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P Plevani

Publications and source records attributed to P Plevani.

64 records · Page 4Linked to original sources
PubMed1980

Purification and characterization of two forms of DNA-dependent ATPase from yeast.

Two forms of DNA-dependent ATPase activity have been purified from yeast extracts. The two ATPases differ from each other in chromatographic properties and heat stabilities but have similar molecular weight and reaction properties. DNA-dependent ATPase I has been purified to near homogeneity, while DNA-dependent ATPase II is only partially purified. The two ATPases from yeast are related structurally since antiserum raised against ATPase I cross-react against ATPase II. Yeast DNA-dependent ATPase I has a native molecular weight of about 68,000 and consists of a single polypeptide chain. ATPase II also sediments on sucrose gradient as a 68,000-dalton protein. Both yeast DNA-dependent ATPases hydrolyze dNTPs and rNTPs to their corresponding nucleoside diphosphates and orthophosphate, but dATP and ATP are preferred substrates. In addition to nucleoside triphosphates, both enzymes require a divalent cation and a polynucleotide for activity. Single-stranded DNAs and polydeoxynucleotides are the most effective co-substrates for yeast DNA-dependent ATPases. Addition of yeast DNA-dependent ATPases to DNA synthesis system containing yeast DNA polymerases does not significantly stimulate the rate of DNA synthesis.

Adenosine Triphosphatases↗
PubMed1980

Characterization of Bacillus subtilis mutants temperature-sensitive in the synthesis of ribonucleic acid.

Two mutants of Bacillus subtilis temperature-sensitive in RNA synthesis were isolated. One mutation (rna-20) was demonstrated to be an allele of a previously identified gene (Riva et al., 1976). The other mutation (rna-16) identified a different gene and was mapped near aroI. The rna-16 mutation at the permissive temperature affected the spore outgrowth process. Purified RNA polymerase from rna-16 did not show any temperature sensitivity or structural defect.

Bacillus subtilis↗
PubMed1980

Effect and mechanism of action of aphidicolin on yeast deoxyribonucleic acid polymerases.

The antibiotic aphidicolin inhibited in vitro deoxyribonucleic acid synthesis catalyzed by crude yeast extracts and by partially purified yeast deoxyribonucleic acid polymerases. The mechanism of action of aphidicolin on yeast deoxyribonucleic acid polymerase I was noncompetitive with deoxyguanosine 5'-triphosphate, deoxyadenosine 5'-triphosphate, and deoxythymidine 5'-triphosphate and was of the mixed type with deoxycytidine 5'-triphosphate. The relative ratio of enzyme to the template-initiator complex was important for detecting the inhibitory effect of the antibiotic. The inhibition of in vitro deoxyribonucleic acid synthesis by aphidicolin was reversible, and the effect on yeast deoxyribonucleic acid polymerase might have been partially mediated by some supplementary factor(s).

Anti-Bacterial Agents↗
PubMed1978

Initiation of enzymatic DNA synthesis by yeast RNA polymerase I.

In vitro DNA synthesis by yeast DNA polymerase I can be initiated by partially purified yeast RNA polymerases in the presence or absence of rNTPs. Homogeneous yeast RNA polymerase I initiates DNA synthesis by yeast DNA polymerase I on single-stranded DNA templates only in the presence of all four rNTPs. A protein capable of initiating enzymatic DNA synthesis on single-stranded DNA in the absence of rNTPs has also been separated from partially purified yeast RNA polymerase I fractions. Analysis of the RNA polymerase I initiated replication products of phage fd DNA on alkaline sucrose gradients showed noncovalent linkage between the newly synthesized DNA and the template. Isopycnic analyses of the ribonucleotide initiated fd DNA replication products demonstrated covalent linkage between the initiator RNA and newly synthesized DNA. Results from 32P-transfer experiments confirmed the covalent linkage between RNA and DNA chains and showed the presence of all four ribo- and deoxyribonucleotides at the RNA--DNA junctions. The ribonucleotide found most frequently at the RNA--DNA junction is uridylate and the purine deoxynucleotides occur more frequently than pyrimidine deoxynucleotides.

DNA↗
PubMed1977

Enzymatic initiation of DNA synthesis by yeast DNA polymerases.

Partially purified yeast RNA polymerases (RNA nucleotidyltransferases) initiate DNA synthesis by yeast DNA polymerase (DNA nucleotidyltransferase) I and to a lesser extent yeast DNA polymerase II in the replication of single-stranded DNA. The enzymatic initiation of DNA synthesis on phage fd DNA template occurs with dNTPs alone and is further stimulated by the presence of rNTPs in DNA polymerase I reactions. The presence of rNTPs has no effect on the RNA polymerase initiation of the DNA polymerase II reaction. RNA polymerases I and III are more efficient in initiation of DNA synthesis than RNA polymerase II. Analyses of the products of fd DNA replication show noncovalent linkage between the newly synthesized DNA and the template DNA, and covalent linkage between the newly synthesized RNA and DNA.

Amanitins↗
PubMed1976

Synthesis of RNA and protein in a mutant of Bacillus subtilis temperature sensitive during spore germination.

Bacillus subtilis strain PB 2427 temperature sensitive in the synthesis of RNA during spore germination and outgrowth has been characterized to some extent. At non permissive temperature (46 degrees C) strain PB 2427 synthesizes stable and unstable RNA for 50 min from the beginning of germination and then stops. Most of the stable RNA is degraded to shorter molecules but can be identified as ribosomal RNA by hybridization-competition experiments. At non permissive temperature, in the presence of chloramphenicol, synthesis of RNA proceeds, though at a reduced rate, for at least 90 min. By hybridization-competition experiments it can also be shown that the RNA synthesized at 46 degrees C in the presence of chloramphenicol includes transcripts that are absent, from the RNA synthesized at 46 degrees C in the absence of drug. The RNA polymerase (holo and core) purified from vegatative cells of the mutant strain does not appear to have a greater heat-lability as compared with the enzyme purified from the parental strain. At non permissive temperature only six polypeptide chains with MW ranging from 47,000 to 78,000 daltons are synthesized by the germinating spores of the mutant.

Bacillus subtilis↗
PubMed1975

In vivo and in vitro effects of rifampicin and streptolydigin on transcription of Kluyveromyces lactis in the presence of nystatin.

Rifampicin and streptolydigin, if used in conjunction with nystatin, depress the growth of Kluyveromyces lactis. The incorporation of labeled leucine into protein is inhibited by nystatin whereas the incorporation of labeled uracil into RNA is inhibited by rifampicin in nystatin-treated cells. In order to study the mechanism of inhibition of RNA synthesis we purified by DEAE-Sephadex column chromatography four forms of RNA polymerase from K.lactis cells. The general properties of these enyzmes are similar to those of Saccharomyces cerevisiae and of other eukaryotic RNA polymerases. In particular, enzymes IA, IB and III are more active with poly[d(A-T)] template and Mn-2+ than with native or denatured calf thymus DNA. Enzyme II shows optimal activity with denatured calf thymus DNA and Mn2+. When challenged with native calf thymus DNA all enzymes prefer Mg-2+ as a divalent cation whereas with denatured calf thymus DNA all enzymes are more active with Mn-2+. Enzyme II is inhibited by lambda-amanitin but no enzyme is sensitive to rifampicin and streptolydigin. The inhibition of growth and uracil uptake observed when rifampicin is added to nystatin treated cells is probably not caused by a specific inhibition of transcription.

Anti-Bacterial Agents↗
PubMedDate not supplied

Method and parameters for genetic transformation of Streptococcus sanguis Challis.

A simple procedure for genetic transformation of Streptococcus sanguis Challis was developed and standardized. During the exponential phase of growth, cells became competent while growing as diplococci in broth containing 10% foetal calf serum. High levels of competence were maintained by the cultures for 60 min. Competent cells could be stored frozen without loss of competence for at least three years. Using total chromosomal DNA as donor, the dose-response curve for transformation of a point mutation (streptomycin resistance) showed one-hit kinetics, as the DNA concentration varied from 0.000001 to 10 micrograms/ml. At 10 micrograms/ml, more than 2.2% of the colony-forming units were transformed to streptomycin resistance, while transforming activity remained detectable with 1 pg of DNA/ml. Optimal time of exposure of competent cells to transforming DNA was 30 min. The transformation reaction was inhibited at 0 and 4 degrees C, whereas it occurred efficiently both at 25 and 37 degrees C.

DNA, Bacterial↗
PubMedDate not supplied

S-phase DNA damage checkpoint in budding yeast.

Eukaryotic cells must be able to coordinate DNA repair, replication and cell cycle progression in response to DNA damage. A failure to activate the checkpoints which delay the cell cycle in response to internal and external cues and to repair the DNA lesions results in an increase in genetic instability and cancer predisposition. The use of the yeast Saccharomyces cerevisiae has been invaluable in isolating many of the genes required for the DNA damage response, although the molecular mechanisms which couple this regulatory pathway to different DNA transactions are still largely unknown. In analogy with prokaryotes, we propose that DNA strand breaks, caused by genotoxic agents or by replication-related lesions, trigger a replication coupled repair mechanism, dependent upon recombination, which is induced by the checkpoint acting during S-phase.

DNA Damage↗