G-tract RNA removes Polycomb repressive complex 2 from genes

Area of Science:

• Molecular Biology
• Epigenetics
• Cancer Biology

Background:

• Polycomb repressive complex 2 (PRC2) is crucial for gene repression but can be aberrantly recruited in cancer.
• Understanding PRC2 removal mechanisms is key for reversing detrimental gene silencing.

Purpose of the Study:

• To investigate how PRC2 is removed from genes.
• To identify mechanisms for targeted reversal of aberrant PRC2 recruitment.

Main Methods:

• Studied PRC2 binding to G-tract RNA and G-quadruplex structures in nascent pre-mRNA.
• Observed PRC2 transfer from chromatin to pre-mRNA during gene activation in human and mouse cells.
• Targeted G-tract RNA to the CDKN2A gene in malignant rhabdoid tumor cells.

Main Results:

• PRC2 preferentially binds G tracts in pre-mRNA, especially G-quadruplex structures.
• G-quadruplex RNA can evict the PRC2 catalytic core from nucleosomes.
• Chromatin-associated G-tract RNA mediates PRC2 removal upon gene activation, leading to H3K27me3 depletion.
• Targeting G-tract RNA to CDKN2A reactivated the gene and induced senescence in cancer cells.

Conclusions:

• Pre-mRNA, via G-tract RNA, plays a role in evicting PRC2 during gene activation.
• This mechanism provides a means for selective PRC2 removal from specific genes.
• G-tract RNA represents a potential therapeutic target for reactivating silenced tumor suppressor genes.