Oligomerization of Evi-1 regulated by the PR domain contributes to recruitment of corepressor CtBP

Abstract

Evi-1 is a transcription factor that is implicated in leukemic transformation of hematopoietic cells. Two distinct alternative forms, Evi-1a and Evi-1c, are generated from the EVI-1 gene. Whereas Evi-1a is widely recognized as an oncoprotein, a role for Evi-1c, which has an additional PR domain in the amino-terminus of Evi-1a, in leukemogenesis, has not been elucidated thus far. Aberrant oligomerization of transcription factors has recently emerged as a prevalent mechanism for activating their oncogenic potential in hematopoietic malignancies. Here, to study the mechanisms that underlie Evi-1-mediated oncogenesis, we investigated formation of oligomeric complexes by the Evi-1 proteins. We show that Evi-1a forms homo-oligomers, whereas Evi-1c exclusively exists as a monomer in mammalian cells. Remarkably, Evi-1c has lost the ability to interact with CtBP, a transcriptional corepressor that associates with Evi-1a. As a consequence, the ability of Evi-1c to repress transforming growth factor-b (TGF-b) signaling is significantly abrogated. These results identify a novel function of a PR domain to regulate oligomerization of transcription factors and suggest that homo-oligomerization may play a critical role in corepressor recruitment by the Evi-1 proteins. In addition, we found that the chimeric oncoprotein acute myelocytic leukemia (AML)1-Evi-1, generated in t(3;21) leukemia, also forms homo-oligomers and hetero-oligomers with Evi-1a, while it did not interact with Evi-1c. Consistent with the results, repression of TGF-b by AML1-Evi-1 was significantly enhanced by Evi-1a, whereas it was hardly affected by the presence of Evi-1c. These results suggest that oligomerization may contribute to the oncogenic potential of Evi-1-containing proteins.

C. elegansEVI1 proto-oncogene, EGL-43, is necessary for Notch-mediated cell fate specification and regulates cell invasion

“…We expected this PR domain-YFP protein to be a dominant-negative form of EGL-43 because the PR domain regulates the oligomerization of the EVI1 protein (Nitta et al, 2005), and EVI1 protein variants lacking the PR domain can cause leukemia (Fears et al, 1996;Morishita et al, 1988). AC invasion was defective (60%, 26 of 43) when PR-YFP expression was driven by the wild-type regulatory region of egl-43 (Fig.…”

Pbx1 is a downstream target of Evi-1 in hematopoietic stem/progenitors and leukemic cells

“…The plasmid pME18S-EVI-1 (human) (Tanaka et al, 1994;Nitta et al, 2005), various EVI-1 mutants inserted in pME18S (Tanaka et al, 1994;Kurokawa et al, 1998;Izutsu et al, 2001), pMXs-neo-E2A/HLF (a gift from T Inaba), FLAGtagged-AML1/ETO (a gift from SW Hiebert) (Meyers et al, 1993) inserted in pMSCV-neo (Clontech, Mountain view, CA, USA) , have been described earlier.…”

“…The ecotropic viral integration site-1 (Evi-1) gene is a member of the SET/PR domain family of transcription factors (Fears et al, 1996;Nitta et al, 2005). It has been shown to interact with several transcriptional regulators like Smad3, CtBP, and PU.1, to mediate transcription (Kurokawa et al, 1998;Izutsu et al, 2001;LaricchiaRobbio et al, 2009).…”

EVI-1 interacts with histone methyltransferases SUV39H1 and G9a for transcriptional repression and bone marrow immortalization

“…12,14 The pCMV-Myc-SUV39H1 and pEGFPC1-G9a were gifts from M Tachibana and Y Shinkai. SUV39H1-H324K was created by PCR mutagenesis to change amino acid 324 from histidine to lysine.…”

“…Although related, functional differences between EVI-1 and MDS1-EVI-1 have been documented. 14,15 In addition to its DNA-binding activity, EVI-1 has the potential to recruit diverse proteins, such as Smad3, HDACs and CtBP, 5,[16][17][18] thus generating complexes for transcriptional regulation.…”