In eukaryotic genomes, heterochromatin regulates various chromosomal processes including suppression of transcription and illegitimate recombination as well as proper segregation of chromosomes during cell division. Recent studies using the fission yeast Schizosaccharomyces pombe model system have revealed a complex interplay among RNA polymerase II transcription, RNAi machinery, and factors involved in posttranslational modifications of histones that are critical for the assembly and maintenance of heterochromatin. Heterochromatin proteins targeted to specific sites in the genome can spread across extended chromosomal domains and mediate epigenetic genome control by providing a recruitment platform for various factors including chromatin-modifying activities. In this chapter, we discuss mechanisms of heterochromatin assembly in fission yeast and highlight emerging evidence suggesting the involvement of heterochromatin factors in the suppression of noncoding RNAs across the genome.
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