A STUDY OF THE PENETRATION OF MAMMALIAN CELLS BY DEOXYRIBONUCLEIC ACIDS

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Abstract
Tritium-labeled deoxyribonucleic acid (DNA) from pneumococci and from human leukocytes was added to growing cultures of HeLa cells at 37[degree]C. Autoradio-graphy revealed an extensive localization of tritium in the nuclear regions. The label could not be removed by treatment with ribo-nuclease or dilute perchloric acid, but quantitative removal from the cells could be effected with deoxyribonuclease. Chemical and radioactivity determinations on nuclei acids isolated from the exposed HeLa. cells revealed the presence of tritium in all 4 DNA bases. About 12 [mu]g. of tritiated DNA was recovered from 6 X 106 HeLa cells which had been exposed for 24 hours to 240 [mu]g. of the human DNA. From this, it is concluded that the amount of DNA, or its degradation products, taken up by the cells was equivalent to at least 10 per cent of the normal HeLa cell complement.