Microinjected pBR322 stimulates cellular DNA synthesis in Swiss 3T3 cells

J. K. Hyland, R. R. Hirschhorn, C. Avignolo, W. E. Mercer, M. Ohta, N. Galanti, G. J. Jonak, R. Baserga

Research output: Contribution to journalArticlepeer-review


When pBR322 is manually microinjected into the nuclei of quiescent Swiss 3T3 cells it stimulates the incorporation of [3H]thymidine into DNA. The evidence clearly shows that this increased incorporation that is detected by in situ autoradiography in microinjected cells represents cellular DNA synthesis and not DNA repair or plasmid replication. The effect is due to pBR322 and not due to impurities, mechanical perturbances due to the microinjection techniques, or aspecific effects. This stimulation is striking in Swiss 3T3 cells. Some NIH 3T3 cells show a slight stimulation, but hamster cells, derived from baby hamster kidney (BHK) cells, are not stimulated when microinjected with pBR322. The preliminary evidence seems to indicate that the integrity of the pBR322 genome is important for the stimulation of cellular DNA synthesis in quiescent Swiss 3T3 cells. These results, although of a preliminary nature, are of interest because they indicate that a prokaryotic genome may alter the cell cycle of mammalian cells. From a practical point of view the stimulatory effect of microinjected pBR322 on cellular DNA synthesis has a more immediate interest, because pBR322 is the vector most commonly used for molecular cloning and 3T3 cells are very frequently used for gene transfer experiments.

Original languageEnglish (US)
Pages (from-to)400-404
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number2 I
StatePublished - 1984
Externally publishedYes

ASJC Scopus subject areas

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