title: Oncogenic mutations cause dramatic, qualitative changes in the transcriptional activity of c-Myb.
abstract: The v-Myb oncoprotein encoded by Avian Myeloblastosis Virus is highly oncogenic, induces leukemias in chickens and mice and transforms immature hematopoietic cells in vitro. The v-Myb protein is a mutated and truncated version of c-Myb, a DNA-binding transcription factor expressed in many cell types that is essential for normal hematopoiesis. Previous studies suggested that two types of differences, DNA binding domain mutations and the deletion of a C-terminal negative regulatory domain were important for increasing the transforming activity of v-Myb. Here, we combined structure-function studies of the v-Myb and c-Myb proteins with unbiased microarray-based transcription assays to compare the transcriptional specificities of the two proteins. In human cells, the v-Myb and c-Myb proteins displayed strikingly different activities and regulated overlapping, but largely distinct sets of target genes. Each type of mutation that distinguished v-Myb from c-Myb, including the N- and C-terminal deletions, DNA binding domain changes and mutations in the transcriptional activation domain, affected different sets of target genes and contributed to the different activities of c-Myb and v-Myb. The results suggest that v-Myb is not just a de-repressed version of c-Myb. Instead, it is a distinct transcriptional regulator with a unique set of activities.
authors.affiliation: Department of Molecular Genetics and Microbiology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131-0001, USA.
authors.forename: F
authors.initials: F
authors.lastname: Liu
authors.forename: W
authors.initials: W
authors.lastname: Lei
authors.forename: J P
authors.initials: JP
authors.lastname: O'Rourke
authors.forename: S A
authors.initials: SA
authors.lastname: Ness
mesh_terms: D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D017931:DNA Primers; D006801:Humans; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D009857:Oncogenes; D020598:Proto-Oncogene Proteins c-myb / Q000502:physiology*; D014158:Transcription, Genetic / Q000235:genetics*
chemical_list: D017931:DNA Primers; D020598:Proto-Oncogene Proteins c-myb