The key protein complex PRC2 was discovered decades ago to silence genes, but new findings by Frederic Berger and his group at the Gregor Mendel Institute show that PRC2 represses transposons in a range of eukaryotes and only gradually evolved to silence genes. The study was published on September 21 in the journal Current Biology.
with researchers at Freie Universität Berlin, University of Cambridge, Nantes University, the National Institute of Genetics and Monash University, investigated how PRC2 acts in a range of eukaryotes.
To understand PRC2's role in the ancestors of eukaryotes, the researchers studied the genomes of three widely distant lineages of eukaryotes: plants, SAR and ophistokonts, the lineage to which humans and fungi belong. All of these eukaryotes contain transposons, mobile genetic elements that can excise themselves from DNA and insert at novel locations—ato genome stability, hence why transposons have to be silenced. In mutant diatoms, bryophytes and red algae the removal of PRC2 activity caused the loss of silencing of transposable elements .
"These findings show that PRC2 represses transposable elements in these distant lineages, which defines this as a function that arose in the ancestor all three lineages. PRC2's origin was likely to primarily defend the genome from invasion by transposons. This ancestral function is a profound change in paradigm," says Frederic Berger, group leader at GMI and the study's corresponding author.
Over the course of evolution, however, the function of PRC2 gradually shifted from repressing transposons to repressing