A Testis-Specific Chaperone and the Chromatin Remodeler ISWI Mediate Repackaging of the Paternal Genome

Cell Rep. 2015 Nov 17;13(7):1310-1318. doi: 10.1016/j.celrep.2015.10.010. Epub 2015 Nov 5.


During spermatogenesis, the paternal genome is repackaged into a non-nucleosomal, highly compacted chromatin structure. Bioinformatic analysis revealed that Drosophila sperm chromatin proteins are characterized by a motif related to the high-mobility group (HMG) box, which we termed male-specific transcript (MST)-HMG box. MST77F is a MST-HMG-box protein that forms an essential component of sperm chromatin. The deposition of MST77F onto the paternal genome requires the chaperone function of tNAP, a testis-specific NAP protein. MST77F, in turn, enables the stable incorporation of MST35Ba and MST35Bb into sperm chromatin. Following MST-HMG-box protein deposition, the ATP-dependent chromatin remodeler ISWI mediates the appropriate organization of sperm chromatin. Conversely, at fertilization, maternal ISWI targets the paternal genome and drives its repackaging into de-condensed nucleosomal chromatin. Failure of this transition in ISWI mutant embryos is followed by mitotic defects, aneuploidy, and haploid embryonic divisions. Thus, ISWI enables bi-directional transitions between two fundamentally different forms of chromatin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / chemistry
  • Adenosine Triphosphatases / physiology*
  • Animals
  • Chromatin / metabolism
  • Chromatin Assembly and Disassembly
  • Chromosomes, Insect / genetics
  • Chromosomes, Insect / metabolism
  • Drosophila Proteins / chemistry
  • Drosophila Proteins / metabolism
  • Drosophila melanogaster
  • Genome, Insect*
  • Histones / chemistry
  • Histones / metabolism
  • Male
  • Mitosis
  • Protein Binding
  • Spermatozoa / physiology
  • Testis / metabolism
  • Testis / ultrastructure*
  • Transcription Factors / chemistry
  • Transcription Factors / physiology*


  • Chromatin
  • Drosophila Proteins
  • Histones
  • ISWI protein
  • Mst77F protein, Drosophila
  • Transcription Factors
  • Adenosine Triphosphatases