[Interaction of double-stranded DNA in the Escherichia coli RecA protein system with modified oligonucleotides containing an alkylated terminal group].

We studied modification of double-stranded DNA with chemically active homologous oligonucleotide derivatives carrying an alkylating 4-[N-2-chloroethyl-N-methylamino)benzyl]aminogroup in DNA recombination reaction promoted by E. coli RecA protein. It was shown that this chemical group does not prevent the formation of a complex between RecA protein and oligonucleotide as well as binding of this complex to double-stranded DNA. Formation of cross-links between DNA and oligonucleotide derivatives was observed at oligonucleotide lengths of no less than 30. The supercoiled form of the plasmid was alkylated with a higher efficacy than relaxed or linear form. In spite of homology between oligonucleotide and a certain region of double-stranded DNA (pBR322), cross-links were observed throughout the DNA length including nonhomologous regions. The causes of such behavior are discussed.