Nucleic Acid Metabolism of Virus‐infected Hela Cells*

Abstract

The study of the chemistry of virus-infected cells cannot yet claim a molecular interpretation for the genesis of the viral cytopathic effect. However, many striking observations have been made that must be accounted for in any molecular theory of viral cytopathology. From the viewpoint of comparative virology, the most consistent viral-induced aberrations involve the nucleic acids. The findings that we describe here concern the several classes of these important compounds, their relations to the cell architecture, and their dynamics relative to a single cycle of infection. These experiments with HeLa cells and poliovirus are part of a continuing investigation and are contributions made in collaboration with our colleagues. Some results have been published; others have not been made available previously.Part of the record in the literature (Payne et al., 1958) describes how a single cycle of infection of monolayers of HeLa cells may be effected with high concentrations of poliovirus. It suffices here to say that interpretations at the cellular level of the present observations made on multicellular cultures have been justified.The first experiments concern the stability of the cell structure after infection, particularly in regard to those elements that will be considered in the metabolic studies. Transudation PhenomenonHeLa cells are readily labeled with P3* by allowing them to grow in a medium containing radioactive inorganic phosphate. The P32 is incorporated into a number of large molecules and structures such as the nucleic acids, microsomes, and mitochondria. When such labeled cells are transferred to unlabeled maintenance medium (Scherer, 1953) and incubated, some of the radioactive phosphorus leaks from the cell. Initially, the process is rapid, but it soon subsides and, by 5 hours, an equilibrium seems to be established between this exchangeable phosphate of the cell and that of the medium. After this time the P32 of the medium ceases to rise and remains constant (FIGURE 1).When poliovirus is added to such a culture of labeled cells, the process of P 3 2 exchange closely parallels that of the control until the sixth hour of infection. At this time, the curves for the release of Pa2 diverge (FIGURE 1). Progressively, the transudation of labeled cellular elements is accelerated in the infected culture. A preliminary examination of this transudate shows it to be composed of both acid-soluble and acid-insoluble elements. The soluble fraction is a complex mixture of nucleotides, nucleosides, and inorganic phosphate.