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.
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.