Biomedical subjects

L Tikhomirova

Publications and source records attributed to L Tikhomirova.

3 recordsLinked to original sources

PubMed1980

Complementation of T4 phage am mutations by hybrid phages lambda-T4.

EcoRI fragments of the T4 cytosine-containing DNA (dC-DNA) were cloned in the lambda XIII vector phage carrying the only restriction site for EcoRI in the repressor gene of lambda. 38 genes of T4 were identified in the cloned fragments by means of marker rescue technique. All cloned early genes and some late genes of T4 were able to complement a corresponding am mutations of T4 phage when nonpermissive cells of E.coli were simultaneously infected with hybrid phages lambda-T4 and am mutants of T4. An average burst size for am mutants from su- cells (when complemented by corresponding hybrid phage) was 20-70 pfu for early genes and 1-3 to 20 pfu for late ones. When the extract of cells infected with hybrid phage lambda-T4-22 containing T4 genes 57, 1, 2, 64 was mixed with the extract of cells infected with T4N51 mutant, the complementation in vitro was observed. So, it was shown that normal product of late gene 2 is synthesized in the cells infected with hybrid phage lambda-T4-22 in the absence of positive regulators of transcription coded by early T4 genes.

Bacteriophage lambda↗

PubMed1980

Functional analysis of hybrid plasmids carrying genes for lambda site-specific recombination.

A number of hybrid plasmids, carrying lambda genes involved in site-specific integrative recombination, have been constructed in vitro. Analysis of protein synthesis in Escherichia coli minicells has shown that Int protein is synthesized only when int gene is expressed constitutively. The plasmids RSF2124::lambda-CD, RSF2124::lambda-Cint-c57, and pInt lambda were able to integrate into the chromosome of E.coli at the attB. The integration of hybrid plasmids into the genome of bacteria has also been shown for polA1 strains restricting the autonomous replication of ColE1 type plasmids. Genetic markers of hybrid plasmids are maintained in polA1 bacteria for at least 50 generations under nonselective conditions. The Southern blotting experiments using [32P]pBR322 DNA and EcoRI fragments of E. coli polA1 chromosome carrying integrated plasmid pInt lambda demonstrated that in this strain hybrid plasmids can be observed only when integrated into the attB of the chromosome according to Campbell's model of integration. In the cells, where autonomous replication of plasmids is possible, they can be observed both in extrachromosomal and integrated states. The integration of the ColE1 replication origin into the chromosome of bacteria is not lethal for the cells. Only attP and the int gene of lambda are necessary for the integration of hybrid plasmids under conditions of effective int gene expression. If the level of Int protein synthesis is high enough, the prophage excision can be observed in the absence of Xis product. The six-fold decrease of Int protein concentration in the cell (in case of pInt lambda 2 as compared to pInt lambda 1) is critical both for integration and excision.

Bacteriophage lambda↗

PubMed1978

Construction of recombinant plasmid carrying the lambda DNA fragment responsible for prophage integration.

The recombinant DNA molecules were constructed from plasmid RSF2124 and the EcoRI fragment of lambda DNA containing the genes responsible for prophage integration. The presence of these genes in recombinant plasmids was detected genetically. lambda int-gene was shown to be expressed in either orientation of insertion in the plasmid. We found that recombinant plasmid was able to integrate into chromosome of lambda lysogens. The integration of plasmid into host chromosome was demonstrated by contransduction of chromosome and plasmid markers using generalized transducer P1 and by specialized transduction with lambda phages.

Coliphages↗