The Caenorhabditis elegans dosage compensation machinery is recruited to X chromosome DNA attached to an autosome.
The dosage compensation machinery of Caenorhabditis elegans is targeted specifically to the X chromosomes of hermaphrodites (XX) to reduce gene expression by half. Many of the trans-acting factors that direct the dosage compensation machinery to X have been identified, but none of the proposed cis-acting X chromosome-recognition elements needed to recruit dosage compensation components have been found. To study X chromosome recognition, we explored whether portions of an X chromosome attached to an autosome are competent to bind the C. elegans dosage compensation complex (DCC). To do so, we devised a three-dimensional in situ approach that allowed us to compare the volume, position, and number of chromosomal and subchromosomal bodies bound by the dosage compensation machinery in wild-type XX nuclei and XX nuclei carrying an X duplication. The dosage compensation complex was found to associate with a duplication of the right 30% of X, but the complex did not spread onto adjacent autosomal sequences. This result indicates that all the information required to specify X chromosome identity resides on the duplication and that the dosage compensation machinery can localize to a site distinct from the full-length hermaphrodite X chromosome. In contrast, smaller duplications of other regions of X appeared to not support localization of the DCC. In a separate effort to identify cis-acting X recognition elements, we used a computational approach to analyze genomic DNA sequences for the presence of short motifs that were abundant and overrepresented on X relative to autosomes. Fourteen families of X-enriched motifs were discovered and mapped onto the X chromosome.
Lieb
J D
JD
Howard Hughes Medical Institute and University of California, Berkeley, California 94720-3204, USA.
de Solorzano
C O
CO
Rodriguez
E G
EG
Jones
A
A
Angelo
M
M
Lockett
S
S
Meyer
B J
BJ
D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins / Q000502:physiology; D018797:Cell Cycle Proteins / Q000502:physiology; D002467:Cell Nucleus / Q000648:ultrastructure; D002868:Chromosomal Proteins, Non-Histone / Q000502:physiology; D002875:Chromosomes / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000502:physiology; D012734:Disorders of Sex Development / Q000235:genetics*; D004303:Dosage Compensation, Genetic; D047108:Embryonic Development; D020440:Gene Duplication; D005786:Gene Expression Regulation; D015801:Helminth Proteins / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D046911:Macromolecular Substances; D018613:Microscopy, Confocal; D009687:Nuclear Proteins / Q000502:physiology; D014178:Translocation, Genetic; D014960:X Chromosome / Q000235:genetics*
D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; C090454:DPY-27 protein, C elegans; D015801:Helminth Proteins; C110487:MIX-1 protein, C elegans; D046911:Macromolecular Substances; D009687:Nuclear Proteins; C079666:Sdc-3 protein, C elegans; C096340:dpy-30 protein, C elegans