A short Gfi-1B isoform controls erythroid differentiation by recruiting the LSD1–CoREST complex through the dimethylation of its SNAG domain

Benoît Laurent,Michaela Fontenay,Isabelle Dusanter-Fourt,Eric Soler,Dominique Duménil,Charlotte Andrieu-Soler,Voahangy Randrianarison-Huetz,Emilie Frisan

doi:10.1242/jcs.095877

Abstract

Gfi-1B is a transcriptional repressor essential for the regulation of erythropoiesis and megakaryopoiesis. Here we identify Gfi-1B p32, a Gfi-1B isoform, as essential for erythroid differentiation. Gfi-1B p32 is generated by alternative splicing and lacks the two first zinc finger domains of the protein. Selective knock down of Gfi-1B p32 compromises erythroid differentiation, whereas its ectopic expression induces erythropoiesis in the absence of erythropoietin. Gfi-1B p32 isoform binds to Gfi-1B target gene promoters and associates with the LSD1-CoREST repressor complex more efficiently than the major Gfi-1B p37 isoform. Furthermore, we show that Gfi-1B includes a KSKK motif in its SNAG domain, which recruits the repressor complex only when dimethylated on lysine 8. Mutation of lysine 8 prevents Gfi-1B p32-induced erythroid development. Our results thus highlight a key role for the alternatively spliced Gfi-1B p32 isoform in erythroid development.

Highlights

Hematopoiesis is dependent on the proper regulation of selfrenewal, proliferation and differentiation of stem cells from which all hematopoietic lineages originate
We further showed that this Gfi-1B p32 isoform efficiently recruits the LSD1–CoREST complex to Gfi-1B target gene promoters, and that such recruitment relies on the dimethylation of a lysine residue located at position 8 in its SNAG domain
An alternative spliced Gfi-1B transcript was recently described in peripheral blood mononuclear cells (PBMC) of patients with myeloid leukemia (Vassen et al, 2005)

Summary

Introduction

Hematopoiesis is dependent on the proper regulation of selfrenewal, proliferation and differentiation of stem cells from which all hematopoietic lineages originate. These processes are tightly regulated and involve coordinated activation of specific genes and silencing of others. Gfi-1B plays a crucial role in the repression of gene transcription in hematopoietic stem cell (Khandanpour et al, 2010) and during erythroid and megakaryocytic development (Garcon et al, 2005; Osawa et al, 2002; Randrianarison-Huetz et al, 2010; Saleque et al, 2002; van der Meer et al, 2010). It was suggested that Gfi-1B might play a role in oncogenesis: the human GFI1B gene was mapped at chromosomes 9q34.13, a region translocated to chromosome 22 generating the ‘Philadelphia chromosome’

Methods

Results

Discussion

Conclusion