title: X chromosome sites autonomously recruit the dosage compensation complex in Drosophila males.
abstract: 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.
authors.affiliation: Department of Biological Sciences, Stanford University, Stanford, California, USA.
authors.forename: Delphine
authors.initials: D
authors.lastname: Fagegaltier
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Baker
mesh_terms: D000818:Animals; D001665:Binding Sites; D002875:Chromosomes / Q000648:ultrastructure; D003433:Crosses, Genetic; D004268:DNA-Binding Proteins / Q000235:genetics; D004303:Dosage Compensation, Genetic; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics; D005260:Female; D005838:Genotype; D017403:In Situ Hybridization; D008297:Male; D008856:Microscopy, Fluorescence; D009687:Nuclear Proteins / Q000235:genetics; D011485:Protein Binding; D012737:Sex Factors; D014157:Transcription Factors / Q000235:genetics; D014178:Translocation, Genetic; D014960:X Chromosome / Q000235:genetics* / Q000648:ultrastructure*
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; C082132:msl-1 protein, Drosophila; C094166:msl-2 protein, Drosophila; C093904:msl-3 protein, Drosophila