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Biomedical subjects

I Boros

Publications and source records attributed to I Boros.

At least 55 records · Page 3Linked to original sources
PubMed1986

Expression vectors based on the rac fusion promoter.

The -35 region of the rrnB P2 promoter and the -10 region of the lacZpo promoter-operator were fused to form the strong and regulatable rac promoter. Vectors were constructed that allow the attachment of protein-coding sequences to the beta-galactosidase alpha-peptide (LacZ alpha) in any reading frame. By introducing a high-copy-number mutation, the synthesis of a LacZ alpha-chloramphenicol acetyltransferase fusion protein reached more than 60% of total cell protein in Escherichia coli.

Acetyltransferases↗
PubMed1984

High-copy-number derivatives of the plasmid cloning vector pBR322.

A stable copy-number mutant of a pBR322-derived plasmid was isolated. The mutation was found to be a single G----T transversion located near the 3' end of a DNA segment coding for the regulatory RNA I. The resulting copy number for this plasmid is approx. 1000 per cell or 65% of total cellular DNA. Several cloning vectors have been constructed from this copy-number mutant and their practical application is discussed.

Base Sequence↗
PubMed1983

Identification of two new promoters probably involved in the transcription of a ribosomal RNA gene of Escherichia coli.

The DNA sequence in the region preceding the rrnB gene of Escherichia coli was determined up to the 1821st nucleotide upstream from the beginning of the sequence coding for mature 16 S rRNA. In vitro transcription experiments indicated the presence of two new promoters in this region, located more than 1 kb upstream from the known P1 and P2 promoters of rrnB. Previous electron microscopic studies demonstrated that these sites bind RNA-polymerase very strongly. In vitro transcription, starting at these sites reads through the entire region into the rrnB gene without termination. A similar uninterrupted transcription into rrnB in vivo can be demonstrated by S1-mapping, and by fusing the DNA containing the new promoters (but not P1 and P2) to the lacZ gene. Thus it seems likely that these promoters (P3 and P4) belong functionally to the rrnB gene and play some role in its regulation of expression.

Base Sequence↗
PubMed1983

A novel type of bacterial transcription unit, specifying mRNA, rRNA, and tRNA.

Previously it had been shown that a chromosomal region preceding the rrnB gene of Escherichia coli contains an 867 base pair-long open reading frame and it is co-transcribed with the rrnB gene both in vitro and in vivo. Here we report that minicells programmed by recombinant plasmids carrying this region or a deletion derivative of it, synthetise a protein of the expected size. Thus this transcription unit codes for mRNA, rRNA, and tRNA.

Escherichia coli↗
PubMed1981

[Angioimmunoblastic lymphadenopathy and Hodgkin's disease].

In the lymph node biopsy specimen of a 80 year old male patient with clinical symptoms of malignant lymphoma histologically angioimmunoblastic lymphadenopathy have been diagnosed (AIBLP). In the second biopsy specimen obtained several weeks later histological picture of Hodgkin's disease (Hd) of the mixed cellularity type was found. In the first biopsy specimen micro-Sternberg -Reed-cells (micro-S-R) were also observed. Presence of the latter in the Lennert's type of lymphoma indicate the transformation of the process into Hd. Micro-S-R-cells present in the early stage of Hodgkin's disease reminiscent of AIBLP provide possibility of a correct diagnosis. Authors assume that micro-S-R-cells, as well as S-R-cells of diagnostic value might be destroyed by cytostatic T-lymphocytes.

Aged↗
PubMed1980

RNA-polymerase binding at the promoters of the rRNA genes of Escherichia coli.

The promoter region of two bacterial rRNA genes was investigated by electron-microscopic analysis of polymerase binding, transcription initiation and nitrocellulose filtration of RNA-polymerase-DNA complexes, using restriction endonuclease generated fragments of recombinant plasmids and a transducing phage. The following observations have been made: 1. Two transcription initiation sites have been located approximately 200 and 300 base pairs upstream from the beginning of the sequence coding for mature 16 S rRNA. 2. Polymerase binding at these sites can be observed electronmicroscopically and a 360 base-pair fragment containing these sites binds to nitrocellulose in the presence of RNA-polymerase. This complex dissociates even at moderately high (0.1-0.2 M) salt concentrations. Although transcription initiation is reported to be more frequent at the first of these sites, the binding is much stronger at the second site. 3. In the case of the rrnD gene, BamHI cleaves a few base pairs upstream from the first transcription start site. This cleavage destroys polymerase binding at this site but does not influence binding at the second site. 4. At higher polymerase/DNA ratio four weak but distinct and regularly spaced binding sites can be observed preceding the two initiation sites at approximately 1000, 820, 640 and 440 base pairs before the mature 16 S rRNA sequence. 5. An extremely strong binding site is located about 1300 base pairs upstream from the beginning of the 16 S rRNA sequence. Very little (if any) initiation occurs at this site. The possibility is discussed that the noninitiating binding sites preceding the two transcription start points might functionally belong to the promoter region.

Binding Sites↗
PubMed1980

Staphylococcus aureus and protein A as mitogens for rabbit T lymphocytes.

The thymidine uptake by rabbit lymph nodes, spleen and peripheral blood lymphocytes was stimulated by Protein A (SpA) and SpA-containing staphylococci. The cell fraction enriched in T lymphocytes showed a higher degree of stimulation with SpA than the fraction enriched in B cells. Rabbit thymocytes showed a marked thymidine uptake by treatment with SpA but not with staphylococci. The monovalent fragment B of SpA (reacting with IgG) neither stimulated nor inhibited the incorporation of thymidine in rabbit lymph node lymphocytes indicating that the Fc reacting site of SpA cannot be responsible for the mitogenicity.

Animals↗
PubMed1979

Structure of the promoter region for the rrnB gene in Escherichia coli.

The nucleotide sequence of the promoter region for the rrnB gene of E. coli had been determined by the Maxam-Gilbert technique. The 700 bp long sequence had been compared with the published sequences of four other rRNA promoter regions. The rrnB sequence was found to be homologous with the rrnA promoter sequence till the 370th base upstream from the coding region of mature 16S rRNA. The significance of this homology is discussed and a tentative model is proposed to account for the unusual properties of the rRNA promoters.

Base Sequence↗
PubMed1979

Nucleotide sequence of a secondary attachment site for bacteriophage lambda on the Escherichia coli chromosome.

The nucleotide sequence of a secondary attachment site for bacteriophage lambda was determined in a region near the rrnB gene at 88 min on the E. coli chromosome. The sequence has a 8 base pair interrupted homology GCT TTTTA to the common core of the primary attachment site (attB) and the corresponding phage sequence (attP). The site of crossover during integration lies probably between nucleotides -3 and +1. The flanking regions have no obvious homology to the arms of either attP or attB.

Bacteriophage lambda↗
PubMed1979

Physical map of the seven ribosomal RNA genes of Escherichia coli.

Escherichia coli DNA was digested with restriction endonucleases BamHI, PstI, EcoRI, SalI, HindIII, XhoI, BglII, SmaI, HpaI and with selected double and triple combinations of the same enzymes. The digests were electrophoresed and hybridized with 32P-labelled ribosomal RNA by using the Southern blotting technique. The resulting bands could be arranged into seven groups, and it was possible to construct a unique physical map of the seven rRNA genes (operons) of the bacterial chromosome. Mapping information obtained on several transducing phages and recombinant plasmids carrying rRNA genes, and mapping data published in the literature helped to determine the final map. The results suggest that phage lambda daroE152 carries a "hybrid" rRNA gene which was probably formed by recombination between two different chromosomal rRNA genes.

Chromosome Mapping↗
PubMed1978

Cloning of an E. coli ribosomal RNA gene and its promoter region from lambdarifd18.

The DNA of the specialized transducing phage lambdarifd18, which carries a bacterial rRNA transcription unit, was digested with restriction enzymes EcoRI and/or BamHI. Attempts were made to clone fragments containing the presumed rRNA promoter region or the entire rRNA gene in RSF2124 or pBR313 plasmid vectors with the following results: (1) We failed to clone an EcoRI fragment with the rRNA promoter region in plasmid RSF2124. (2) A smaller EcoRI-BamHI fragment with the rRNA promoter was also unclonable by itself, but one recombinant was found containing this fragment together with another large (7 Mdaltons) fragment, derived from phage lambda. The presence of this large fragment proved to be essential. The identity of these DNA fragments in the recombinant clone was confirmed by redigestion with several restriction enzymes, hybridization with rRNA, and in vitro transcription experiments, which showed preferential rRNA transcription. (3) A BamHI fragment encompassing the entire rRNA gene was easily cloned. Such stable clones carried a doubled number of rRNA genes. In vitro transcription using the recombinant plasmid resulted in 70% rRNA transcription. These recombinant clones allow the easy purification of the relevant DNA fragments for further investigation including sequencing.

Chromosome Mapping↗
PubMed1977

[Significance of the AgHB and of the immune reaction in chronic hepatitis].

The authors studied 496 patients with chronic persistent or aggressive hepatitis, and active or non-active hepatic cirrhosis, and 396 non-hepatic patients. AgHB was detected in the serum by immuno-electrophoresis and by immuno-diffusion and, in the liver, by needle biopsy, using immuno-fluorescence. The liver diagnosis was made histologically. AgHB was found in 34.2% of patients, more often in chronic active hepatitis (53.7%) than in inactive forms (23.2%). This finding may be interpreted as a sign of severity, chronic aggressive hepatitis is more frequently caused by B virus and by its persistence in the liver. In all cases of chronic, aggressive hepatitis studied with AgHB in the serum, AgHB was detected in the nuclei of the liver parenchyma cells. It should be emphasized that there is no significant difference from the immunological point of view, between patients with AgHB and the others, the levels of gamma-globulin and immunoglobulin were higher in the former. The increased frequency of AgHB in the active forms of the disease compared with stabilised forms, reinforces its physiopathological, diagnostic and prognostic significance.

Antibody-Producing Cells↗