Heterochromatin and the Control of Gene Silencing in Plants

Glimpses of evolution: heterochromatic histone H3K9 methyltransferases left its marks behind

“…Promotors which are silenced through H3K9 methylation should thus not be termed ''heterochromatized''. Wellknown properties of constitutive heterochromatin are condensation throughout interphase, high proportion of repetitious sequences, late S-phase replication, sparse transcription, suppression of recombination, spreading ability which results in PEV, sequence-unspecific selfinteraction, underreplication in polyploid nuclei, a regular spacing of nucleosomes, histone hypoacetylation, histone H3K4 hypomethylation, DNA hypermethylation and H3K9 hypermethylation (for review see e.g., Reuter et al 2005;Huisinga et al 2006). Not all of these properties are detectable in all organisms, but in most cytological analyzed eukaryotic species, defined heterochromatic blocks exist, often visible, side-by-side to active and silenced euchromatic regions.…”