Control of RUNX-induced repression of Notch signaling by MLF and its partner DnaJ-1 during Drosophila hematopoiesis

PLoS Genet. 2017 Jul 25;13(7):e1006932. doi: 10.1371/journal.pgen.1006932. eCollection 2017 Jul.


A tight regulation of transcription factor activity is critical for proper development. For instance, modifications of RUNX transcription factors dosage are associated with several diseases, including hematopoietic malignancies. In Drosophila, Myeloid Leukemia Factor (MLF) has been shown to control blood cell development by stabilizing the RUNX transcription factor Lozenge (Lz). However, the mechanism of action of this conserved family of proteins involved in leukemia remains largely unknown. Here we further characterized MLF's mode of action in Drosophila blood cells using proteomic, transcriptomic and genetic approaches. Our results show that MLF and the Hsp40 co-chaperone family member DnaJ-1 interact through conserved domains and we demonstrate that both proteins bind and stabilize Lz in cell culture, suggesting that MLF and DnaJ-1 form a chaperone complex that directly regulates Lz activity. Importantly, dnaj-1 loss causes an increase in Lz+ blood cell number and size similarly as in mlf mutant larvae. Moreover we find that dnaj-1 genetically interacts with mlf to control Lz level and Lz+ blood cell development in vivo. In addition, we show that mlf and dnaj-1 loss alters Lz+ cell differentiation and that the increase in Lz+ blood cell number and size observed in these mutants is caused by an overactivation of the Notch signaling pathway. Finally, using different conditions to manipulate Lz activity, we show that high levels of Lz are required to repress Notch transcription and signaling. All together, our data indicate that the MLF/DnaJ-1-dependent increase in Lz level allows the repression of Notch expression and signaling to prevent aberrant blood cell development. Thus our findings establish a functional link between MLF and the co-chaperone DnaJ-1 to control RUNX transcription factor activity and Notch signaling during blood cell development in vivo.

MeSH terms

  • Animals
  • Cell Differentiation / genetics
  • DNA-Binding Proteins / genetics*
  • Drosophila Proteins / biosynthesis
  • Drosophila Proteins / genetics*
  • Drosophila melanogaster / genetics
  • Drosophila melanogaster / growth & development
  • Gene Expression Regulation, Developmental
  • HSP40 Heat-Shock Proteins / genetics*
  • Hematopoiesis / genetics*
  • Larva / genetics
  • Larva / growth & development
  • Proteomics
  • Receptors, Notch / biosynthesis
  • Receptors, Notch / genetics*
  • Signal Transduction / genetics
  • Transcription Factors / genetics*


  • DNA-Binding Proteins
  • DnaJ-1 protein, Drosophila
  • Drosophila Proteins
  • HSP40 Heat-Shock Proteins
  • Mlf protein, Drosophila
  • N protein, Drosophila
  • Receptors, Notch
  • Transcription Factors
  • lz protein, Drosophila

Grants and funding

This work was supported by grants from the Agence Nationale de la Recherche (, Fondation ARC (, Ligue Midi Pyrénée contre le Cancer ( and Fédération de Recherche en Biologie de Toulouse ( to LW and in part by grants from the Région Midi-Pyrénées (, Fonds Européen de Développement Régional (FEDER) (, Toulouse Métropole (, and the French Ministry of Research for the Programme Investissement d’Avenir Infrastructures Nationales en Biologie et Santé (PIA, ANR 10-INBS-08, French Proteomics Infrastructure, ProFI; to OBS. MM was supported by fellowships from Université Paul Sabatier ( and Fondation pour la Recherche Médicale ( AC was supported by a fellowship from the China Scholarship Council (CSC; The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.