Inhibition of erythro-myeloid differentiation by constitutive expression of a DNA binding-deficient c-myb mutant: implication for c-myb function.
The c-myb proto-oncogene encodes a nuclear protein involved in the regulation of cell proliferation, differentiation, and development. Myb protein contains a DNA binding and a transactivating domain thought to mediate its biologic properties. The DNA binding domain consists of three repeats (R1, R2, and R3), each containing a highly conserved motif of tryptophan residues. A c-myb mutant (DR1-myb) lacking the last 46 amino acids of R1 and 23 amino terminal residues of R2, a region homologous to the ADA-2 yeast transcriptional adaptor, lost DNA binding ability, but remained able to transactivate the human heat-shock promoter. Transfection of murine 32D and murine erythroleukemia (MEL) cell lines with DR1-myb caused inhibition of cellular differentiation induced by granulocyte colony-stimulating factor (G-CSF) and dimethyl sulfoxide (DMSO), respectively. A second c-myb mutant (D-ADA2-myb) lacking the first 23 amino acids of R2, also lost DNA binding and transactivation activity, but did not inhibit DMSO-induced differentiation of MEL transfected cells. These findings suggest that deletion of R1 activates a DNA binding-independent mechanism of c-myb function, which may involve interaction of Myb with cellular factors.
Sala
A
A
Department of Microbiology and Immunology, Jefferson Cancer Institute, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Bellon
T
T
Melotti
P
P
Peschle
C
C
Calabretta
B
B
D000818:Animals; D001665:Binding Sites; D002454:Cell Differentiation / Q000187:drug effects; D006224:Cricetinae; D004247:DNA / Q000378:metabolism*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004920:Erythropoiesis / Q000502:physiology; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D006410:Hematopoiesis / Q000502:physiology*; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute / Q000473:pathology; D051379:Mice; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D020598:Proto-Oncogene Proteins c-myb; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D020598:Proto-Oncogene Proteins c-myb; D011993:Recombinant Fusion Proteins; D016179:Granulocyte Colony-Stimulating Factor; D004247:DNA; D004121:Dimethyl Sulfoxide