X chromosome sites autonomously recruit the dosage compensation complex in Drosophila males

PLoS Biol. 2004 Nov;2(11):e341. doi: 10.1371/journal.pbio.0020341. Epub 2004 Oct 5.


It has been proposed that dosage compensation in Drosophila males occurs by binding of two core proteins, MSL-1 and MSL-2, to a set of 35-40 X chromosome "entry sites" that serve to nucleate mature complexes, termed compensasomes, which then spread to neighboring sequences to double expression of most X-linked genes. Here we show that any piece of the X chromosome with which compensasomes are associated in wild-type displays a normal pattern of compensasome binding when inserted into an autosome, independently of the presence of an entry site. Furthermore, in chromosomal rearrangements in which a piece of X chromosome is inserted into an autosome, or a piece of autosome is translocated to the X chromosome, we do not observe spreading of compensasomes to regions of autosomes that have been juxtaposed to X chromosomal material. Taken together these results suggest that spreading is not involved in dosage compensation and that nothing distinguishes an entry site from the other X chromosome sites occupied by compensasomes beyond their relative affinities for compensasomes. We propose a new model in which the distribution of compensasomes along the X chromosome is achieved according to the hierarchical affinities of individual binding sites.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Binding Sites
  • Chromosomes / ultrastructure
  • Crosses, Genetic
  • DNA-Binding Proteins / genetics
  • Dosage Compensation, Genetic*
  • Drosophila / genetics*
  • Drosophila Proteins / genetics
  • Female
  • Genotype
  • In Situ Hybridization
  • Male
  • Microscopy, Fluorescence
  • Nuclear Proteins / genetics
  • Protein Binding
  • Sex Factors
  • Transcription Factors / genetics
  • Translocation, Genetic
  • X Chromosome / genetics*
  • X Chromosome / ultrastructure*


  • DNA-Binding Proteins
  • Drosophila Proteins
  • Nuclear Proteins
  • Transcription Factors
  • msl-1 protein, Drosophila
  • msl-2 protein, Drosophila
  • msl-3 protein, Drosophila