Bone marrow-transforming activity of linker insertion mutants of Abelson murine leukemia virus.

Two sets of mutants of the Abelson murine leukemia virus, generated by linker insertion mutagenesis of a cloned proviral DNA, were tested for their ability to transform bone marrow cultures in vitro. All the viruses retained an intact tyrosine kinase domain and were competent for transformation of NIH3T3 fibroblasts in culture. One series contained 12-bp linker insertions in the regions flanking the kinase domain, and the other contained frameshift mutations that truncated the gene product downstream of the kinase domain.

Isolation and characterization of flat revertant cell lines from A-MuLV-transformed fibroblasts.

Transformation of lymphoid and fibroblastic cells by Abelson murine leukemia virus (A-MuLV) is mediated by the viral tyrosine protein kinase. We do not yet know the important target proteins in the cell, the host proteins that modulate the kinase activity, or the host proteins involved in the signal-transduction pathway ultimately leading to altered patterns of cell growth. As a first step toward identifying these host proteins, we have isolated and characterized several flat revertant cell lines from transformed lines carrying v-abl.

Abelson murine leukemia virus induces platelet-derived growth factor-independent fibroblast growth: correlation with kinase activity and dissociation from full morphologic transformation.

Abelson murine leukemia virus (A-MuLV) encodes a single protein product, a tyrosine-specific protein kinase, whose activity is necessary for cell transformation by this retrovirus. Using a defined medium culture system, we demonstrate that transformation of NIH 3T3 fibroblasts by A-MuLV abrogates their normal requirement for platelet-derived growth factor (PDGF) for cell growth. Analysis of constructed insertional mutant viruses revealed an absolute correlation between A-MuLV-encoded tyrosine kinase activity and PDGF-independent fibroblast growth.

Insertional mutagenesis of the Abelson murine leukemia virus genome: identification of mutants with altered kinase activity and defective transformation ability.

A library of Abelson murine leukemia virus (A-MuLV) proviral DNAs with 12- or 6-base-pair (bp) insertional mutations was constructed. The 29 mutations characterized spanned the entire protein-coding region of the provirus. We tested the effects of these mutations both on the kinase activity of the gag-abl fusion protein encoded by the provirus and on the ability of the provirus to transform NIH 3T3 fibroblasts.

Insulin stimulates phosphorylation of a 120-kDa glycoprotein substrate (pp120) for the receptor-associated protein kinase in intact H-35 hepatoma cells.

The insulin receptor possesses protein kinase activity, which may play a role in mediating insulin action. Recently, we have identified a glycoprotein (pp120) in rat liver plasma membranes that is phosphorylated by the solubilized insulin receptor in a cell-free system. We now report that insulin stimulates phosphorylation of pp120 in intact H-35 cells.