Drosophila Scm self-assembles into PcG bodies to recruit PRC2.1 to target genes during Polycomb silencing initiation.

Scm self-assembles into PcG bodies to recruit PRC2.1, enabling rapid formation of H3K27me3 domains during Polycomb silencing in Drosophila.

• Why it matters: Understanding how large, repressive H3K27me3 domains are formed and maintained is crucial for insights into gene regulation and development, yet these mechanisms are not fully known.
• What they did: The study used Drosophila nurse cells to investigate silencing initiation, revealing that Scm polymerizes into PcG bodies independently of PRC1 and PRC2, then recruits PRC2 via a direct interaction involving the Scm-Zf-FCS and Pcl-Tudor domains.
• The result: This mechanism is essential for viability and Hox gene regulation, suggesting that controlling Scm polymerization could influence the size and placement of H3K27me3 domains, impacting gene silencing dynamics.