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Mol. Cell. Biol., May 1995, 2383-2392, Vol 15, No. 5
T Tanaka, K Mitani, M Kurokawa, S Ogawa, K Tanaka, J Nishida, Y Yazaki, Y Shibata and H Hirai
The chromosomal translocation t(3;21)(q26;q22), which is found in blastic
crisis in chronic myelogenous leukemias and myelodysplastic
syndrome-derived leukemias, produces AML1/Evi-1 chimeric transcription
factor and is thought to play important roles in acute leukemic
transformation of hemopoietic stem cells. We report here the functional
analyses of AML1/Evi-1. It was revealed that AML1/Evi-1 itself does not
alter the transactivation level through mouse polyomavirus enhancer-
binding protein 2 (PEBP2; PEA2) sites (binding site of AML1) but dominantly
suppresses the transactivation by intact AML1, which is assumed to be a
stimulator of myeloid cell differentiation. DNA-binding competition is a
putative mechanism of such dominant negative effects of AML1/Evi-1 because
it binds to PEBP2 sites with higher affinity than AML1 does. Furthermore,
AML1/Evi-1 stimulated c-fos promoter transactivation and increased AP-1
activity, as Evi-1 (which is not normally expressed in hemopoietic cells)
did. Experiments using deletion mutants of AML1/Evi-1 showed that these two
functions are mutually independent because the dominant negative effects on
intact AML1 and the stimulation of AP-1 activity are dependent on the runt
domain (DNA-binding domain of AML1) and the zinc finger domain near the C
terminus, respectively. Furthermore, we showed that AML1/Evi-1 blocks
granulocytic differentiation, otherwise induced by granulocyte colony-
stimulating factor, of 32Dcl3 myeloid cells. It was also suggested that
both AML1-derived and Evi-1-derived portions of the fusion protein play
crucial roles in this differentiation block. We conclude that the leukemic
cell transformation in t(3;21) leukemias is probably caused by these dual
functions of AML1/Evi-1 chimeric protein.
Copyright © 1995, American Society for Microbiology
Dual functions of the AML1/Evi-1 chimeric protein in the mechanism of leukemogenesis in t(3;21) leukemias
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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