[Effect of superhelical DNA on the transcription of cloned genes of the T4 phage].

The effect of DNA superhelicity on the transcription of T4 DNA fragments containing early genes uvs W, Y and late genes 25-29 was studied. RNA polymerase transcribes both early and late phage genes within the supercoiled recombinant plasmid. Late genes relative transcription increases essentially when T4-modified RNA polymerase is used.

[Temperature-sensitive mutant Escherichia coli for the B-subunit of DNA-gyrase. The effect on replication and transcription].

A temperature sensitive mutant affecting the B-subunit of DNA gyrase was isolated. The mutation leads to the thermolability of DNA gyrase in vitro and to the plasmid DNA relaxation in vitro. The immediate stop of the increase in mutant culture titre has been observed under nonpermissive conditions.

[Interactions of subunits of DNA gyrase].

Interaction of DNA gyrase A- and B-subunits during the process of DNA supercoiling was studied. For this purpose a E. coli Cour-1 mutant resistant to coumermycin and containing a mutation in the B-subunit of DNA gyrase was isolated and the influence of the DNA gyrase A-subunit specific inhibitor-nalidixic acid-on DNA supercoiling by wild-type and mutant enzymes was investigated.