v-Myb DNA binding is required to block thrombocytic differentiation of Myb-Ets-transformed multipotent haematopoietic progenitors.
The E26 avian leukaemia virus encodes a fusion oncoprotein consisting of truncated versions of the c-Myb and c-Ets-1 transcription factors. When used to infect embryonic chicken haematopoietic cells two types of self-renewing progenitors are obtained, namely myeloblasts and 'MEPs' (Myb-Ets progenitors). In earlier work we have shown that myeloblasts transformed by the ts21 mutant of E26, which has a lesion in v-Myb, can be induced to differentiate into macrophages following shift to the non-permissive temperature. Here we show that the ts21 v-Myb is temperature sensitive for DNA binding in band shift experiments and that its inactivation in transformed MEPs induces their maturation into thrombocytes. The MEP transforming capacity of v-Myb is not confined to its fusion with v-Ets, as it is also seen with a virus that co-expresses tsMyb with v-ErbB. As with wild-type E26-transformed MEPs, ts21-transformed MEPs are multipotent, differentiating into eosinophils and myeloblasts following treatment with 12-O-tetradecanoylphorbol-13-acetate. In addition, ts21-transformed myeloblasts differentiate into macrophages when shifted to the non-permissive temperature. This shows that v-Myb blocks haematopoietic differentiation at two distinct stages. In contrast, v-Ets inactivation in MEPs transformed by a ts E26 mutant with a lesion in the corresponding oncoprotein leads to their differentiation into erythrocytes, myeloblasts and probably eosinophils. These data show that the two domains of Myb-Ets selectively affect decision making processes in different types and stages of haematopoietic cells.
Frampton
J
J
Differentiation Programme, European Molecular Biology Laboratory, Heidelberg, Germany.
McNagny
K
K
Sieweke
M
M
Philip
A
A
Smith
G
G
Graf
T
T
D000123:Acetyltransferases; D000818:Animals; D001792:Blood Platelets / Q000166:cytology* / Q000378:metabolism; D002454:Cell Differentiation; D002478:Cells, Cultured; D002642:Chick Embryo; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015672:Erythroid Precursor Cells / Q000166:cytology; D006410:Hematopoiesis / Q000502:physiology*; D009154:Mutation / Q000502:physiology; D020626:Oncogene Proteins v-myb; D011401:Promoter Regions, Genetic / Q000235:genetics; D011506:Proteins / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology; D050783:Proto-Oncogene Proteins c-ets; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000096:biosynthesis; D015682:Retroviridae Proteins, Oncogenic / Q000235:genetics / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism; D013696:Temperature; D014157:Transcription Factors; D016212:Transforming Growth Factor beta / Q000096:biosynthesis
D004268:DNA-Binding Proteins; D020626:Oncogene Proteins v-myb; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D015682:Retroviridae Proteins, Oncogenic; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D012701:Serotonin; D004247:DNA; D000123:Acetyltransferases; C077509:mim-1 protein, Gallus gallus; D016392:Proto-Oncogene Proteins pp60(c-src)