[Phenomenon of restriction alleviation in Escherichia coli strains]

The alleviation of foreign DNA restriction after treatment of cells by UV and gamma-rays or ocr+-gene product of T3, T7 phages has been studied. Both UV and gamma-radiation were shown to induce in restriction alleviation of unmodified phage. The results of restriction alleviation caused by T3 and T7 ocr+-gene products have been evaluated by F-lac+ transfer efficiencies in heterologic crosses and plating of unmodified phage lambda. The phenomenon of restriction alleviation was established to depend on the strain used and to be expressed mostly in AB157 and its derivatives.