Topic
Heterochromatin
About: Heterochromatin is a research topic. Over the lifetime, 6782 publications have been published within this topic receiving 340476 citations. The topic is also known as: GO:0000792.
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TL;DR: The hypothesis that silencing in yeast results from heterochromatin formation is fortified and it is argued that the silencing proteins participate in this formation.
Abstract: Two classes of sequences in the yeast Saccharomyces cerevisiae are subject to transcriptional silencing: the silent mating-type cassettes and telomeres. In this report we demonstrate that the silencing of these regions is strictly associated with acetylation of the epsilon-amino groups of lysines in the amino-terminal domains of three of the four core histones. Both the silent mating-type cassettes and the Y domains of telomeres are packaged in nucleosomes in vivo that are hypoacetylated relative to those packaging active genes. This difference in acetylation is eliminated by genetic inactivation of silencing: The silent cassettes from sir2, sir3, or sir4 cells show the same level of acetylation as other active genes. The correspondence of silencing and hypoacetylation of the mating-type cassettes is observed even for an allele lacking a promoter, indicating that silencing per se, rather than the absence of transcription, is correlated with hypoacetylation. Finally, overexpression of Sir2p, a protein required for transcriptional silencing in yeast, yields substantial histone deacetylation in vivo. These studies fortify the hypothesis that silencing in yeast results from heterochromatin formation and argue that the silencing proteins participate in this formation.
850 citations
TL;DR: It is shown that < or =25% of DSBs require ATM signaling for repair, and this percentage correlates with increased chromatin but not damage complexity, which suggests that the importance of ATM signalling for DSB repair increases as the heterochromatic component of a genome expands.
845 citations
TL;DR: It is shown that the SIR3 and SIR4 proteins interact with specific silencing domains of the H3 and H4 N-termini in vitro, which proposes a model for heterochromatin-mediated transcriptional silencing in yeast, which may serve as a paradigm for other eukaryotic organisms as well.
809 citations
TL;DR: It is shown that transcriptionally inactive but not transcriptionally active genes associate with Ikaros-heterochromatin foci, which support a model of organization of the nucleus in which repressed genes are selectively recruited into centromeric domains.
789 citations
TL;DR: It is shown that distinct site-specific histone H3 methylation patterns define euchromatic and heterochromatic chromosomal domains within a 47-kilobase region of the mating-type locus in fission yeast.
Abstract: Eukaryotic genomes are organized into discrete structural and functional chromatin domains. Here, we show that distinct site-specific histone H3 methylation patterns define euchromatic and heterochromatic chromosomal domains within a 47-kilobase region of the mating-type locus in fission yeast. H3 methylated at lysine 9 (H3 Lys9), and its interacting Swi6 protein, are strictly localized to a 20-kilobase silent heterochromatic interval. In contrast, H3 methylated at lysine 4 (H3 Lys4) is specific to the surrounding euchromatic regions. Two inverted repeats flanking the silent interval serve as boundary elements to mark the borders between heterochromatin and euchromatin. Deletions of these boundary elements lead to spreading of H3 Lys9 methylation and Swi6 into neighboring sequences. Furthermore, the H3 Lys9 methylation and corresponding heterochromatin-associated complexes prevent H3 Lys4 methylation in the silent domain.
760 citations