Ikaros antagonizes DNA binding by STAT5 in pre-B cells

PLoS One. 2020 Nov 12;15(11):e0242211. doi: 10.1371/journal.pone.0242211. eCollection 2020.

Abstract

The IKZF1 gene, which encodes the Ikaros transcription factor, is frequently deleted or mutated in patients with B-cell precursor acute lymphoblastic leukemias that express oncogenes, like BCR-ABL, which activate the JAK-STAT5 pathway. Ikaros functionally antagonizes the transcriptional programs downstream of IL-7/STAT5 during B cell development, as well as STAT5 activity in leukemic cells. However, the mechanisms by which Ikaros interferes with STAT5 function is unknown. We studied the genomic distribution of Ikaros and STAT5 on chromatin in a murine pre-B cell line, and found that both proteins colocalize on >60% of STAT5 target regions. Strikingly, Ikaros activity leads to widespread loss of STAT5 binding at most of its genomic targets within two hours of Ikaros induction, suggesting a direct mechanism. Ikaros did not alter the level of total or phosphorylated STAT5 proteins, nor did it associate with STAT5. Using sequences from the Cish, Socs2 and Bcl6 genes that Ikaros and STAT5 target, we show that both proteins bind overlapping sequences at GGAA motifs. Our results demonstrate that Ikaros antagonizes STAT5 DNA binding, in part by competing for common target sequences. Our study has implications for understanding the functions of Ikaros and STAT5 in B cell development and transformation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Cell Line
  • Chromatin / metabolism
  • DNA / chemistry
  • DNA / metabolism*
  • Ikaros Transcription Factor / deficiency
  • Ikaros Transcription Factor / genetics
  • Ikaros Transcription Factor / metabolism*
  • Interleukin-17 / pharmacology
  • Mice
  • Mice, Knockout
  • Phosphorylation
  • Precursor Cells, B-Lymphoid / cytology
  • Precursor Cells, B-Lymphoid / metabolism*
  • Protein Binding
  • STAT5 Transcription Factor / genetics
  • STAT5 Transcription Factor / metabolism*
  • Suppressor of Cytokine Signaling Proteins / chemistry
  • Suppressor of Cytokine Signaling Proteins / metabolism
  • Up-Regulation / drug effects

Substances

  • Chromatin
  • Interleukin-17
  • STAT5 Transcription Factor
  • Socs2 protein, mouse
  • Suppressor of Cytokine Signaling Proteins
  • Zfpn1a1 protein, mouse
  • cytokine inducible SH2-containing protein
  • Ikaros Transcription Factor
  • DNA

Grants and funding

This work was supported by grants from Fondation ARC (https://www.fondation-arc.org) (to BH), Fondation de France (https://www.fondationdefrance.org) (to SC), Institut National du Cancer (https://www.e-cancer.fr) (#2015-114, to PK), Ligue Nationale Contre le Cancer (https://www.ligue-cancer.net) (équipe labellisée, to SC) and by the grant ANR-10-LABX-0030-INRT, a French State fund managed by the Agence Nationale de la Recherche (https://anr.fr) under the framework program Investissements d’Avenir ANR-10-IDEX-0002-02. BH was supported by a postdoctoral fellowship from the Fondation de France (https://www.fondationdefrance.org), and CS by a predoctoral fellowship from the Ligue Nationale Contre le Cancer (https://www.ligue-cancer.net). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.