Leo1 and Set1-mediated H3K4me3 contribute to sterol homeostasis in yeast [ChIPseq]

Project Abstract : Trimethylation of histone H3 lysine 4 (H3K4me3) is predominantly associated with transcriptional start sites (TSSs) and is believed to facilitate transcription initiation. Furthermore, H3K4me3 plays a role in defining cell fate and specific cellular functions. Nevertheless, the precise function of H3K4me3 in transcription activation remains a topic of ongoing debate. The Polymerase-associated factor 1 complex (Paf1C), which is integral to various transcription-related cellular processes, consists of five highly conserved subunits: Paf1, Ctr9, Rtf1, Cdc73, and Leo1. While all subunits of Paf1C are indispensable for the maintenance of H3K4 methylation levels, it is noteworthy that strains lacking Leo1 exhibited unaltered levels of H3K4me3. To elucidate the role of H3K4me3, we conducted a transcriptome analysis coupled with ChIP-sequencing of H3K4me3 in cells lacking Leo1. Our research uncovers a distinctive role of Leo1 in yeast, whereby it plays a pivotal role in maintaining sterol homeostasis through the suppression of Upc2 expression. Importantly, this role stands apart from the functions of other Paf1C subunits. H3K4me3 is essential for promoting the expression of sterol uptake genes that are Upc2-dependent when Leo1 is absent. Additionally, Set1 contributes to sterol homeostasis by regulating iron metabolism and mitochondrial functions rather than directly suppressing Upc2 expression. Therefore, our findings reveal a novel role for Leo1 in sterol homeostasis and highlight the importance of H3K4me3 in promoting transcription of response genes required for sterol uptake. Sample number (1-5): We performed anti-H3K4me3 ChIPseq with WT(1,2), Δleo1(3,4), and Δset1(5) strains. Experiments in WT and Δleo1 strains were performed in duplicates, and anti-H3K4me3 ChIPseq with Δset1 strain(5) was performed to reveal the background signal of the experiment.