HeLa cells lack recA gene

Abstract

We have been interested in the mechanism of genetic recombination. A protein coded by the recA gene of Escherichia coli has been found to facilitate the formation of recombination intermediates; roles of this protein in genetic recombination and repair have been discussed [l-3]. In view of the significant role that the recA protein seems to play in genetic recombination, we decided to examine the presence of a gene coding such a protein (recA) in eukaryotes using HeLa cells. Radioactively labelled, cloned E. coli recA DNA sequence was used as a probe to detect the presence of possible homologous nucleotide sequences in HeLa cell DNAafter restriction endonuclease digestion and Southern transfer [4]. E. coli chromosomal and hybrid plasmid (pBR322 DNA containing recA gene) were used as controls in such experiments. The basis for our experiment lies in the fact that a heterologous DNA probe can be used to detect the presence of a gene in evolutionarily divergent groups of organisms and that cloned E. coli recA gene is now available [3] which can be used as probe in such experiments. Heterologous DNA probes have been used to detect the presence of nitrogen fmtion genes in a wide variety of organisms capable of nitrogen fixation [5,6]. Also, heterologous DNA sequences have been used to detect the presence of specific genes such as histones, actin and others in a wide variety of eukaryotes [7,8].