During a single cycle of multiplication of type 4 adenovirus in HeLa cells an average 2-fold increase in total DNA occurred over that measured in uninfected cells. Of the total DNA from infected cells about 23 per cent was extractable into 0.15 M NaCl, a quantity approximately four and a half times greater than that of the DNA obtained from normal cells in 0.15 M NaCl. Ninety to 99 per cent of infectious virus was also extracted into the 0.15 M NaCl fraction. Concurrently with the accumulation of DNA in virus-infected cells there occurred a 2-fold increase in total protein. The proportionate increases in protein were approximately equal in 0.15 M NaCl and water extracts of infected cells. High speed centrifugation indicated that the bulk of the DNA and protein was not directly associated with infectious viral particles. Although in virus-infected cells a markedly increased synthesis occurred of a DNA which had solubility properties different from the major portion of normal host DNA, nucleotide analysis did not reveal any other qualitative differences. However, a marked change in nucleotide molar ratios was observed in the 0.15 M NaCl-soluble DNA from virus-infected cells.
It seems apparent from the findings that the biochemical alterations found in HeLa cells infected with type 4 adenovirus are intimately related to the infectious process.