ETO, fusion partner in t(8;21) acute myeloid leukemia, represses transcription by interaction with the human N-CoR/mSin3/HDAC1 complex

Abstract

The t(8;21) translocation between two genes known as AML1 and ETO is seen in approximately 12-15% of all acute myeloid leukemia (AML) and is the second-mostfrequently observed nonrandom genetic alteration associated with AML. AML1 up-regulates a number of target genes critical to normal hematopoiesis, whereas the AML1͞ETO fusion interferes with this trans-activation. We discovered that the fusion partner ETO binds to the human homolog of the murine nuclear receptor corepressor (N-CoR). The interaction is mediated by two unusual zinc finger motifs present at the carboxyl terminus of ETO. Human N-CoR (HuN-CoR), which we cloned and sequenced in its entirety, encodes a 2,440-amino acid polypeptide and has a central domain that binds ETO. N-CoR, mammalian Sin3 (mSin3A and B), and histone deacetylase 1 (HDAC1) form a complex that alters chromatin structure and mediates transcriptional repression by nuclear receptors and by a number of oncoregulatory proteins. We found that ETO, through its interaction with the N-CoR͞mSin3͞HDAC1 complex, is also a potent repressor of transcription. This observation provides a mechanism for how the AML1͞ETO fusion may inhibit expression of AML1-responsive target genes and disturb normal hematopoiesis.

The adenovirus E1A binding protein BS69 is a corepressor of transcription through recruitment of N-CoR

“…Since the MYND domain is a putative interaction molecule for the nuclear co-repressors N-CoR and SMRT (Lutterbach et al, 1998a;Gelmetti et al, 1998;Wang et al, 1998) we tested whether the MYND domain of BS69 also mediates N-CoR binding in a coimmunoprecipitation experiment. We transfected human U2OS osteosarcoma cells with expression vectors for FLAG tagged N-CoR and full-length human BS69 fused to the DNA binding domain of the yeast transcription factor GAL4 at the N-terminus ( Figure 2).…”

“…The C-terminus harbours a region with homology to the MYND domain, a two zinc ®nger motif ®rst identi®ed in DEAF-1 (Gross and McGinnis, 1996) and in MTG8/ETO (Lutterbach et al, 1998a). This domain was shown to be required for both repression of basal transcription by the AML/ETO fusion protein and binding of the transcriptional corepressors N-CoR and SMRT (Lutterbach et al, 1998b;Gelmetti et al, 1998;Wang et al, 1998). N-CoR and its close homologue SMRT were cloned as co-repressors of the thyroidhormone and retinoic acid receptors (Chen and Evans, 1995;Horlein et al, 1995).…”

ELA2 is regulated by hematopoietic transcription factors, but not repressed by AML1-ETO

“…The resulting AML1-ETO fusion protein is expressed in E12% of AML of the M2 subtype (Look, 1997). AML1-ETO has been shown to interact with a number of proteins present in corepressor complexes, suggesting that AML1-ETO may act as a transcriptional repressor (Meyers et al, 1995;Gelmetti et al, 1998;Lutterbach et al, 1998;Wang et al, 1998;Westendorf et al, 1998;Amann et al, 2001;Hildebrand et al, 2001;Zhang et al, 2001;Linggi et al, 2002;Lausen et al, 2004). However, there have been very few studies that correlate a DNA binding event by AML1-ETO at a target gene's promoter with a direct consequence on transcription (see, e.g.…”

Cell type dependent regulation of multidrug resistance-1 gene expression by AML1-ETO

“…Indeed, AML1-ETO has been shown to act as a dominant negative inhibitor of AML1 [50]. Multiple repressors of transcription, such as Sin3A, HDAC, N-CoR, and SMRT, interact with the ETO portion of the fusion protein [17][18][19][20], which provides the molecular mechanisms of repression. AML1-ETO has been reported to repress the MDR1 promoter in hematopoietic HEL cells and non-hematopoietic C33A cells [26].…”

“…Furthermore, reporter-gene assays and protein-protein interaction data provide a further molecular mechanism for this effect. AML1-ETO binds to transcription repressor complexes, such as NCoR, Sin3A, SMRT, and class 1 histone deacetylases (HDACs), which actively shut down transcription from AML1 responsive promoters [15][16][17][18][19][20]. However, AML1-ETO does not always function as a transcriptional repressor.…”