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Replication and active demethylation represent partially overlapping mechanisms for erasure of H3K4me3 in budding yeast

ABSTRACT: 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.

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE14565 | GEO | 2009/01/28

SECONDARY ACCESSION(S): PRJNA111569

REPOSITORIES: GEO

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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 â??long-livedâ?? [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. The overall design of the experiment consists of two cell cycle experiments, each consisting of the following subsets: gene expression, ChIP with anti-H3K4Me3 antibody, and ChIP input. The experiments are as follows: CCA - BY4741 bar1- cells synchronized by alpha factor arrest; CCTS - BY4741 cdc28(ts) cells synchronized by arrest at non-permissive temperature. The individual time courses are enumerated as follows: CCA gene expression (array title "Synchronized cells, xxx min, cell cycle CCA"), 18 arrays; CCA ChIP for anti-H3K4Me3 (array title "H3K4Me3 ChIP cell cycle CCA, xxx min"), 17 arrays, 1 replicate; CCA ChIP input (array title "ChIP Input cell cycle CCA, xxx min"), 18 arrays, 1 replicate; CCTS gene expression (appears in a different dataset as biological replicate "I"; array title "Synchronized cells, xxx min, biological replicate I"), 18 arrays; CCTS ChIP for anti-H3K4Me3 (array title "H3K4Me3 cell cycle CCTS, xxx min"), 2 technical replicates, 18 arrays per replicate; CCTS ChIP input (array title "ChIP Input cell cycle CCTS, xxx min"), 2 technical replicates, 18 arrays per replicate. Gene expression arrays were run against a reference of unsynchronized cells, ChIP-chip anti-H3K4Me3 samples were run against an IP (of the same epitope) of unsynchronized cells, and ChIP input samples were run against either a pool of all the time points in the time course (CCTS) or against sonicated DNA isolated from unsynchronized cells (CCA). Four additional experiments have been performed. They are referred to as series X in the title. Series 1: anti H3K4me3 CHIP time course of BY4741 bar1 delete cells (wt) synchronized with alpha factor and released in the cell cycle, 9 arrays, 1 replicate. Series 2: anti H3K4me3 CHIP time course of BY4741 bar1 jhd2 delete cells (jhd2 delete) synchronized with alpha factor and released in the cell cycle, 7 arrays, 1 replicate. Series 3: anti H3K4me3 CHIP time course of CYM36 cells (cdc7ts) synchronized with alpha factor and released in the cell cycle at the permissive 24C or at the restrictive 37C temperature, 22 arrays, 2 replicates. Series 4: anti H3K4me3 CHIP time course of BY4741 bar1 delete cells (wt) grown in galactose and synchronized with alpha factor and either released in the cell cycle in glucose media or alpha factor arrested and switched to glucose media, 6 arrays, 1 replicate.

Project description:Full title: Complex patterns of genome accessibility discriminate sites of PcG repression, H4K16 acetylation and replication initiation Histone modifications have been proposed to regulate gene expression in part by modulating DNA accessibility and higher-order chromatin structure. However, there is limited direct evidence to support structural differences between euchromatic and heterochromatic fibers in the nucleus. To ask how histone modifications relate to chromatin compaction, we measured DNA accessibility throughout the genome by combining M.SssI methylase footprinting with methylated DNA immunoprecipitation (MeDIP-footprint). In the Drosophila genome, we find that accessibility to DNA methylase is variable in a manner that relates to the differential distribution of active and repressive histone modifications. Active promoters are highly permissive to M.SssI activity, yet inactive chromosomal domains decorated with H3 lysine 27 trimethylation are least accessible providing in vivo evidence for Polycomb-mediated chromatin compaction. Conversely, DNA accessibility is increased at active chromosomal regions marked with H4 lysine 16 acetylation and at the dosage-compensated male X chromosome suggesting that Drosophila transcriptional dosage compensation is facilitated by more permissive chromatin structure. Interestingly early replicating chromosomal regions and sites of replication initiation show also higher accessibility linking temporal and spatial control of genome duplication to the structural organization of chromatin. In conclusion, using a novel protocol we generated a comprehensive view of DNA accessibility and uncover different levels of chromatin organization, which are delineated by distinct patterns of posttranslational histone modifications and replication. Keywords: cell type comparison, ChIP-chip, MeDIP-footprint, RNA-seq, ChIP-seq MeDIP-footprint and ChIP-chip: ChIP-chip was performed for H3K4me3, H3K36me2, H3K36me3, H3K27me3, and H3K9me2 in Kc cells. We measured DNA accessibility throughout the genome by combining M.SssI methylase footprinting with methylated DNA immunoprecipitation (MeDIP-footprint) in Kc and S2 cells. RNA-seq: cDNA from RNA from Drosophila Kc cells was sequenced using Illumina deep sequencing. Reads were mapped and the abundance of all transcripts was determined. ChIP-seq: PSC ChIP from Drosophila Kc cells was sequenced using Illumina deep sequencing in three lanes. Reads were mapped and the binding profile of PSC was determined.

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Replication and active demethylation represent partially overlapping mechanisms for erasure of H3K4me3 in budding yeast

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