Abelson murine leukemia virus-infected cell lines defective in transformation

Abstract

The isolation of two distinct classes of transformation-defective cell lines nonproductively infected with Abelson leukemia virus (AbLV) is described. One group was selected as spontaneous revertants of an AbLV-transformed mink cell line. Mutants of this group are shown to be defective both in transformation and in expression of gag gene proteins (p15 and p12) encoded by the amino terminal region of the AbLV genome. Superinfection of such cell clones by various helper viruses led to rescue of wild-type AbLV, arguing that the transformation defect in the morphologically reverted clones involves a defect in cellular genes influencing transformation rather than in the viral genome itself. Mutants of the second group were isolated by screening single cell clones, newly infected by AbLV pseudotype virus, for expression of p12 antigen in the absence of either transformation or virion production. Twenty such mutants were selected. All clones except one expressed high levels of p15 and p12 in the absence of detectable levels of other gag gene-coded structural proteins. One clone was also positive for envelope glycoprotein (gp70) apparently encoded by a replication-defective helper virus mutant. In the second group of mutant cell clones, attempts to isolate wild-type AbLV were unsuccessful. Moreover, transformation could be induced following superinfection with wild-type AbLV pseudotype virus but not with superinfection by helper virus alone. The possibility that these latter mutants may be viral rather than cellular in origin is discussed.