Effect of cell cycle position on transformation by microinjection

We have investigated the effect of cell cycle position on the efficiency of transformation by microinjection. Linear recombinant plasmids transform synchronized cells with similar frequencies following injections at all cell cycle stages, whereas supercoiled molecules show a decreased ability to generate transformants in early S phase. This inhibition is not due to an inability to transiently express a transferred gene, since cells at all stages of the cycle efficiently expressed a hamster adenine phosphoribosyltransferase gene introduced on a supercoiled plasmid. Southern transfer analyses of the cell cycle specific transformants revealed that tandem arrays of plasmids, integrated into the host chromosomes, could be generated at all cell cycle stages.