title: Conditional inhibition of erythroid differentiation by c-Myb/oestrogen receptor fusion proteins.
abstract: The c-myb proto-oncogene encodes a transcription factor that has been implicated in the regulation of haemopoietic cell differentiation and appears also to be required for cell proliferation in a number of different lineages. Typically, transcription of c-myb is down-regulated during haemopoietic cell differentiation, and it has been found in several erythroid and myeloid cell lines that constitutive c-myb expression, from a transfected plasmid, blocks this differentiation process. To investigate further the activity of c-myb in haemopoietic cell differentiation, we have transfected Friend murine erythroleukaemia (F-MEL) cells with plasmids encoding conditionally active c-Myb/oestrogen receptor (Myb/ER) fusion proteins. Transcriptional activity of the Myb/ER fusion proteins was found to be strictly hormone-dependent, and this property was correlated with the ability of these proteins to inhibit erythroid differentiation. From analysis of a Myb/ER protein that lacks the c-Myb transactivation domain, it was apparent that the C-terminal ER transactivation domain could substitute for that of c-Myb in inhibition of differentiation. Activation of Myb/ER in F-MEL cells had no effect upon the early and transient inhibition of entry into S phase associated with dimethyl sulfoxide (DMSO) induction. Further analyses of alpha-globin and PU.1 gene transcription suggested that c-Myb is unable to influence gene expression immediately following DMSO-induction and that inhibition of F-MEL cell differentiation must therefore result from the function of c-Myb in the post-commitment period. Nonetheless, c-Myb had effects on the erythroid differentiation programme that were clearly dissociated from its role in cell proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Ludwig Institute for Cancer Research, St. Mary's Hospital Medical School, London, UK.
authors.forename: J J
authors.initials: JJ
authors.lastname: Lyon
authors.forename: R J
authors.initials: RJ
authors.lastname: Watson
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002454:Cell Differentiation; D002455:Cell Division; D004268:DNA-Binding Proteins / Q000235:genetics; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D050981:Erythroid-Specific DNA-Binding Factors; D004915:Leukemia, Erythroblastic, Acute / Q000473:pathology*; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D020598:Proto-Oncogene Proteins c-myb; D011960:Receptors, Estrogen / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics; D015533:Transcriptional Activation
chemical_list: D004268:DNA-Binding Proteins; D050981:Erythroid-Specific DNA-Binding Factors; D011518:Proto-Oncogene Proteins; D020598:Proto-Oncogene Proteins c-myb; D011960:Receptors, Estrogen; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D004121:Dimethyl Sulfoxide