RNA Elimination Machinery Targeting Meiotic mRNAs Promotes Facultative Heterochromatin Formation

Making Heterochromatin Heterochromatin is a particularly compact DNA-protein assembly that can repress gene expression. Constitutive heterochromatin is found, for example, at centromeres and the subtelomeric regions. Working with Schizosaccharomyces pombe , Zofall et al. (p. 96 , published online 1 December) examined the heterochromatin islands often found near meiotic genes, which are maintained in a silenced state during vegetative growth. Heterochromatin formation at these loci did not generally involve the RNA interference machinery, as is observed at centromeres, but did require transcription. The exosome, an RNA-degrading machine, was involved in the formation of the heterochromatin islands, which could be remodeled in response to sexual differentiation.