Epigenetic maintenance of PRC2-repressed chromatin requires RTT109 but not H3K56 acetylation.

RTT109 is essential for maintaining PRC2-repressed chromatin in Neurospora crassa independently of H3K56 acetylation, with its catalytic activity being crucial.

• Why it matters: Understanding how epigenetic states are preserved during cell division is vital for insights into gene regulation and inheritance. The role of specific histone modifications in this process remains unclear, especially in fungi.
• What they did: Researchers identified RTT109 as a key regulator of PRC2-repressed domains, demonstrating that its catalytic activity, not NAF-2 or H3K56 acetylation, is necessary for proper chromatin structure and function, and that H3K27me3 can be propagated without sequence-specific PRC2 targeting.
• The result: The study reveals a replication-linked mechanism for epigenetic memory, positioning RTT109 as a critical factor in Polycomb-mediated chromatin inheritance and stability across multiple cell divisions.