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Mol. Cell. Biol., 04 1995, 1974-1982, Vol 15, No. 4
S Meyers, N Lenny and SW Hiebert
The AML-1/CBF beta transcription factor complex is targeted by both the
t(8;21) and the inv(16) chromosomal alterations, which are frequently
observed in acute myelogenous leukemia. AML-1 is a site-specific DNA-
binding protein that recognizes the enhancer core motif TGTGGT. The t(8;21)
translocation fuses the first 177 amino acids of AML-1 to MTG8 (also known
as ETO), generating a chimeric protein that retains the DNA- binding domain
of AML-1. Analysis of endogenous AML-1 DNA-binding complexes suggested the
presence of at least two AML-1 isoforms. Accordingly, we screened a human
B-cell cDNA library and isolated a larger, potentially alternatively
spliced, form of AML1, termed AML1B. AML-1B is a protein of 53 kDa that
binds to a consensus AML-1-binding site and complexes with CBF beta.
Subcellular fractionation experiments demonstrated that both AML-1 and
AML-1/ETO are efficiently extracted from the nucleus under ionic conditions
but that AML-1B is localized to a salt-resistant nuclear compartment.
Analysis of the transcriptional activities of AML-1, AML-1B, and AML-1/ETO
demonstrated that only AML- 1B activates transcription from the T-cell
receptor beta enhancer. Mixing experiments indicated that AML-1/ETO can
efficiently block AML- 1B-dependent transcriptional activation, suggesting
that the t(8;21) translocation creates a dominant interfering protein.
Copyright © 1995, American Society for Microbiology
The t(8;21) fusion protein interferes with AML-1B-dependent transcriptional activation
Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105.
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