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Silent chromatin at the middle and ends: lessons from yeasts.

Bühler M, Gasser SM - EMBO J. (2009)

Bottom Line: However, the ultimate behaviour of silent chromatin and the pathways that assemble it seem strikingly similar among Saccharomyces cerevisiae (S. cerevisiae), Schizosaccharomyces pombe (S. pombe) and other eukaryotes.Thus, studies in both yeasts have been instrumental in dissecting the mechanisms that establish and maintain silent chromatin in eukaryotes, contributing substantially to our understanding of epigenetic processes.In this review, we discuss current models for the generation of heterochromatic domains at centromeres and telomeres in the two yeast species.

View Article: PubMed Central - PubMed

Affiliation: Epigenetics Focal Area, Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.

ABSTRACT
Eukaryotic centromeres and telomeres are specialized chromosomal regions that share one common characteristic: their underlying DNA sequences are assembled into heritably repressed chromatin. Silent chromatin in budding and fission yeast is composed of fundamentally divergent proteins tat assemble very different chromatin structures. However, the ultimate behaviour of silent chromatin and the pathways that assemble it seem strikingly similar among Saccharomyces cerevisiae (S. cerevisiae), Schizosaccharomyces pombe (S. pombe) and other eukaryotes. Thus, studies in both yeasts have been instrumental in dissecting the mechanisms that establish and maintain silent chromatin in eukaryotes, contributing substantially to our understanding of epigenetic processes. In this review, we discuss current models for the generation of heterochromatic domains at centromeres and telomeres in the two yeast species.

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Variegated expression of a gene on packaging into a heterochromatic structure. (A) Cells expressing the wild-type ADE2 gene from its endogenous, euchromatic locus produce colonies that are white, (B) whereas those lacking the ADE2 gene appear red. (C) Juxtaposition of ADE2 to heterochromatin results in its silencing without changing the underlying coding sequence. Although inherited, the packaging state of ADE2 (euchromatic versus heterochromatic) can switch at a low frequency. This results in a variegating phenotype in a clonal population of cells. An example of a telomeric position effect (TPE) (Gottschling et al, 1990) in S. cerevisiae is shown here.
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f1: Variegated expression of a gene on packaging into a heterochromatic structure. (A) Cells expressing the wild-type ADE2 gene from its endogenous, euchromatic locus produce colonies that are white, (B) whereas those lacking the ADE2 gene appear red. (C) Juxtaposition of ADE2 to heterochromatin results in its silencing without changing the underlying coding sequence. Although inherited, the packaging state of ADE2 (euchromatic versus heterochromatic) can switch at a low frequency. This results in a variegating phenotype in a clonal population of cells. An example of a telomeric position effect (TPE) (Gottschling et al, 1990) in S. cerevisiae is shown here.

Mentions: Whether the telomeric functions of capping and end-replication behave epigenetically is unclear, yet telomere-associated gene silencing is one of the classic examples of semi-stable, yet heritable, transcriptional repression (Figure 1) (Gottschling et al, 1990). Both native subtelomeric genes and reporters integrated into telomere proximal zones succumb to transcriptional silencing through chromatin-mediated mechanisms. Despite the fact that the subtelomeric repression of transcription in budding and fission yeast share many heterochromatin-like features, the molecular mechanisms of repression differ significantly, as explained below.


Silent chromatin at the middle and ends: lessons from yeasts.

Bühler M, Gasser SM - EMBO J. (2009)

Variegated expression of a gene on packaging into a heterochromatic structure. (A) Cells expressing the wild-type ADE2 gene from its endogenous, euchromatic locus produce colonies that are white, (B) whereas those lacking the ADE2 gene appear red. (C) Juxtaposition of ADE2 to heterochromatin results in its silencing without changing the underlying coding sequence. Although inherited, the packaging state of ADE2 (euchromatic versus heterochromatic) can switch at a low frequency. This results in a variegating phenotype in a clonal population of cells. An example of a telomeric position effect (TPE) (Gottschling et al, 1990) in S. cerevisiae is shown here.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2722250&req=5

f1: Variegated expression of a gene on packaging into a heterochromatic structure. (A) Cells expressing the wild-type ADE2 gene from its endogenous, euchromatic locus produce colonies that are white, (B) whereas those lacking the ADE2 gene appear red. (C) Juxtaposition of ADE2 to heterochromatin results in its silencing without changing the underlying coding sequence. Although inherited, the packaging state of ADE2 (euchromatic versus heterochromatic) can switch at a low frequency. This results in a variegating phenotype in a clonal population of cells. An example of a telomeric position effect (TPE) (Gottschling et al, 1990) in S. cerevisiae is shown here.
Mentions: Whether the telomeric functions of capping and end-replication behave epigenetically is unclear, yet telomere-associated gene silencing is one of the classic examples of semi-stable, yet heritable, transcriptional repression (Figure 1) (Gottschling et al, 1990). Both native subtelomeric genes and reporters integrated into telomere proximal zones succumb to transcriptional silencing through chromatin-mediated mechanisms. Despite the fact that the subtelomeric repression of transcription in budding and fission yeast share many heterochromatin-like features, the molecular mechanisms of repression differ significantly, as explained below.

Bottom Line: However, the ultimate behaviour of silent chromatin and the pathways that assemble it seem strikingly similar among Saccharomyces cerevisiae (S. cerevisiae), Schizosaccharomyces pombe (S. pombe) and other eukaryotes.Thus, studies in both yeasts have been instrumental in dissecting the mechanisms that establish and maintain silent chromatin in eukaryotes, contributing substantially to our understanding of epigenetic processes.In this review, we discuss current models for the generation of heterochromatic domains at centromeres and telomeres in the two yeast species.

View Article: PubMed Central - PubMed

Affiliation: Epigenetics Focal Area, Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.

ABSTRACT
Eukaryotic centromeres and telomeres are specialized chromosomal regions that share one common characteristic: their underlying DNA sequences are assembled into heritably repressed chromatin. Silent chromatin in budding and fission yeast is composed of fundamentally divergent proteins tat assemble very different chromatin structures. However, the ultimate behaviour of silent chromatin and the pathways that assemble it seem strikingly similar among Saccharomyces cerevisiae (S. cerevisiae), Schizosaccharomyces pombe (S. pombe) and other eukaryotes. Thus, studies in both yeasts have been instrumental in dissecting the mechanisms that establish and maintain silent chromatin in eukaryotes, contributing substantially to our understanding of epigenetic processes. In this review, we discuss current models for the generation of heterochromatic domains at centromeres and telomeres in the two yeast species.

Show MeSH