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Abelson murine leukemia virus: characterization of a polyprotein containing phosphorylated component(s) encoded by
Abstract:
A previously described 120,000 dalton polyprotein, P120, encoded by the Abelson strain of murine leukemia virus (AbLV) is compared to translational products representing the entire Moloney murine leukemia virus (MuLV) genome. Each of three [35S]-methionine tryptic present in Moloney-MuLV Pr65gag are also represented in Pr180gag-pol. Of these, one peptide corresponding to Moloney-MuLV p12, but neither of two p30 specific peptides are present in AbLV P120. None of the twelve remaining methionine containing peptides present in AbLV P120 appear to correspond to those of either Moloney-MuLV Pr82env. AbLV P120 and a 110,000 dalton polyprotein encoded by a second transforming isolate of mouse origin, designated AK-T8, are both shown to be highly phosphorylated. Sites of phosphorylation included known phosphorylated structural (p12) components, as well as components encoded by acquired cellular sequences. Immunoprecipitates of AbLV P120 obtained from either cells or pseudotype virions are shown to contain protein kinase activity which recognizes AbLv P120 as substrate. This activity may represent an intrinsic property of the polyprotein itself or represent a cellular enzyme associated with AbLV P120 in the form of an enzyme-substrate complex.
Insights
Abelson murine leukemia virus P120 polyprotein shares some features with Moloney murine leukemia virus but has unique peptides. Both AbLV P120 and AK-T8 polyproteins are phosphorylated and exhibit protein kinase activity.
Area of Science:
- Virology
- Molecular Biology
- Oncogenic Viruses
Background:
- Abelson murine leukemia virus (AbLV) encodes a 120,000 dalton polyprotein (P120).
- Murine leukemia viruses (MuLV) are retroviruses known to cause leukemia in mice.
- Transforming retroviruses often contain unique genetic elements contributing to their oncogenic potential.
Purpose of the Study:
- To compare the Abelson strain of murine leukemia virus (AbLV) P120 polyprotein with translational products of the Moloney murine leukemia virus (MuLV) genome.
- To investigate the phosphorylation status and associated enzymatic activities of AbLV P120 and a related transforming isolate.
Main Methods:
- Comparative peptide analysis using [35S]-methionine labeling and tryptic digestion.
- Immunoprecipitation of polyproteins from cells and virions.
- Assay of protein kinase activity in immunoprecipitates.
Main Results:
- AbLV P120 contains one peptide shared with Moloney-MuLV p12, but not p30 specific peptides.
- AbLV P120 and AK-T8 polyproteins are highly phosphorylated, including acquired cellular sequences.
- AbLV P120 immunoprecipitates exhibit protein kinase activity, potentially intrinsic or via an associated enzyme.
Conclusions:
- AbLV P120 displays a distinct protein composition compared to Moloney-MuLV.
- Phosphorylation and associated protein kinase activity are notable features of AbLV P120, suggesting a role in viral oncogenesis.