Heterochromatin revisited

Heterochromatin was once considered the less-interesting part of the genome, the junk that had to be dealt with by being silenced. Recent studies in fission yeast indicate that heterochromatin has a role in various chromosomal processes, including transcription, chromosome segregation and long-range chromatin interactions. 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.