Differential sensitivity of v-Myb and c-Myb to Wnt-1-induced protein degradation.
Recently we have shown that the c-myb proto-oncogene product (c-Myb) is degraded in response to Wnt-1 signaling via the pathway involving TAK1 (transforming growth factor-beta-activated kinase), HIPK2 (homeodomain-interacting protein kinase 2), and NLK (Nemo-like kinase). NLK and HIPK2 bind directly to c-Myb, which results in the phosphorylation of c-Myb at multiple sites, followed by its ubiquitination and proteasome-dependent degradation. The v-myb gene carried by avian myeloblastosis virus has a transforming capacity, but the c-myb proto-oncogene does not. Here, we report that two characteristics of v-Myb make it relatively resistant to Wnt-1-induced protein degradation. First, HIPK2 binds with a lower affinity to the DNA-binding domain of v-Myb than to that of c-Myb. The mutations of three hydrophobic amino acids on the surface of the DNA-binding domain in v-Myb decrease the affinity to HIPK2. Second, a loss of multiple NLK phosphorylation sites by truncation of the C-terminal region of c-Myb increases its stability. Among 15 putative NLK phosphorylation sites in mouse c-Myb, the phosphorylation sites in the C-terminal region are more critical than other sites for Wnt-1-induced protein degradation. The relative resistance of v-Myb to Wnt-1-induced degradation may explain, at least in part, the differential transforming capacity of v-Myb versus c-Myb.
Laboratory of Molecular Genetics, RIKEN Tsukuba Institute, 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074, Japan.
Chie
C
Kanei-Ishii
Teruaki
T
Nomura
Jun
J
Tanikawa
Emi
E
Ichikawa-Iwata
Shunsuke
S
Ishii
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007930:Leucine / Q000737:chemistry; D051379:Mice; D008954:Models, Biological; D009154:Mutation; D020626:Oncogene Proteins v-myb / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D020598:Proto-Oncogene Proteins c-myb / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection; D020798:Two-Hybrid System Techniques; D051153:Wnt Proteins; D051155:Wnt1 Protein
D002352:Carrier Proteins; C000715470:MAS1 protein, human; D020626:Oncogene Proteins v-myb; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D020598:Proto-Oncogene Proteins c-myb; C495247:WNT1 protein, human; D051153:Wnt Proteins; D051155:Wnt1 Protein; C495246:Wnt1 protein, mouse; D004247:DNA; D015500:Chloramphenicol O-Acetyltransferase; D005982:Glutathione Transferase; C115114:HIPK2 protein, human; C492003:Hipk2 protein, mouse; D017346:Protein Serine-Threonine Kinases; D007930:Leucine