Project description:We report the application of ChIP-sequencing technology for high-throughput profiling of histone modifications in budding yeast. By obtaining over four billion bases of sequence from chromatin immunoprecipitated DNA, we generated genome-wide maps of Set1 and H3K4me3 in yeast cells. We find that Set1 and H3 lysine 4 trimethylation locate primarily in open reading frame of genes. In addition, we focus on the distribution of Set1 and H3K4me3 in histone gene clusters and found strong similar binding of Set1 and H3K4me3 on all histone genes.
Project description:Prp45 is a budding yeast NineTeen-Complex associated factor, which plays a role in pre-mRNA splicing. Because its human ortholog, SNW1/SKIP, is known to functionally and physically interact with factors involved in transcription elongation and chromatin modifications, it was suggested to be one of the coupling factors which functionally connect splicing and transcription. To determine whether yeast Prp45 has this function as well we tested the genetic interactions between prp45(1-169) allele and deletions of histone modifiers and transcription elongation regulators. RNA-seq analysis was performed to address the changes in transcription and/or splicing in strains deleted in set1, a histone methyltransferase responsible for H3K4 methylation, and the corresponding prp45(1-169) set1 double mutant. Total RNA was isolated by combining phenol-chlorophorm extraction with MasterPure Yeast RNA Purification Kit (Epicentre). Ribodepletion, library preparation and sequencing were performed by BGI Genomics.
Project description:H3K4me3 is catalyzed by the Set1/MLL family of methyltransferases, whose function in catalyzing H3K4me3 is unique. Impaired function of Set1/MLL family members can lead to many abnormalities, such as bone and nerve defects, leukemia, and even death. Although the Set1 family plays an important regulatory role in various biological processes, it is still unclear how the Set1 protein itself is regulated and how protein levels are maintained. Due to the numerous homologues, complex composition, and high molecular weight of Set1 in higher organisms, especially humans, related research is greatly limited. In brewing yeast, Set1 is the only methyltransferase that catalyzes H3K4me3 and is highly conserved between species. Therefore, yeast is an ideal model for studying the functions and mechanisms of the Set1 family. In addition, Set1 protein plays an important role in regulating gene transcription, promoting telomere silencing, and maintaining cell lifespan. The Set1 family also plays an important regulatory role in the occurrence and development of various cancers.
Project description: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.
Project description: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.
Project description:Histone modifications affect DNA-templated processes ranging from transcription to genomic replication. In this study, we examine the cell cycle dynamics of the trimethylated form of histone H3 lysine 4 (H3K4me3), a mark of active chromatin that is viewed as “long-lived” [1], and that is involved in memory during cell state inheritance in metazoans [2]. We synchronized yeast using two different protocols, then followed H3K4me3 patterns as yeast passed through subsequent cell cycles. While most H3K4me3 patterns were conserved from one generation to the next, we found that methylation patterns induced by alpha factor or high temperature were erased within one cell cycle, during S phase. Early-replicating regions were erased before late-replicating regions, implicating replication in H3K4me3 loss. However, incomplete H3K4me3 erasure occurred at the majority of loci even when replication was prevented, suggesting that most erasure results from an active process. Indeed, deletion of the demethylase Jhd2 slowed erasure at most loci. Together, these results indicate overlapping roles for passive dilution and active enzymatic demethylation in erasing ancestral histone methylation states in yeast. References: [1] Ng HH, Robert F, Young RA, Struhl K (2003) Targeted recruitment of Set1 histone methylase by elongating Pol II provides a localized mark and memory of recent transcriptional activity. Mol Cell 11: 709-719. [2] Ringrose L, Paro R (2004) Epigenetic regulation of cellular memory by the Polycomb and Trithorax group proteins. Annu Rev Genet 38: 413-443.
Project description:RNAi, a gene-silencing pathway triggered by double-stranded RNA, is conserved in diverse eukaryotic species but has been lost in the model budding yeast, Saccharomyces cerevisiae. We report that RNAi is present in other budding-yeast species, including Saccharomyces castellii and Candida albicans. These species use noncanonical Dicer proteins to generate siRNAs, which mostly correspond to transposable elements and Y´ subtelomeric repeats. In S. castellii, RNAi mutants are viable but have excess Y´ mRNA levels. In S. cerevisiae, introducing Dicer and Argonaute of S. castellii restores RNAi, and the reconstituted pathway silences endogenous retrotransposons. These results identify a novel class of Dicer proteins, bring the tool of RNAi to the study of budding yeasts, and bring the tools of budding yeast to the study of RNAi.