Induction of Endogenous Virus and of Thymidine Kinase by Bromodeoxyuridine in Cell Cultures Transformed by Friend Virus

Abstract

Thymidine kinase positive (TK+) N type cell lines that had been transformed by spleen focus-forming virus were established by transformation with NB tropic Friend virus complex. Thymidine kinase deficient (TK-) cell clones were isolated. Some of these cell clones release 1000-to 100,000-fold reduced amounts of Friend virus complex as compared to the TK+ parental cell clone. TK-clones were grown in medium without BrdUrd. Some of these TK-clones can be induced to release endogenous helper virus and transforming spleen focus-forming virus on reexposure to 10-10-4 M BrdUrd. BrdUrd inhibits the replication of C-type tumor viruses (1), whereas in some instances BrdUrd or IdUrd can induce endogenous C-type virus (2-4). In order to study the action of BrdUrd on virus replication and its role in the induction of endogenous virus we have used Friend virus (FV) infected and transformed DBA-2 mouse spleen cells in culture. The FV complex consists of two components, the lymphatic leukemia helper virus (LLV-F) and the replication-defective erythroid cell-transforming spleen focus-forming virus (SFFV-F) (5, 6). The RNA of the two virus types is presumably different in size and structure (7). We have established various cell lines transformed by the SFFV-F (8, 9) which, after another thymidine analogue, can be phosphorylated to azidothymidine triphosphate. However, the presence of an No group at the 3' terminal of the deoxysugar interferes with esterification, so presumably azidothymidine can only be added terminally to the growing DNA strand. Both azidothymidine as well as BrdUrd can be used to decrease the virus titer of BrdUrd-sensitive erythroleukemic cells. We have isolated several BrdUrd-resistant clones by treatment of sensitive cells with high doses of BrdUrd (11) and have shown that some of these clones have either decreased or barely detectable thymidine kinase (ATP: thymidine 5'-phosphotransferase, EC 2.7.1.75) activity (11). Furthermore, they have a 108-to 104-fold decreased virus titer. The decrease in C-type virus release can also be shown by electron microscopy.A temporary thymidine kinase activation is observed if BrdUrd is added to some virus negative lines. The same cells release large numbers of endogenous C-type and spleen focusforming virus on exposure to BrdUrd but not to azidothymidine. The RNA tumor virus which is induced by BrdUrd has mainly N-type host range properties unlike the original NB type FV complex which has been used for the transformation of our erythroid cell lines. Thymidine kinase induction and virus induction are always correlated. We have independent evidence (Ostertag, Crozier, and Swetly, unpublished)

CDK9 inhibitor FIT-039 prevents replication of multiple DNA viruses

“…The number of available antiviral drugs has increased continually since the development of azidothymidine and acyclovir (ACV) in the 1970s (1,2). However, this has resulted in the emergence of drugresistant viruses, including HIV, hepatitis B, and the herpes simplex virus (HSV), which cause drug failures (3,4).…”

Determination of the Antiretroviral Drug Zidovudine in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode

“…During prolonged AZT treatment, HIV has the ability to increase its resistance to AZT by mutating its reverse transcriptase. In order to slow down the process of developing resistance, physiccians generally recommend that AZT be given in combination with another reverse transcriptase inhibitor and an antiretroviral from another group, such as a protease inhibitor or a non-nucleoside reverse transcriptase inhibitor [1][2][3][4][5][6][7][8].…”

The Friend Virus Genome: Partial Characterization of a Complete DNA Copy

“…The assay conditions have been described previously (Ostertag et al 1974). Spleen focus formation was measured IO days after injection of cellular supernatant into DBA/2J or BALB/c mice.…”