Analysis of chimeric Gag-Arg/Abl molecules indicates a distinct negative regulatory role for the Arg C-terminal domain.
Arg and c-Abl represent the mammalian member of the Abelson family of nonreceptor protein tyrosine kinases. The two proteins are composed of SH2, SH3, kinase and C-terminal domains. To examine Arg structure-function relationships we analysed a Gag-Arg fusion protein, analogous to the oncogenic Gag-Abl fusion protein of Abelson Murine Leukaemia Virus and found that in contrast to Gag-Abl, it lacked transforming activity. Three observations indicated that the difference in the transforming activity was mediated by the distinct Arg and Abl C-terminal domains. (1) The analysis of chimeric Gag-Arg/Abl molecules revealed that the Arg C-terminal domain completely abrogated Gag-Abl transforming activity and that the Abl C-terminus conferred transforming activity to Gag-Arg. Substitutions of SH2 and kinase domains did not affect activity. (2) Alterations in the Arg C-terminus were observed in spontaneous foci that developed in transfections of two nontransforming chimera. (3) An engineered Gag-Arg molecule containing a truncation of almost the entire C-terminal domain, including three SH3 domain-binding sites, was oncogenic, whereas a slightly smaller truncation that deleted two of three SH3 domain-binding sites, lacked transforming activity. These observations indicate that the C-terminal domain regulates Arg biological activity in a manner distinct from c-Abl and suggest that this effect may be mediated in part by SH3 domain-binding sites.
Mysliwiec
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Department of Medical Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
Perego
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Kruh
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D016475:3T3 Cells; D000011:Abelson murine leukemia virus / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D015683:Gene Products, gag / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D008322:Mammals; D051379:Mice; D008969:Molecular Sequence Data; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D016315:Proto-Oncogene Proteins c-abl / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D014162:Transfection
D015683:Gene Products, gag; D011993:Recombinant Fusion Proteins; D011505:Protein-Tyrosine Kinases; D016315:Proto-Oncogene Proteins c-abl