Changes in chromosome number impair fitness by disrupting the balance of gene expression. Here we analyze mechanisms to compensate for changes in gene dose that accompanied the evolution of sex chromosomes from autosomes. Using single-copy transgenes integrated throughout the Caenorhabditis elegans genome, we show that expression of all X-linked transgenes is balanced between XX hermaphrodites and XO males. However, proximity of a dosage compensation complex (DCC) binding site (rex site) is neither necessary to repress X-linked transgenes nor sufficient to repress transgenes on autosomes. Thus, X is broadly permissive for dosage compensation, and the DCC acts via a chromosome-wide mechanism to balance transcription between sexes. In contrast, no analogous X-chromosome-wide mechanism balances transcription between X and autosomes: expression of compensated hermaphrodite X-linked transgenes is half that of autosomal transgenes. Furthermore, our results argue against an X-chromosome dosage compensation model contingent upon rex-directed positioning of X relative to the nuclear periphery.
SRR023579.sraPublicly available at the Sequence Read Archive + (accession no: GSE20136).
Transcriptome Analysis of roundwormPublicly available at the NCBI Short Read Archive (accession no: GSE20136).
Condensin Controls Recruitment of RNA Polymerase II to Achieve X-Chromosome Dosage CompensationPublicly availale at the NCBI Gene Expression Omnibus (accession no: GSE43087).
SRR031122.sraPublicly available at the Sequence Read Archive + (accession no: GSE20136).
SRR031123.sraPublicly available at the Sequence Read Archive + (accession no: GSE20136).
Condensin-Driven Remodeling of X-Chromosome Topology during Dosage CompensationPublicly available at the NCBI Gene Expression Omnibus (accession no: GSE59716).
- Barbara J Meyer
- Barbara J Meyer
- Bayly S Wheeler
- Christian Frøkjær-Jensen
- Erik Jorgensen
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Edith Heard, Institut Curie, France
© 2016, Wheeler et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.