Abelson murine leukemia virus mutants deficient in kinase activity and lymphoid cell transformation

Abstract

Abelson murine leukemia virus transforms both lymphoid cells and fibroblasts in vitro and induces a unique type of thymus-dependent lymphoma in vivo. Four fibroblast-transforming strains of Abelson murine leukemia virus were identified, based on the sizes of the Abelson murine leukemia virus-specific phosphoproteins produced by these isolates. Two of these strains, the standard P120and the P160-producing viruses, transformed lymphoid cells efficiently in vitro and induced Abelson disease in vivo. Two other strains, which synthesized small Abelson murine leukemia virus-specific proteins with molecular weights of 90,000 (P90) and 100,000 (P100), transformed lymphoid cells very poorly both in vitro and in vivo. The reduced oncogenic potentials of these isolates were correlated with a high level of synthesis of fairly unstable P90 and P100. In addition, neither P90 nor P100 functioned efficiently in protein kinase assays. The correlation of abnormal metabolism and deficient protein kinase activity with the reduced oncogenic potentials of these virus strains supported a direct role for these proteins and the kinase activity in transformation. Furthermore, these results suggested that the requirements for lymphoid cell transformation and fibroblast transformation are different.

Abelson virus-infected cells can exhibit restricted in vitro growth and low oncogenic potential

“…Subcutaneous tumors at the site of injection were common in the former two cases. The second is that the time course of tumor appearance in the mice injected with the P90-infected cells was similar to that found upon injection of mice with P90 virus preparations (22). We are presently examining the frequency of tumors that arise which are of host or donor origin by using F1 mice as recipients of the P90and P160-infected BALB/c lymphocytes.…”

“…Increased efficiency of target cell growth of bone marrow cells infected by the P90 strain of A-MuLV. Although the P90 strain of A-MuLV is capable of transforming NIH-3T3 fibroblasts with a high efficiency, bone marrow cells infected with P90 show a 10to 30-foldlower frequency of agar colony transformation with P120 and P160 (22). A lower efficiency of bone marrow transformation with P90 was also observed in liquid cultures, a large fraction of which failed to show detectable growth of target cells even after 17 days of culture (22).…”

“…Other mutants of A-MuLV have been isolated (P85, P90, and P100) which show no reduction in their ability to transform fibroblasts in vitro (23). However, these mutants show a 10-to 30-fold-reduced frequency of lymphoid cell transformation when the mutant and prototype virus stocks are normalized for fibroblast-transforming titers (22). Clonal cell lines transformed with either the prototype or partially defective strains express the same pre-B-cell differentiation phenotypes (intracellular IL-heavy chains of immunoglobulin M and terminal deoxynucleotidyltransferase) (3,22,25,26).…”

“…However, these mutants show a 10-to 30-fold-reduced frequency of lymphoid cell transformation when the mutant and prototype virus stocks are normalized for fibroblast-transforming titers (22). Clonal cell lines transformed with either the prototype or partially defective strains express the same pre-B-cell differentiation phenotypes (intracellular IL-heavy chains of immunoglobulin M and terminal deoxynucleotidyltransferase) (3,22,25,26). This suggests that the target cell specificity is very similar for all strains but that the efficiency of transformation, as detected by growth in liquid or soft agar cultures, varies markedly.…”

The cytostatic function of c-Abl is controlled by multiple nuclear localization signals and requires the p53 and Rb tumor suppressor gene products.

“…Normal c-Abl is unable to transform cells, even if overexpressed (Jackson and Baltimore, 1989), but can be activated to transform fibroblasts and hematopoietic cells by several distinct mechanisms, including deletions (Franz et al, 1989;Jackson and Baltimore, 1989) or point mutations (Van Etten et al, 1995) in the SH3 domain, substitution of polypeptides derived from retroviral gag (Van Etten et al, 1995), BCR (Shtivelman et al, 1985;Stam et al, 1985) or TEL (Papadopoulos et al, 1995) genes at the extreme N-terminus, and point mutations in the kinase domain (Jackson et al, 1993b). Fibroblast transformation by activated Abl requires tyrosine kinase activity (Rosenberg et al, 1980;Engelman and Rosenberg, 1987;Kipreos et al, 1987), the phosphotyrosine binding function of the SH2 domain (Mayer et al, 1992) and myristoylation (Daley et al, 1992). The functions of the c-ras (Smith et al, 1986;Stacey et al, 1991;Sawyers et al, 1995) and c-myc (Sawyers et al, 1992) genes are required for Abl transformation, and activated Abl has been identified recently as a potent stimulator of the stress-activated protein kinase pathway (Sanchez et al, 1994).…”