Myb and Ets proteins cooperate in transcriptional activation of the mim-1 promoter.
In the generation of the acutely transforming avian retrovirus E26, both myb and ets genes have been transduced, leading to the production of a Gag-Myb-Ets fusion protein. This co-occurrence of v-myb and v-ets oncogenes suggests that the two might have a functional relationship. To look for such a relationship, we tested the transcriptional activation activity of Myb alone or with coexpressed Ets-1 or Ets-2. Using the promoter of the v-Myb-inducible mim-1 gene as a target, we found that full-length c-Myb gene products were poor activators of transcription, while an oncogenic (truncated) form of this protein was a strong trans-activator. However, coexpression of Ets-2 with full-length or truncated forms of Myb greatly increased trans-activation. Coexpression of Ets-1, Fos, Jun, or Myc with Myb did not increase trans-activation of the mim-1 promoter. The ability of Myb and Ets-2 to transactivate was cooperative, since Ets-2 alone gave little or no activation. Bacterially synthesized Ets-2 protein was found to bind specifically to the mim-1 promoter, suggesting that it may be a target for both Myb and Ets proteins. Thus, Myb and Ets proteins can cooperate in transcriptional activation, and their co-occurrence in the E26 virus may reflect a functional relationship between these two oncoproteins. Truncated forms of Myb may have a reduced need for cooperating factors such as Ets-2, and this might constitute an important mechanism associated with oncogenic activation.
Dudek
H
H
Wistar Institute of Anatomy and Biology, Philadelphia, PA 19104.
Tantravahi
R V
RV
Rao
V N
VN
Reddy
E S
ES
Reddy
E P
EP
D000595:Amino Acid Sequence; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D050783:Proto-Oncogene Proteins c-ets; D020598:Proto-Oncogene Proteins c-myb; D011994:Recombinant Proteins; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D020598:Proto-Oncogene Proteins c-myb; D011994:Recombinant Proteins; D014157:Transcription Factors