Multivalent binding of the ETO corepressor to E proteins facilitates dual repression controls targeting chromatin and the basal transcription machinery.
E proteins are a family of helix-loop-helix transcription factors that play important roles in cell differentiation and homeostasis. They contain at least two activation domains, AD1 and AD2. ETO family proteins and the leukemogenic AML1-ETO fusion protein are corepressors of E proteins. It is thought that ETO represses E-protein activity by interacting with AD1, which competes away p300/CBP histone acetyltransferases. Here we report that E proteins contain another conserved ETO-interacting region, termed DES, and that differential associations with AD1 and DES allow ETO to repress transcription through both chromatin-dependent and chromatin-independent mechanisms. At the chromatin level, AD1 and AD2 cooperatively recruit p300. ETO interacts with AD1 to abolish p300 recruitment and to allow HDAC-dependent silencing. At the post-chromatin-remodeling level, binding to DES enables ETO to directly inhibit activation of the basal transcription machinery. This novel repression mechanism is conserved in ETO family proteins and in the AML1-ETO fusion protein. In addition, the repression capacity exerted by each mechanism is differentially modulated by cross talk among various ETO domains and the AML1 domain of AML1-ETO. In particular, the oligomerization domain of ETO plays a major role in targeting ETO to the DES region and independently potentiates the TAFH domain-mediated AD1 interaction. The ability to exert repression at different levels not only may allow these corepressors to impose robust inhibition of signal-independent transcription but may also allow a rapid response to signals. In addition, our newly defined domain interactions and their interplays have important implications in effectively targeting both E-protein fusion proteins and AML1-ETO found in cancers.
Guo
Chun
C
Department of Cancer and Cell Biology, Vontz Center for Molecular Studies, University of Cincinnati College of Medicine, 3125 Eden Avenue, Cincinnati, OH 45267-0521, USA.
Hu
Qiande
Q
Yan
Chunxia
C
Zhang
Jinsong
J
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002843:Chromatin / Q000378:metabolism*; D050676:Core Binding Factor Alpha 2 Subunit / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D008958:Models, Molecular; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D000075142:RUNX1 Translocation Partner 1 Protein; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D051792:Basic Helix-Loop-Helix Proteins; D002843:Chromatin; D050676:Core Binding Factor Alpha 2 Subunit; D011518:Proto-Oncogene Proteins; D000075142:RUNX1 Translocation Partner 1 Protein; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C493728:RUNX1 protein, human; C082222:RUNX1T1 protein, human