title: Direct protein interactions are responsible for Ikaros-GATA and Ikaros-Cdk9 cooperativeness in hematopoietic cells.
abstract: Ikaros (Ik) is a critical regulator of hematopoietic gene expression. Here, we established that the Ik interactions with GATA transcription factors and cyclin-dependent kinase 9 (Cdk9), a component of the positive transcription elongation factor b (P-TEFb), are required for transcriptional activation of Ik target genes. A detailed dissection of Ik-GATA and Ik-Cdk9 protein interactions indicated that the C-terminal zinc finger domain of Ik interacts directly with the C-terminal zinc fingers of GATA1, GATA2, and GATA3, whereas the N-terminal zinc finger domain of Ik is required for interaction with the kinase and T-loop domains of Cdk9. The relevance of these interactions was demonstrated in vivo in COS-7 and primary hematopoietic cells, in which Ik facilitated Cdk9 and GATA protein recruitment to gene promoters and transcriptional activation. Moreover, the oncogenic isoform Ik6 did not efficiently interact with Cdk9 or GATA proteins in vivo and perturbed Cdk9/P-TEFb recruitment to Ik target genes, thereby affecting transcription elongation. Finally, characterization of a novel nuclear Ik isoform revealed that Ik exon 6 is dispensable for interactions with Mi2 and GATA proteins but is essential for the Cdk9 interaction. Thus, Ik is central to the Ik-GATA-Cdk9 regulatory network, which is broadly utilized for gene regulation in hematopoietic cells.
authors.affiliation: Maisonneuve-Rosemont Hospital Research Center, Maisonneuve-Rosemont Hospital, and Department of Medicine, University of Montreal, Montreal, Quebec, Canada.
authors.forename: Stefania
authors.initials: S
authors.lastname: Bottardi
authors.forename: Lionel
authors.initials: L
authors.lastname: Mavoungou
authors.forename: Vincent
authors.initials: V
authors.lastname: Bourgoin
authors.forename: Nazar
authors.initials: N
authors.lastname: Mashtalir
authors.forename: El Bachir
authors.initials: el B
authors.lastname: Affar
authors.forename: Eric
authors.initials: E
authors.lastname: Milot
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D042863:Cyclin-Dependent Kinase 9 / Q000737:chemistry / Q000378:metabolism*; D050982:GATA1 Transcription Factor / Q000737:chemistry / Q000378:metabolism*; D050989:GATA2 Transcription Factor / Q000737:chemistry / Q000378:metabolism*; D050990:GATA3 Transcription Factor / Q000737:chemistry / Q000378:metabolism*; D006410:Hematopoiesis; D051740:Ikaros Transcription Factor / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D054730:Protein Interaction Domains and Motifs; D060066:Protein Interaction Maps; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D050982:GATA1 Transcription Factor; D050989:GATA2 Transcription Factor; D050990:GATA3 Transcription Factor; C494689:Gata1 protein, mouse; C494748:Gata3 protein, mouse; D020033:Protein Isoforms; C497238:Zfpn1a1 protein, mouse; D051740:Ikaros Transcription Factor; D042863:Cyclin-Dependent Kinase 9