A c-Myb mutant causes deregulated differentiation due to impaired histone binding and abrogated pioneer factor function

Nucleic Acids Res. 2017 Jul 27;45(13):7681-7696. doi: 10.1093/nar/gkx364.

Abstract

The transcription factor c-Myb is involved in early differentiation and proliferation of haematopoietic cells, where it operates as a regulator of self-renewal and multi-lineage differentiation. Deregulated c-Myb plays critical roles in leukaemias and other human cancers. Due to its role as a master regulator, we hypothesized it might function as a pioneer transcription factor. Our approach to test this was to analyse a mutant of c-Myb, D152V, previously reported to cause haematopoietic defects in mice by an unknown mechanism. Our transcriptome data from K562 cells indicates that this mutation specifically affects c-Myb's ability to regulate genes involved in differentiation, causing failure in c-Myb's ability to block differentiation. Furthermore, we see a major effect of this mutation in assays where chromatin opening is involved. We show that each repeat in the minimal DNA-binding domain of c-Myb binds to histones and that D152V disrupts histone binding of the third repeat. ATAC-seq data indicates this mutation impairs the ability of c-Myb to cause chromatin opening at specific sites. Taken together, our findings support that c-Myb acts as a pioneer factor and show that D152V impairs this function. The D152V mutant is the first mutant of a transcription factor specifically destroying pioneer factor function.

MeSH terms

  • Amino Acid Substitution
  • Animals
  • Cell Differentiation / genetics*
  • Chromatin / genetics
  • Chromatin / metabolism
  • Erythropoiesis / genetics
  • Gene Knockdown Techniques
  • Genes, myb*
  • Histones / metabolism*
  • Humans
  • K562 Cells
  • Mice
  • Models, Molecular
  • Mutant Proteins / chemistry
  • Mutant Proteins / genetics
  • Mutant Proteins / metabolism
  • Mutation*
  • Protein Binding
  • Protein Domains
  • Proto-Oncogene Proteins c-myb / chemistry
  • Proto-Oncogene Proteins c-myb / genetics*
  • Proto-Oncogene Proteins c-myb / metabolism*

Substances

  • Chromatin
  • Histones
  • Mutant Proteins
  • Proto-Oncogene Proteins c-myb