The additional PRC2 subunit and Sin3 histone deacetylase complex are required for the normal distribution of H3K27me3 occupancy and transcriptional silencing in Magnaporthe oryzae

Abstract

Development in higher organisms requires proper gene silencing, partially achieved through trimethylation of lysine 27 on histone H3 (H3K27me3). However, how the normal distribution of this modification is established and maintained and how it affects gene expression remains unclear, especially in fungi. Polycomb repressive complex 2 (PRC2) catalyses H3K27me3 to assemble transcriptionally repressed facultative heterochromatin and is crucial in animals, plants, and fungi.Here, we report on the critical role of an additional PRC2 subunit in the normal distribution of H3K27me3 occupancy and the stable maintenance of gene repression in the rice fungal pathogen Magnaporthe oryzae. P55, identified as an additional PRC2 subunit, is physically associated with core subunits of PRC2 and is required for a complete level of H3K27me3 modification.Loss of P55 caused severe global defects in the normal distribution of H3K27me3 and transcriptional reprogramming on the H3K27me3-occupied genes. Furthermore, we found that the Sin3 histone deacetylase complex was required to sustain H3K27me3 occupancy and stably maintain gene repression by directly interacting with P55.Our results revealed a novel mechanism by which P55 and Sin3 participate in the normal distribution of facultative heterochromatic modifications and the stable maintenance of gene repression in eukaryotes.

Transcriptional Regulation of Autophagy-Related Genes by Sin3 Negatively Modulates Autophagy in Magnaporthe oryzae

“…In M. oryzae , autophagy is required for the degradation of the conidial components during appressorium formation ( 3 , 29 ). In our previous study, Sin3 was found to function primarily as a globally transcriptional repressor in M. oryzae ( 40 ). By analyzing the transcriptome sequencing (RNA-seq) data, we noted that expression levels of extensive autophagy-related genes ( ATGs ) were significantly upregulated in the Δ sin3 strain compared with those in the wild-type (WT) strain, which included ATG1 , ATG3 , ATG4 , ATG8 , ATG9 , ATG11 , ATG12 , ATG13 , ATG14 , ATG15 , ATG16 , ATG17 , ATG23 , ATG24 , ATG27 , ATG26 , and ATG29 (see Fig.…”

“…One layer is regulating the transcriptional expression of target genes at the transcriptional level and the other is regulating the acetylation of the target protein at the posttranslational level ( 41 ). In our recent study, the global level of acetylation of histone H4 lysine 16 (H4K16ac), which has been reported to be involved in the regulation of autophagy ( 6 ), was increased in the Δ sin3 strain ( 40 ).…”

“…However, Ume6 was not conserved among fungal species ( 36 ). In M. oryzae , our recent data indicated that Sin3 is physically associated with histone deacetylase Hos2 and Rpd3 ( 40 ). Furthermore, we found that Hos2 also negatively regulates autophagy like Sin3 (see Fig.…”

“… M. oryzae strain B157 was used as the wild-type (WT) strain for obtaining transformants ( 47 ). The Δ sin3 , Δ sin3 -C, GFP-ATG8, and H2B-mCherry strains were described previously ( 40 , 48 , 49 ). To generate the construct of SIN3-FLAG , the coding sequence of SIN3 was cloned to pFGL822-pRP27-FLAG .…”

“…In our previous study, we found that Sin3-HDAC is required for the normal distribution of trimethylation of lysine 27 on histone H3 (H3K27me3) occupancy and transcriptional silencing in M. oryzae ( 40 ). In this study, we revealed that Sin3 acts as a transcriptional repressor of ATGs to negatively regulate autophagy formation in M. oryzae .…”