[The effect of sodium butyrate and luminol on reciprocal exchanges and gene conversion during extrachromosomal DNA recombination in cultured animal cells].

For determination of the extrachromosomal homologous DNA recombination efficiency, somatic cells of various lines have been transformed with plasmid DNAs which contain copies of neo-gene with non-overlapping deletions. Reconstruction of the neo-gene functional activity, which imparts a geneticin-resistant phenotype to cells, indicates that recombination has occurred. If dP1 and dR copies of the neo-gene are used, a single (reciprocal) exchange is necessary for reconstruction of the neo-gene by homologous DNA recombination, but a double exchange (gene conversion) is needed in the case of dP1 and dS copies. It is shown that in human cells of line HeLa and in mouse cells of line LMtk-, in contrast to the Chinese hamster cells of line A238, the frequency of double exchanges is comparable to that of the single DNA exchanges which is an evidence of participation in DNA recombination of gene conversion in addition to a single exchange mechanism. The treatment of cells with sodium butyrate and luminol exerts different influences on the rate of the single DNA exchanges and on that of gene conversion (double exchanges) in cells of lines LMtk- and HeLa, respectively. Essential distinctions in correlation of the single DNA exchange frequency and the gene conversion frequency in cells of the studied lines, and the possibility to distinguish between these mechanisms of recombination, under the treatment by sodium butyrate and luminol, may suggest the existence of two mechanisms of homologous DNA recombination in cultured animal cells, which function independently of one another, to a considerable extent.