MECHANISMS OF TRANSFORMATION OF MURINE HEMATOPOIETIC CELLS BY ME26 VIRUS

这个项目的目的是使用一种基于逆转录病毒的小鼠模型

The objective of this project is to use a retrovirus-based mouse model system to understand how inappropriate activation of transcription factors in hematopoietic cells can result in the development of leukemia. We have been studying the myb-ets-containing ME26 virus, which causes a high incidence of leukemia in mice by a novel mechanism involving the inappropriate activation of erythroid-specific genes in hematopoietic precursor cells. We have previously shown that the ME26 viral protein can transactivate the promoter of the erythroid-specific transcription factor, GATA-1, and then cooperate with the GATA-1 protein to transcriptionally activate the erythropoietin receptor and other erythroid-specific genes. This results in the unregulated proliferation of virus-infected cells in the presence of the erythroid hormone erythropoietin. In an attempt to better understand how the viral protein can transactivate the GATA-1 promoter, we engineered and analyzed deletion mutants to determine which sequences in the promoter are crucial for activation by the ME26 viral protein. Our results indicate that sequences in the 3' end of the GATA-1 promoter, which include two CACCC elements, are essential for transactivation by ME26 virus, while other upstream sites contribute to full activation by the virus. Mutation of the CACCC sites abolishes ME26 viral transactivation. The interaction of cell extracts containing ME26 viral protein and the GATA-1 fragment containing the two CACCC elements was examined by electrophoretic mobility shift analysis and the results showed no direct interaction between the two. However, we could detect the ubiquitous transcription factor Sp1 bound to this sequence. These data demonstrate that the CACCC element is necessary for GATA-1 promoter transactivation by ME26 virus and that the viral protein may indirectly transactivate the promoter by binding to Sp1.