Cells nonproductively transformed by Abelson murine leukemia virus express a high molecular weight polyprotein containing structural and nonstructural components.

Abstract

Cell clones nonproductively transformed by the replication-defective Abelson strain of murine leukemia virus (AbLV) were analyzed for type C viral antigen expression by competition immunoassay. AbLV-transformed mink non-producer lines were found to express a 110,000- to 130,000-molecular weight polyprotein containing murine leukemia virus gag proteins p15 and p12 covalently linked to nonstructural AbLV-coded component(s) of around 80,000-100,000 molecular weight. This polyprotein lacked detectable antigenic cross-reactivity with other virion-coded gag gene proteins such as p30, p10, the viral reverse transcriptase (RNA-dependent DNA polymerase), or the major viral envelope glycoprotein, gp70. By analogy to earlier data on feline and avian sarcoma viruses, these results suggest that a portion of this polyprotein might represent the AbLV src gene product and that in translation it is initially linked in precursor form to gag structural proteins. Superinfection of mink cells nonproductively transformed by AbLV--with either a wild mouse amphotropic type C virus isolate, 4070-A, or with the endogenous cat virus, RD114--led to production of pseudotype virus containing high concentrations of the AbLV-coded precursor polyprotein.

Abelson virus potentiates long-term growth of mature B lymphocytes.

“…However, immunofluorescent staining of these cells showed that they lacked mlg. In contrast, considering all three experiments ( (44,68). To determine the relationship of the LPS-selected cell lines to other A-MuLV-derived cell lines, we examined the expression of P160v-abl in a representative series of isolates by SDS-PAGE analysis of [35S]methioninelabeled cell lysates.…”

“…In most cases, cells were analyzed for the presence of mIg with an affinity-purified polyvalent rabbit anti-mouse Ig reagent (Cappel Laboratories, West Chester, Pa.). To detect mIgM, an affinitypurified rabbit anti-mouse IgM (H-and L-chain-specific) reagent which were previously coated with affinity-purified polyvalent rabbit anti-mouse Ig (5 ,ig/ml) and blocked with 1% bovine serum albumin in PBS (pH 7.4) to prevent nonspecific protein binding (28,44 (6,31).…”

Four different classes of retroviruses induce phosphorylation of tyrosines present in similar cellular proteins.

“…Thus, it is presumed that transformation by these defective viruses is due to the cell-related sequences. In each case, these are probably expressed as a single polypeptide, containing viral structural protein determinants fused to the cellular protein determinants (17,20,22,24,30,42).…”

Activation of the c-abl oncogene by viral transduction or chromosomal translocation generates altered c-abl proteins with similar in vitro kinase properties.

“…The only detectable gene product of A-MuLV is a fusion between amino-terminal sequences of the M-MuLV gag polyprotein and c-abl-derived sequences (23,39). Wild-type murine v-abl (v-abl P160) is a 160,000-molecular-weight protein (25) that is phosphorylated on tyrosine in vivo (27) and is a tyrosine-specific kinase in vitro (34) (see Fig.…”