Identification of a novel, tunable interface in the S.pombe HP1 protein, Swi6, that underpins epigenetic inheritance.
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ABSTRACT:
PROVIDER: PRJNA1043730 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR26908400_1.fastq.gz | Fastqsanger.gz | |||
| SRR26908400_2.fastq.gz | Fastqsanger.gz | |||
| SRR26908401_1.fastq.gz | Fastqsanger.gz | |||
| SRR26908401_2.fastq.gz | Fastqsanger.gz | |||
| SRR26908402_1.fastq.gz | Fastqsanger.gz |
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Project description:HP1 proteins bind dynamically to H3K9 methylation and are essential for establishing and maintaining transcriptionally silent epigenetic states, known as heterochromatin. HP1 proteins can dimerize, forming a binding interface that interacts with and recruits diverse chromatin-associated factors. HP1 proteins rapidly evolve through sequence changes and gene duplications, but the extent of variation required to achieve functional specialization is unknown. To investigate how changes in amino acid sequence impact epigenetic inheritance, we performed a targeted mutagenesis screen of the dimerization and protein interaction domain of the S.pombe HP1 homolog Swi6. We discovered that substitutions mapping to an auxiliary motif in Swi6 outside the dimerization interface can lead to complete functional divergence. Specifically, we identified point mutations at a single amino acid residue that resulted in either persistent gain or loss of function in epigenetic inheritance without affecting heterochromatin establishment. These substitutions increase Swi6 chromatin occupancy in vivo and alter Swi6-protein interactions that selectively affect H3K9me inheritance. Based on our findings, we propose that relatively minor changes in Swi6 amino acid composition can lead to profound changes in epigenetic inheritance, underscoring the remarkable plasticity associated with HP1 proteins and their ability to evolve new functions.
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Project description:HP1 proteins bind dynamically to H3K9 methylation and are essential for establishing and maintaining transcriptionally silent epigenetic states, known as heterochromatin. HP1 proteins can dimerize, forming a binding interface that interacts with and recruits diverse chromatin-associated factors. HP1 proteins rapidly evolve through sequence changes and gene duplications, but the extent of variation required to achieve functional specialization is unknown. To investigate how changes in amino acid sequence impact epigenetic inheritance, we performed a targeted mutagenesis screen of the dimerization and protein interaction domain of the S.pombe HP1 homolog Swi6. We discovered that substitutions mapping to an auxiliary motif in Swi6 outside the dimerization interface can lead to complete functional divergence. Specifically, we identified point mutations at a single amino acid residue that resulted in either persistent gain or loss of function in epigenetic inheritance without affecting heterochromatin establishment. These substitutions increase Swi6 chromatin occupancy in vivo and alter Swi6-protein interactions that selectively affect H3K9me inheritance. Based on our findings, we propose that relatively minor changes in Swi6 amino acid composition can lead to profound changes in epigenetic inheritance, underscoring the remarkable plasticity associated with HP1 proteins and their ability to evolve new functions.
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Project description:H3K9 methylation (H3K9me) marks transcriptionally silent genomic regions called heterochromatin. A conserved class of HP1 proteins are critically required to establish and maintain heterochromatin. HP1 proteins bind to H3K9me, recruit factors that promote heterochromatin formation, and oligomerize to form phase-separated condensates. We do not understand how HP1 protein binding to heterochromatin establishes and maintains transcriptional silencing. Here, we demonstrate that the S.pombe HP1 homolog, Swi6, can be completely bypassed to establish silencing at ectopic and endogenous loci when an H3K4 methyltransferase, Set1 and an H3K14 acetyltransferase, Mst2 are deleted. Deleting Set1 and Mst2 enhances Clr4 enzymatic activity, leading to higher H3K9me levels and increased spreading. In contrast, Swi6 and its capacity to oligomerize were indispensable during epigenetic maintenance. Our results demonstrate the role of HP1 proteins in regulating histone modification crosstalk during establishment and identifies a genetically separable function in maintaining epigenetic memory.
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Project description:HP1 proteins bind dynamically to H3K9 methylation and are essential for establishing and maintaining transcriptionally silent epigenetic states, known as heterochromatin. HP1 proteins can dimerize, forming a binding interface that interacts with and recruits diverse chromatin-associated factors. HP1 proteins rapidly evolve through sequence changes and gene duplications, but the extent of variation required to achieve functional specialization is unknown. To investigate how changes in amino acid sequence impact epigenetic inheritance, we performed a targeted mutagenesis screen of the dimerization and protein interaction domain of the S.pombe HP1 homolog Swi6. We discovered that substitutions mapping to an auxiliary motif in Swi6 outside the dimerization interface can lead to complete functional divergence. Specifically, we identified point mutations at a single amino acid residue that resulted in either persistent gain or loss of function in epigenetic inheritance without affecting heterochromatin establishment. These substitutions increase Swi6 chromatin occupancy in vivo and alter Swi6-protein interactions that selectively affect H3K9me inheritance. Based on our findings, we propose that relatively minor changes in Swi6 amino acid composition can lead to profound changes in epigenetic inheritance, underscoring the remarkable plasticity associated with HP1 proteins and their ability to evolve new functions.
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Project description:Proteins of the conserved HP1 family are elementary components of heterochromatin and are generally assumed to play a central role in creating a rigid heterochromatic network that is densely packed and inaccessible to the transcription machinery. In this study we demonstrate that the fission yeast HP1 protein Swi6 exists as a single highly dynamic population and rapidly exchanges in cis and in trans between different heterochromatic regions. Binding to methylated H3K9 or to heterochromatic RNA decelerates Swi6 mobility. We further show that Swi6 is largely dispensable to maintain heterochromatin domains. In contrast, our results disclose an unexpected role of Swi6 in demarcating constitutive heterochromatin from neighboring euchromatin. Our results are consistent with a stochastic model of heterochromatin and imply that heterochromatin is permissive for transcription throughout the cell cycle. Rather than promoting maintenance and spreading of heterochromatin, Swi6 appears to limit these processes to ensure that heterochromatin is appropriately confined.
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