Nucleic Acids Research Advance Access published online on October 24, 2007
Nucleic Acids Research, doi:10.1093/nar/gkm675
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Molecular Biology |
Oncogenic point mutations in the Myb DNA-binding domain alter the DNA-binding properties of Myb at a physiological target gene
Institut für Biochemie, Westfälische-Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 2, D-48149 Münster, Germany
*To whom correspondence should be addressed. Tel: +49 251 833 3203; Fax: +49 251 833 3206; Email: klempna{at}uni-muenster.de
Received May 8, 2007. Revised July 13, 2007. Accepted August 19, 2007.
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.
Present address: Daniel Braas, University of California, Los Angeles, California 90095-1662, USA
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors