Direct transfer of the bacterial asparagine synthetase gene to mammalian cells

Using specific mutants as a means of identification, the bacterial protein for asparagine synthetase (Asn Syn) was shown to be antigenically and electrophoretically similar to its mammalian counterpart. This observation prompted us to attempt direct transfer of the cloned bacterial gene for the enzyme to mammalian cells. DNA from the replicative form of clone M13 OriC, containing the bacterial gene for Asn Syn, was shown to be capable of causing transformation of Jensen rat Asn Syn- cells to cells capable of growth in Asn-free medium; no prior modification of the bacterial gene was required. This relatively inefficient transformation (20 colonies/micrograms DNA/10(6) cells) was sensitive or insensitive to restriction enzyme digestion of the M13 OriC DNA in complete agreement with the known restriction map of the bacterial gene. Clones of transformed rat cells contained the bacterial DNA, which was amplified if increased levels of the enzyme were demanded and lost if selection was removed. The clones also contained polysomal bacterial RNA and a new protein with properties similar but not identical to those of the bacterial enzyme. The biological significance of this unusual degree of compatibility between the prokaryotic and eukaryotic Asn Syn gene systems is discussed.