Heterochromatin revisited

Abstract

The formation of heterochromatin, which requires methylation of histone H3 at lysine 9 and the subsequent recruitment of chromodomain proteins such as heterochromatin protein HP1, serves as a model for the role of histone modifications and chromatin assembly in epigenetic control of the genome. Recent studies in Schizosaccharomyces pombe indicate that heterochromatin serves as a dynamic platform to recruit and spread a myriad of regulatory proteins across extended domains to control various chromosomal processes, including transcription, chromosome segregation and long-range chromatin interactions.

Aging by epigenetics—A consequence of chromatin damage?

“…Chromatin can be broadly divided into two types, heterochromatin and euchromatin [4]. Euchromatin is decondensed during interphase, relatively transcriptionally active and replicates early in S-phase.…”

Untimely expression of gametogenic genes in vegetative cells causes uniparental disomy

“…The three S. pombe chromosomes contain discrete blocks of facultative heterochromatin as well as constitutive heterochromatin domains such as at centromeres and telomeres 3,4 . RNAi–dependent and –independent mechanisms control gene expression and direct heterochromatin assembly.…”

“…RNAi–dependent and –independent mechanisms control gene expression and direct heterochromatin assembly. Heterochromatin HP1 proteins bound to methylated histone H3 lysine-9 (H3K9me) recruit effectors involved in gene silencing and proper chromosome segregation 3 . Indeed, cells lacking Clr4/Suv39h, HP1 or RNAi machinery show lagging chromosomes resulting from defects in heterochromatin-dependent cohesin localization at centromeres 5–7 .…”

“…4a-c; Extended Data Fig. 5c and 6d), which is the site of kinetochore assembly 3,24 . This aberrant localization of Psc3 at the central core in vegetative cells requires Rec8, as Psc3 was not enriched at the central core in mmi1∆ rec8 ∆ cells (Fig.…”

L’hétérochromatine constitutive dans tous ses états

“…Dans leur ensemble, ces résultats illustrent la plasticité de l'organisation 3D et la multiplicité fonctionnelle des régions centromériques. Chez la levure S. pombe, l'hétérochromatine constitutive est considérée comme une plate-forme dynamique pour le recrutement et la propagation de nombreux régulateurs impliqués dans diverses voies de régulation (transcription, ségrégation des chromosomes, réplication) (pour revue, voir [29]). Il est tentant de spéculer que l'hétérochro-matine constitutive chez les eucaryotes supérieurs constitue aussi une plate-forme d'assemblage associée à de nombreuses fonctions au cours du cycle cellulaire et de la différenciation cellulaire normale et pathologique.…”