Chromatin Assembly Factor 1 is Required for Normal Gene Repression and Facultative Heterochromatin Formation in Neurospora crassa [RNA-seq]
Formation of facultative heterochromatin by Polycomb Repressive Complex 2 (PRC2) is a well conserved epigenetic mechanism that functions to control transcriptional dynamics across eukaryotes. PRC2 catalyzes histone H3 lysine 27 tri-methylation (H3K27me3), a histone post-translational modification that helps maintain stable gene repression. Gene repression by PRC2 is important for organismal development and defects in PRC2 function are associated with human ailments, such as Weaver syndrome and various cancers. In this study, we reveal the replication-dependent histone chaperone, Chromatin Assembly Factor 1 (CAF-1), is required for normal facultative heterochromatin formation in model fungus N. crassa. CAF-1 deficiency results in widespread misregulation of gene expression, particularly within facultative heterochromatin domains, which is accompanied by a rearrangement of H3K27me3 patterns. Regional losses of H3K27me3 are associated with reduced levels of ASH-1 catalyzed H3K36 methylation, and gains of histone modifications associated with active transcription. Furthermore, analysis of a double mutant deficient for both CAF-1 and PRC2 activity revealed that these complexes play distinct roles in maintaining gene repression and facultative heterochromatin. Collectively, these results shed light on CAF-1's role in maintaining a repressive chromatin environment. Overall design: RNA-seq performed on mycelial tissue after overnight growth in WT and mutant strains