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Abstract
Chromatin, a complex of DNA and proteins, plays a vital role in regulating gene expression. This work focuses specifically on facultative heterochromatin, characterized by the tri-methylation of histone H3 at lysine 27 (H3K27me3), which serves as a molecular marker of transcriptionally silenced chromatin. This modification is deposited by the multi-subunit complex known as Polycomb Repressive Complex 2 (PRC2). To investigate the mechanisms governing the assembly and maintenance of facultative heterochromatin, we utilized the model fungus Neurospora crassa. Our findings reveal that a complex containing Histone Deacetylase-1 (HDA-1) in N. crassa plays a regulatory role in PRC2 activity. Notably, deletion of hda-1 results in a global redistribution of H3K27 methylation from its typical PRC2-targeted domains to regions of constitutive heterochromatin, alongside observed genome instability linked to other histone modifications. Furthermore, we developed a reporter system that enables the separation of sequence-specific establishment of H3K27me3 from its maintenance across multiple generations. This research harnesses the unique attributes of Neurospora to enhance our understanding of the interactions between PRC2 and other factors in regulating the dynamics of facultative heterochromatin.