No abstract

We have presented a new approach to studying bacteriophage T4 head maturation. Using a modified M-band technique, we have shown that progeny deoxyribonucleic acid (DNA) was synthesized on the host cell membrane throughout infection. This DNA was released from the membrane later in infection as the result of formation of the phage head; detachment of the DNA required the action of gene products 20, 21, 22, 23, 24, 31, 16, 17 and 49, known to be necessary for normal head formation. Gene products 2, 4, 50, 64, 65, 13 and 14, also involved in head morphogenesis were not required to detach progeny DNA from the membrane; the presence of the phage tail and tail fibers also was not required. DNA was released in the form of immature heads and initially was sensitive to deoxyribonuclease (DNase). Conversion to DNase resistance followed rapidly. The amount of phage precursors present at the time of DNA synthesis determined the time of onset and detachment rate of DNA from the M band as well as the kinetics by which the detached DNA become DNase resistant. E. coli B was used as the restrictive host. Both were obtained from E. B. Goldberg. Bacteriophage strains. For bacteriophage strains used, see Table 1. Media. Phage (P) broth (29) was used as the growth medium. Dilution fluid and washing fluid used in phage purification have been described (4). Chemicals and radiochemicals. Sarkosyl NL-30 was a gift of Geigy Chemical Corporation, 359

Replicating Epstein-Barr virus (EBV) DNA molecules isolated from superinfected Raji cells were shown to consist of 80S to 65S and 58S (mature) molecules. Pulse-chase experiments showed that radioactive label of DNA molecules with the larger sedimentation coefficients was partially chased into 58S labeled forms. Formation of large concatemers of viral DNA could not be detected at any time after superinfection. The continuous presence of the 65S viral DNA intermediate throughout the replicative cycle combined with the observed inhibition of EBV DNA synthesis by addition of nontoxic levels of ethidium bromide to the superinfected cell culture led us to propose that EBV replication proceeds via a relaxed circular DNA intermediate.

Low concentrations of adenine arabinoside inhibited growth of two Epstein-Barr virus producer cell lines in culture, while not significantly affecting a nonproducer cell line and a B-cell-negative line. These observations were extended to include freshly infected cells. Mitogen-stimulated human umbilical cord blood lymphocytes were unaffected by the drug at concentration levels that inhibited [3H]thymidine incorporation into the DNA of Epstein-Barr virus-stimulated cells. DNA synthesis in Epstein-Barr virus-superinfected Raji cells was also adversely affected by adenine arabinoside. However, these same low concentrations of adenine arabinoside in the triphosphate form produced less effect on DNA synthesis in nuclear systems and DNA polymerase assays than on growth or DNA synthesis in whole cells. Therefore the effects reported here of low concentrations of the drug on whole cells may be only in part related to DNA polymerase inhibition. The work reported here suggests that adenine arabinoside has multiple sites of action in infected cells. The synthesis of 9-fp-D-arabinofuranosyladenine (adenine arabinoside, or ara-A) as a potential anticancer agent was first reported in 1960 (18). Since then ara-A has been reported to have antitumor and antiviral effects for tissue culture cells and laboratory animals and in clinical use in treatment of certain virally caused diseases. Reports between 1964 and 1968 have shown that ara-A has specific antiviral effects in tissue culture for herpes, pox, and Rous sarcoma viruses (11, 29, 32; R. W. Sidwell, G. Arnett, and G. J. Dixon, Program Abstr. Intersci. Conf. Antimicrob. Agents Chemother., 7th, Chicago, Ill., Abstr. no. 64, 1967). Furthermore, inhibition of mammalian ribonucleotide reductase and DNA polymerase by ara-A were demonstrated (12, 22). Certain studies have shown that mammalian a polymerases are sensitive to ara-A (23-25;

No abstract