ones. The actuarial survival curves for the TdT+ and TdT- groups differ significantly, presenting median survivals from onset of phase of 11 and 4.8 months respectively. The three cases of Ph' positive ALL were all TdT+, presented high ADA values and entered chronic phase of CML after therapy.

Acute Disease↗
PubMed1982

Evolutionary conservation of DNA polymerase beta structure.

An immunological procedure that uses antiserum against homogeneous calf thymus DNA polymerase beta to detect immunoreactive peptides on NaDodSO4/polyacrylamide gel electrophoresis demonstrates a high degree of conservation of protein sequence and molecular weight for this enzyme, from parastic protozoans to man. By renaturation of DNA polymerase activity in situ after electrophoresis, the enzymatically active peptides are shown to correspond to the immunoreactive peptides. The persistence of sequence and molecular weight for the catalytic peptide of DNA polymerase beta through eons of evolutionary time suggests an essential role for this enzyme in DNA metabolism of complex cells.

Animals↗
PubMed1981

DNA synthesis catalyzed in vitro by yeast extracts.

A procedure to prepare crude extracts from single colonies of Saccharomyces cerevisiae is described. Partially purified extracts catalyzed DNA synthesis directed by single-stranded fd DNA. Maximum activity requires the presence of ribonucleoside triphosphates although extensive DNA synthesis is observed in the presence of only deoxynucleoside triphosphates. Alkaline sucrose gradient analysis demonstrated that initiation of new DNA chains occurs in vitro and the DNA products synthesized are heterogeneous in size, Isopycnic analysis of the products of ribonucleotide-initiated fd DNA replication showed covalent linkage between the initiator RNA and the newly synthesized DNA. The fd-replicating capacity of extracts prepared from cell-division-cycle mutants, defective in events controlling DNA initiation of elongation, showed an increased thermosensitivity in the DNA replication reaction in vitro.

Centrifugation, Density Gradient↗