[Directed modification of the early region of T7 bacteriophage DNA by alkylation in the R-loop formed by a modified transcript].

For addressed modification of T7 phage DNA a polyalkylating derivative of T7 phage early transcript was used. The derivative was obtained by attaching polyfunctional alkylating agent N,N,N,'-tri(beta-chloroethyl)-N'-(p-formylphenyl) propylene diamine-1,3 to the transcript, their molecules being covalently bound by alkylating 4--5% of the RNA adenine and guanine residues. The polyalkylating RNA was used to form R-loops in the complementary site of T7 DNA to alkylate selectively the T7 phage early DNA. Alkylation of DNA by the modified transcript in the region of the R-loop led to the covalent binding of the transcript to the complementary site of DNA. The correct localization of this R-loop was confirmed by electron microscopy. The application of the results for the addressed mutagenesis and inactivation of selected genes is discussed.