Mechanism of activation of the vav protooncogene.
vav is a human locus that appears to be specifically expressed in cells of hematopoietic origin regardless of their differentiation lineage. This gene was first identified as a result of its malignant activation during the course of gene transfer assays (Katzav, S., Martin-Zanca, D., and Barbacid, M. EMBO J., 8: 2283-2290, 1989). In this study, we report the isolation of complementary DNA clones containing the entire coding sequence of the mouse vav protooncogene. Antisera raised against a peptide corresponding to a predicted hydrophilic domain have allowed us to identify the product of the vav gene as a 95,000 Da protein. Analysis of the deduced amino acid sequence of p95vav revealed an amino-terminal leucine-rich region not present in the activated vav oncogene. This region consists of an amphipathic helix-loop-helix followed by a leucine zipper, a structure reminiscent of the carboxy-terminal region of myc proteins and the steroid binding domain of nuclear receptors. In vitro mutagenicity studies have indicated that removal of the amphipathic helix-loop-helix is sufficient to activate the transforming potential of human and mouse vav protooncogenes. vav proteins also possess a cysteine-rich domain whose sequence predicts the formation of two putative metal binding-like domains, Cys-X2-Cys-X13-Cys-X2-Cys and His-X2-Cys-X6-Cys-X2-His. Replacement of some of these cysteine and histidine residues completely abolished the transforming activity of vav genes. Further examination of the alignment of cysteine residues in this region revealed an alternative structure, Cys-X2-Cys-X13-Cys-X2-Cys-X7-Cys-X6-Cys, which is reminiscent of the phorbol ester binding domain of protein kinase C. A similar domain has been recently identified in a second enzyme, diacylglycerol kinase. These structural similarities, along with its expression pattern, suggest that the vav protooncogene codes for a new type of signal-transducing molecule that may play an important role in controlling hematopoiesis.
Coppola
J
J
Department of Molecular Biology, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, New Jersey 08543.
Bryant
S
S
Koda
T
T
Conway
D
D
Barbacid
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010957:Plasmids; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics*; D051567:Proto-Oncogene Proteins c-vav; D011519:Proto-Oncogenes; D012689:Sequence Homology, Nucleic Acid
D018797:Cell Cycle Proteins; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; C496618:VAV1 protein, human; C496619:Vav1 protein, mouse