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bioRxiv · 10.64898/2026.06.12.731976

Chromatin Assembly Factor 1 is required for normal structure and function of facultative heterochromatin in Neurospora crassa

Lewis, Z. A.·Torres, E. V.·Yap, R. E.·Ferraro, A. R.·Link, C. D.·Pelham, J. F.
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Abstract

Polycomb Repressive Complex 2 (PRC2) is a conserved epigenetic regulator that represses gene expression through methylation of histone H3 lysine 27 (H3K27me3). In animals, plants, and some fungi, PRC2-directed facultative heterochromatin plays essential roles in development and cellular differentiation. Here, we show that the replication-dependent histone chaperone Chromatin Assembly Factor 1 (CAF-1) is required for proper structure and function of facultative heterochromatin in the model fungus Neurospora crassa. Loss of CAF-1 causes widespread transcriptional misregulation, particularly within PRC2-repressed regions, and leads to redistribution of H3K27me3, reduced ASH1-dependent H3K36 methylation, and accumulation of chromatin marks associated with active transcription. CAF-1 was not required for repressive histone methylation within constitutive heterochromatin. A double mutant lacking both CAF-1 and PRC2 components displayed a synergistic silencing defect, suggesting these complexes make distinct contributions to facultative heterochromatin. Together, our findings indicate that CAF-1 works in concert with PRC2 to silence transcription within N. crassa facultative heterochromatin domains.

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Lewis, Z. A., Torres, E. V., Yap, R. E., Ferraro, A. R., Link, C. D., Pelham, J. F.. 2026-06-16. Chromatin Assembly Factor 1 is required for normal structure and function of facultative heterochromatin in Neurospora crassa. https://doi.org/10.64898/2026.06.12.731976

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