Multiple subnuclear targeting signals of the leukemia-related AML1/ETO and ETO repressor proteins
Department of Cell Biology
Medical Subject Headings
Binding Sites; Chromosomes, Human, Pair 21; Chromosomes, Human, Pair 8; Core Binding Factor Alpha 2 Subunit; DNA, Neoplasm; DNA-Binding Proteins; Humans; Hydrophobicity; Leukemia, Myeloid, Acute; Microscopy, Fluorescence; Oncogene Proteins, Fusion; Protein Sorting Signals; Protein Structure, Tertiary; Protein Transport; *Proto-Oncogene Proteins; Recombinant Fusion Proteins; Repressor Proteins; Structure-Activity Relationship; Subcellular Fractions; Transcription Factors; Transfection; Translocation, Genetic; Tumor Cells, Cultured; Zinc Fingers
Cell Biology | Life Sciences | Medicine and Health Sciences
Leukemic disease can be linked to aberrant gene expression. This often is the result of molecular alterations in transcription factors that lead to their misrouting within the nucleus. The acute myelogenous leukemia-related fusion protein AML1ETO is a striking example. It originates from a gene rearrangement t(8;21) that fuses the N-terminal part of the key hematopoietic regulatory factor AML1 (RUNX1) to the ETO (MTG8) repressor protein. AML1ETO lacks the intranuclear targeting signal of the wild-type AML1 and is directed by the ETO component to alternate nuclear matrix-associated sites. To understand this aberrant subnuclear trafficking of AML1ETO, we created a series of mutations in the ETO protein. These were characterized biochemically by immunoblotting and in situ by immunofluorescence microscopy. We identified two independent subnuclear targeting signals in the N- and C-terminal regions of ETO that together direct ETO to the same binding sites occupied by AML1ETO. However, each segment alone is targeted to a different intranuclear location. The N-terminal segment contains a nuclear localization signal and the conserved hydrophobic heptad repeat domain responsible for protein dimerization and interaction with the mSin3A transcriptional repressor. The C-terminal segment spans the nervy domain and the zinc finger region, which together support interactions with the corepressors N-CoR and HDACs. Our findings provide a molecular basis for aberrant subnuclear targeting of the AML1ETO protein, which is a principal defect in t(8;21)-related acute myelogenous leukemia.
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Citation: Proc Natl Acad Sci U S A. 2002 Nov 26;99(24):15434-9. Epub 2002 Nov 11. Link to article on publisher's site