x chromosome sites autonomously recruit the dosage compensation complex in drosophila malesx染色体网站自主招收雄性果蝇的剂量补偿复杂.pdf

Open access, freely available online PLoS BIOLOGY X Chromosome Sites Autonomously Recruit the Dosage Compensation Complex in Drosophila Males * Delphine Fagegaltier, Bruce S. Baker Department of Biological Sciences, Stanford University, Stanford, California, United States of America 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. Citation: Fagegaltier D, Baker BS (2004) X chromosome sites autonomously recruit the dosage compensation complex in Drosophila males. PLoS Biol 2(11): e341. Introduction