Inducibility of spleen focus-forming virus by BrdUrd is controlled by the differentiated state of the cell

Abstract All Friend cells--except thymidine kinase (ATP:thymidine 5'-phosphotransferase, EC 2.7.1.21)-deficient mutants--are highly inducible for the release of biologically active spleen focus-forming virus (SFFV) after exposure to BrdUrd. We studied SFFV production in somatic cell hybrids made between Friend leukemia cells (FLC) and cells expressing various differentiation programs. High inducibility of SFFV and release of constitutive Friend virus (FV) and SFFV are eliminated in all hybrids in which the potential for erythroid differentiation is suppressed. FV release and its induction by BrdUrd are unchanged in hybrids that maintain the expression of erythroid differentiation.