Regional control of histone H3 lysine 27 methylation in Neurospora

Area of Science:

• Epigenetics
• Fungal Biology
• Gene Regulation

Background:

• Histone H3 trimethylated at lysine 27 (H3K27me3) is a conserved epigenetic mark found across eukaryotes, except in yeasts.
• H3K27me3 plays a crucial role in transcriptional silencing and developmental processes.
• Its presence and function in filamentous fungi like Neurospora crassa remain largely unexplored.

Purpose of the Study:

• To investigate the presence, genomic distribution, and functional significance of H3K27me3 in Neurospora crassa.
• To identify the core components of the Polycomb Repressive Complex 2 (PRC2) responsible for H3K27me3 deposition in this species.
• To determine the impact of H3K27me3 loss on gene expression patterns.

Main Methods:

• Chromatin immunoprecipitation followed by sequencing (ChIP-seq) to map H3K27me3 genomic distribution.
• Comparative genomic analysis of H3K27me3-marked genes across related Neurospora species.
• Gene deletion and knockout studies to assess the role of PRC2 components.
• Transcriptional profiling using RNA sequencing to analyze gene expression changes.

Main Results:

• H3K27me3 marks 6.8% of the N. crassa genome, defining 223 domains and silencing 774 genes.
• H3K27me3-marked genes in N. crassa exhibit lower conservation and limited cross-species marking compared to other eukaryotes.
• The PRC2 components SET-7, EED, and SUZ12 are essential for H3K27me3, while NP55 is specifically required for subtelomeric marking.

Conclusions:

• H3K27me3 functions as a repressive epigenetic mark in N. crassa, primarily associated with transcriptionally silent and less conserved genes.
• The Neurospora PRC2 complex, with specific roles for its subunits, mediates H3K27me3 deposition.
• Loss of H3K27me3 leads to the upregulation of numerous genes, highlighting its regulatory role in fungal gene expression.