@article{mbs:/content/journal/jgv/10.1099/0022-1317-52-1-189, author = "Suk, William A. and Long, Cedric W.", title = "Increased Expression of Endogenous Xenotropic Murine Retrovirus by Treatment with the Tetrapeptides, Tuftsin and Kentsin", journal= "Journal of General Virology", year = "1981", volume = "52", number = "1", pages = "189-194", doi = "https://doi.org/10.1099/0022-1317-52-1-189", url = "https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-52-1-189", publisher = "Microbiology Society", issn = "1465-2099", type = "Journal Article", abstract = "SUMMARY Enhancement of endogenous xenotropic virus expression has been found upon treatment with tetrapeptides of a high-passage clone of Balb/c (K-Balb) mouse cells transformed with Kirsten sarcoma virus. Tuftsin (Thr-Lys-Pro-Arg) and kentsin (Thr-Pro-Arg-Lys) increased the expression of virus that was infectious for rat, but not mouse, cells in a concentration-dependent fashion. The enhancement of virus expression by the tetrapeptides was proportional to the spontaneous release of virus. The infectivity of the enhanced virus was neutralized by goat anti-RLV gp70 serum. Actinomycin D inhibited the induction of virus, suggesting that enhanced expression required de novo RNA synthesis. The effects observed using K-Balb cells offer an opportunity to study the many biological effects of these peptides in a fibroblast culture system.", }