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Biomedical subjects

P P Pumpen

Publications and source records attributed to P P Pumpen.

At least 19 recordsLinked to original sources
PubMed1987

[Genetic transformation of somatic cells. XIV. Expression of gene coding for the human hepatitis B virus surface antigen in mammalian cells].

A set of recombinant plasmids with a gene encoding surface antigen of hepatitis B virus (HBsAg) is constructed. The plasmids were transfected by DEAE-dextran method into different lines of cultured cells and transient expression of the HBsAg gene was studied. The results indicate that: transcriptional enhancer of hepatitis B virus situated downstream from HBsAg gene is active in green monkey kidney cells (CVI), promoter of 5 LTR of bovine leukemia virus is trans-activated in the goat or calf cells infected with BLV. The results are discussed in the light of hypothesis on the role of transcriptional enhancers in determination of tissue-specificity of hepatitis B virus.

Animals↗
PubMed1980

[Bacteriophage MS2 mutants with disrupted phage replicase repressor activity].

A number of ts-mutants with altered characteristics of RNA synthesis in non-suppressor cells at elevated temperatures have been obtained after HNO2-treatment of phage MS2am623 (amber mutation in site 50). The mutant ts130 is studied in detail: its peak of RNA synthesis is displaced 10 min. later and the total amount of RNA is reduced in 5-10 times. No RNA synthesis is observed in ts130-infected cell at 46 degrees C. Changes in the character of RNA synthesis are accompanied by the over-production of phage subunit of replicase: at 42 degrees C the replicase/RNA ratio in ts130 is 20 times higher than that of the original phage MS2am623. It is assumed that there is a decrease in the activity of replicase--RNA repressor complex in ts130 resulting in the loss of replicase control over its own synthesis while the control of coat protein synthesis remains unaffected.

Coliphages↗
PubMed1978

[Regulation of RNA replication in RNA-containing bacteriphages. RNA synthesis in coat protein polar mutants].

The synthesis of RNA by polar coat protein mutants f2sus3 and Qbetaam12 under suppressor (Escherichia coli S26R1E, Su+-1; H12R8a Su+-3) and non-suppressor (E. coli AB259; S26) conditions was examined. It was demonstrated that the synthesis of viral RNA under non-suppressor conditions in the presence of rifamycin produced the same gaussian pattern of rates as the synthesis of RNA by wild type phage or non-polar coat protein mutants. However, the total amount of RNA was decreased approximately 10-fold and the peak of RNA synthesis was displaced 7--10 min later. The number of infective centers was reduced also 10-fold indicating that a certain time-lapse was required to overcome the polarity of the parental RNA, this process being of single occurrence, exclusively on the parental RNA, but not on the progeny strains. As a consequence, it was concluded that the initiation of translation at the replicase cistron starts on the nascent RNA chains within the replicative complexes and not on the fully-synthesized templates with their complete secondary structure. The data obtained are not in contradiction with the hypothesis concerning the role of the repressor complex II (replicase-RNA) to slow down the synthesis of replicase and RNA in the coat protein mutants. The polarity can not be responsible probably for the blocking of the replicase cistron on the nascent chain following the block of coat protein cistron. Therefore, it appears appropriate to assume the existence of two binding sites for the replicase as repressor which is in keeping with the conclusions of Weissmann and co-workers.

Coliphages↗
PubMedDate not supplied

[Exposure of the major immunodominant epitope of the gp51 envelope protein of bovine leukosis virus on the surface of the hepatitis B core antigen capsid].

Insertion of 48 amino acid long sequence of envelope protein gp51 of bovine leukemia virus (BLV), located from position 56 till 103 of mature protein, into Pro144 position of hepatitis B core antigen (HBcAg) leads to the formation of chimeric capsids. These capsids preserve morphology of intact HBcAg but expose on their outer surface BLV epitopes which are localised in the inserted gp51 fragment and responsible for the recognition of chimeras by monoclonal anti-gp51 antibodies MAK14. The anti-genicity of gp51 epitopes within chimeric capsids is not disturbed after shortening of C terminal part of inserted gp51 fragment by deletion of amino acids 73-103. The resulting chimeras show the same capsid-forming ability as well as HBcAg and gp51 antigenic properties.

Amino Acid Sequence↗
PubMedDate not supplied

[Structure and expression of human hepatitis B virus surface antigen].

In view of the growing occurrence rate of the virus-induced hepatitis B and also of the special role played by this particular virus (HBV) in the application of recombinant genetic techniques to the study of complex biological systems, an attempt was made to survey the available evidence concerning the widely investigated and practically the most important part of the viral genome, viz. the gene coding for the surface antigen (HBsAg) and the protein itself. The possible antigenic structure of the protein was investigated using data on the primary structure of 11 cloned HBsAg gene variants and on the synthesis of peptides simulating its immunological properties. Special emphasis was placed on quantitative assessment of antigenicity and immunogenicity. Expression of the gene in homologous systems was studied using cultures of eukaryotic tissues: both as part of HBV nucleotide sequences incorporated into the chromosome and as part of extrachromosomal DNA. The latest findings on HBsAg gene expression in yeast and bacteria are reviewed.

Bacteria↗
PubMedDate not supplied

[The comparative mapping of virion and cloned DNA of the hepatitis B virus].

The entire hepatitis B virus (HBV) genome and its fragments have been cloned into the BamHI site of the plasmid pBR322 vector. The identity of physical maps of cloned and authentic virion DNAs was demonstrated by restriction enzyme analysis. The location of restriction sites is suggestive of a certain similarity between the studied HBV DNA and HBV DNA, subtype ayw (Galibert et al., 1979). From the restriction enzyme analysis of virion DNA repaired and 32P-labeled by the endogenous DNA-polymerase reaction, the new information concerning the location and maximal length (approximately 1500 nucleotides) of the single-stranded region of HBV DNA has been established.

Base Sequence↗
PubMedDate not supplied

[Subjection of tetracycline resistance genes to cat promotor gene in plasmid pBR325].

A series of plasmids with tetracycline resistance genes (Tcr-operon) subjected to transcription from chloramphenicol acetyl transferase promoter (Cmr-promoter) have been constructed on the basis of plasmid pBR325, AprCmrTcr. For this purpose, a 0.8 Md fragment in pBR325 DNA bordered by unique EcoRI and HindIII restriction sites was cut out and structural genes of Tcr-operon were fused to the cat gene nucleotides corresponding to Cmr-promoter and first 72 amino acids of cat (alton, Vapnek, 1979; Marcoli et al., 1980). These plasmids with molecular weight amounting to 3 Md confer AprTcr phenotype to host cells. Tetracycline resistance can be eliminated completely by the deletion of a) Cmr-promoter; b) part of the first Tcr-operon gene.

Acetyltransferases↗