Oncogenic point mutations in the Myb DNA-binding domain alter the DNA-binding properties of Myb at a physiological target gene.
The oncoprotein v-Myb of avian myeloblastosis virus (AMV) transforms myelomonocytic cells by deregulating specific target genes. Previous work has shown that the oncogenic potential of v-Myb was activated by truncation of N- and C-terminal sequences of c-Myb and was further increased by amino acid substitutions in the DNA-binding domain and other parts of the protein. We have analyzed the activation of the chicken lysozyme gene which is strongly activated by c-Myb but not by its oncogenic counterpart v-Myb. We report that Myb acts on two different cis-regulatory elements, the promoter and an enhancer located upstream of the gene. Interestingly, the activation of the enhancer was abolished by the oncogenic amino acid substitutions. We demonstrated that a single Myb-binding site is responsible for the activation of the lysozyme enhancer by Myb and showed that the v-Myb protein of AMV was unable to bind to this site. Our data demonstrate for the first time that oncogenic activation of Myb alters its DNA-binding specificity at a physiological Myb target gene.
Ivanova
Olga
O
Institut für Biochemie, Westfälische-Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 2, D-48149 Münster, Germany.
Braas
Daniel
D
Klempnauer
Karl-Heinz
KH
D019943:Amino Acid Substitution; D000818:Animals; D009189:Avian Myeloblastosis Virus / Q000235:genetics; D001665:Binding Sites; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism; D002461:Cell Line, Transformed; D002645:Chickens / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D020570:Genes, myb; D009113:Muramidase / Q000235:genetics; D020626:Oncogene Proteins v-myb / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism; D015533:Transcriptional Activation; D000099232:Proto-Oncogene Protein Spi-1
D022763:CCAAT-Enhancer-Binding Protein-alpha; D004268:DNA-Binding Proteins; D009113:Muramidase; D020626:Oncogene Proteins v-myb; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D000099232:Proto-Oncogene Protein Spi-1