“Revolutionary Shift in Understanding: New Insights into the Fundamental Role of a Key Gene Regulator”

by Hiroshi Tanaka
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PRC2 gene regulation

Recent discoveries have significantly altered the understanding of the Polycomb repressive complex 2 (PRC2), shifting its perceived role from governing developmental genes to defending the genome against transposon incursions. This fundamental role, consistent across a range of eukaryotes, has gradually evolved, leading to PRC2’s modern function in the repression of protein-coding genes, especially evident in flowering plants such as Arabidopsis.

Originally discovered in Drosophila, PRC2 was identified as a crucial regulator of developmental genes, functioning through the alteration of chromatin structure to suppress specific gene expressions.

The initial belief that PRC2 primarily managed developmental gene control was reconsidered upon discovering its activity in single-cell organisms, where development does not occur.

Exploring PRC2’s Evolutionary Journey

The first clues to PRC2’s original function emerged from studies in red algae, showing PRC2’s methylation impact on transposons, the so-called jumping genes. This led Frederic Berger and his team at the Gregor Mendel Institute of Molecular Plant Biology, along with international collaborators from institutions like Freie Universität Berlin, University of Cambridge, and others, to investigate PRC2’s actions across various eukaryotes.

Through evolutionary development, PRC2 transitioned from suppressing transposons to inhibiting protein-coding genes.

Diverse Eukaryotic Studies of PRC2

The team delved into the genomes of three distinct eukaryotic lineages – plants, SAR, and opisthokonts (to which humans and fungi belong) – to understand PRC2’s ancestral role.

In these eukaryotes, transposons, which are capable of self-excising and reinserting in new DNA locations, pose a threat to genomic stability, necessitating their suppression. In mutated diatoms, bryophytes, and red algae, deactivating PRC2 led to a loss of transposon silencing.

Research Conclusions and Their Significance

The research demonstrates PRC2’s role in repressing transposons across these diverse lineages, suggesting this as an early evolutionary function. “This discovery of PRC2’s initial role as a genome protector against transposon invasion represents a significant paradigm shift,” states Frederic Berger, the study’s lead author.

Over time, however, PRC2’s role evolved from transposon suppression to the repression of protein-coding genes, as initially described. In terrestrial plants, PRC2 still targets what the researchers call “fossil TEs” for gene silencing in their vicinity.

“In more recently evolved flowering plants like Arabidopsis, remnants of TEs continue to attract PRC2, leading to the silencing of nearby genes,” explains Tetsuya Hisanaga, the study’s primary author. “Our hypothesis is that in Arabidopsis, some TEs have adapted to play a role in modulating protein-coding genes.”

Reference: “The Polycomb repressive complex 2 deposits H3K27me3 and represses transposable elements in a broad range of eukaryotes” by Tetsuya Hisanaga, Facundo Romani, and others, published on 21 September 2023 in Current Biology.
DOI: 10.1016/j.cub.2023.08.073

Frequently Asked Questions (FAQs) about PRC2 gene regulation

What is the Polycomb Repressive Complex 2 (PRC2)?

PRC2 is a protein complex originally identified as a key regulator of developmental genes. It functions by modifying chromatin structure, thus suppressing the expression of specific genes. Recent research has revealed a more ancestral role of PRC2 in protecting the genome against transposon invasions.

How has the understanding of PRC2’s role evolved?

Initially, PRC2 was understood to primarily control developmental genes. However, new research indicates its ancestral function was to defend the genome against transposon invasions, a role that has evolved over time. In contemporary biology, PRC2 is more involved in silencing protein-coding genes, especially in flowering plants.

What are the implications of the new findings on PRC2?

These new findings suggest that the primary function of PRC2 in ancestral eukaryotes was to suppress transposable elements, a role that has since evolved. This represents a profound paradigm shift in the understanding of gene regulation and the evolutionary history of genome protection mechanisms.

What was the methodology of the recent PRC2 study?

The study involved examining the genomes of various eukaryotic lineages, including plants, SAR, and opisthokonts. Researchers from several international institutions, including the Gregor Mendel Institute, conducted the research, focusing on PRC2’s impact on transposons and its evolutionary transition to gene silencing.

What are transposons, and why are they significant in this study?

Transposons, often called “jumping genes,” are mobile genetic elements that can move around within the genome. They pose a potential threat to genome stability, and the ancestral role of PRC2 was to suppress these transposons, ensuring genomic integrity. This study highlights the evolution of PRC2 from a transposon suppressor to a regulator of gene expression.

More about PRC2 gene regulation

  • Original Research Article – The full research article titled “The Polycomb repressive complex 2 deposits H3K27me3 and represses transposable elements in a broad range of eukaryotes,” published in Current Biology.
  • Gregor Mendel Institute – The official website of the Gregor Mendel Institute, where Frederic Berger and his research group conducted a significant part of the study.
  • Freie Universität Berlin – The official website of Freie Universität Berlin, one of the collaborating institutions in the research.
  • University of Cambridge – The official website of the University of Cambridge, another collaborating institution in the study.
  • National Institute of Genetics (Japan) – The official website of the National Institute of Genetics in Japan, contributing to the international collaboration.
  • Monash University – The official website of Monash University, also involved in the research project.

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