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Yeast X‐chromosome‐associated protein 5 (Xap5) functions with H2A.Z to suppress aberrant transcripts

Shajahan Anver, Assen Roguev, Martin Zofall, Nevan J Krogan, Shiv I S Grewal, Stacey L Harmer

Author Affiliations

  1. Shajahan Anver14,
  2. Assen Roguev2,
  3. Martin Zofall3,
  4. Nevan J Krogan2,
  5. Shiv I S Grewal3 and
  6. Stacey L Harmer*,1
  1. 1Department of Plant Biology, College of Biological Sciences University of California, Davis, CA, USA
  2. 2Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, USA
  3. 3Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
  4. 4Max Plank Institute for Plant Breeding Research, Cologne, Germany
  1. *Corresponding author. Tel: +1 530 752 8101; E‐mail: slharmer{at}
View Abstract


Chromatin regulatory proteins affect diverse developmental and environmental response pathways via their influence on nuclear processes such as the regulation of gene expression. Through a genome‐wide genetic screen, we implicate a novel protein called X‐chromosome‐associated protein 5 (Xap5) in chromatin regulation. We show that Xap5 is a chromatin‐associated protein acting in a similar manner as the histone variant H2A.Z to suppress expression of antisense and repeat element transcripts throughout the fission yeast genome. Xap5 is highly conserved across eukaryotes, and a plant homolog rescues xap5 mutant yeast. We propose that Xap5 likely functions as a chromatin regulator in diverse organisms.


Embedded Image

Xap5 is a conserved protein of unknown function. This study shows that fission yeast Xap5 binds chromatin and cooperates with histone variant H2A.Z to suppress expression of antisense and repeat element transcripts.

  • Antisense transcripts and repeat elements are upregulated in Δxap5 and Δpht1 mutants and are synergistically overexpressed in Δxap5Δpht1 double mutants.

  • Xap5 associates with chromatin both at genic and at intergenic regions and is enriched at transposable elements and other repeated loci.

  • The Arabidopsis Xap5 homolog rescues xap5 mutant yeast, indicating that Xap5 function is conserved in diverse eukaryotes.

  • Received April 11, 2014.
  • Revision received May 15, 2014.
  • Accepted May 21, 2014.
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