Temperature-sensitive transformation by an Abelson virus mutant encoding an altered SH2 domain.
Abelson murine leukemia virus (Ab-MLV) encodes the v-Abl protein tyrosine kinase and induces transformation of immortalized fibroblast lines and pre-B cells. Temperature-sensitive mutations affecting the kinase domain of the protein have demonstrated that the kinase activity is absolutely required for transformation. Despite this requirement, mutations affecting other regions of v-Abl modulate transformation activity. The SH2 domain and the highly conserved FLVRES motif within it form a phosphotyrosine-binding pocket that is required for interactions between the kinase and cellular substrates. To understand the impact of SH2 alterations on Ab-MLV-mediated transformation, we studied the Ab-MLV mutant P120/R273K. This mutant encodes a v-Abl protein in which the beta B5 arginine at the base of the phosphotyrosine-binding pocket has been replaced by a lysine. Unexpectedly, infection of NIH 3T3 or pre-B cells with P120/R273K revealed a temperature-dependent transformation phenotype. At 34 degrees C, P120/R273K transformed about 10-fold fewer cells than wild-type virus of equivalent titer; at 39.5 degrees C, 300-fold fewer NIH 3T3 cells were transformed and pre-B cells were refractory to transformation. Temperature-dependent transformation was accompanied by decreased phosphorylation of Shc, a protein that interacts with the v-Abl SH2 and links the protein to Ras, and decreased induction of c-Myc expression. These data suggest that alteration of the FLVRES pocket affects the ability of v-Abl to interact with at least some of its substrates in a temperature-dependent fashion and identify a novel type of temperature-sensitive Abelson virus.
Mainville
C A
CA
Department of Pathology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Parmar
K
K
Unnikrishnan
I
I
Gong
L
L
Raffel
G D
GD
Rosenberg
N
N
D016475:3T3 Cells; D000011:Abelson murine leukemia virus / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology; D000818:Animals; D001402:B-Lymphocytes / Q000821:virology; D002461:Cell Line, Transformed; D002472:Cell Transformation, Viral; D005814:Genes, Viral; D051379:Mice; D009154:Mutation; D016374:Oncogene Proteins v-abl / Q000737:chemistry / Q000235:genetics; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma; D017697:Premenopause; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013696:Temperature; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism; D018909:src Homology Domains / Q000235:genetics*
D016374:Oncogene Proteins v-abl; D016271:Proto-Oncogene Proteins c-myc; D018631:ras Proteins