Preprint identifies RTT109 as required for PRC2-repressed chromatin maintenance in Neurospora

A preprint deposited on bioRxiv on 14 May 2026 reports that RTT109 — a histone acetyltransferase best characterised in budding yeast for its role in acetylating histone H3 at lysine 56 (H3K56ac) to promote chromatin reassembly after DNA replication — is required for the normal maintenance of Polycomb Repressive Complex 2 (PRC2)-silenced chromatin in Neurospora crassa.

PRC2 catalyses trimethylation of histone H3 lysine 27 (H3K27me3), a conserved mark of transcriptional repression found in animals, plants, and some fungi. The researchers show that deletion of rtt109 in N. crassa disrupts the structure and function of H3K27me3-marked chromatin domains, implicating RTT109 in a maintenance pathway for epigenetic silencing that has not previously been described.

Unexpectedly, the requirement for RTT109 appears to be independent of its H3K56 acetylation activity, dissociating the two functions. The team also demonstrates that N. crassa RTT109 physically interacts with a homologue of the yeast co-factor VPS75, suggesting the relevant protein complex is conserved even where its downstream targets have diverged.

The findings add to a growing body of work on the cross-talk between chromatin assembly factors and Polycomb silencing machinery. Because PRC2 and H3K27me3 are central to gene regulation in multicellular organisms, understanding the full complement of factors required for their maintenance has broad relevance to developmental biology and epigenetics research. This is a preprint and has not yet undergone peer review.