Maintenance of heterochromatin by RNA interference of tandem repeats

Tandem repeats are prone to epigenetic silencing regulated by RNA interference. This may be because siRNAs from tandem array transcripts are regenerated by RNA-dependent RNA polymerase (RdRP) and Dicer, but siRNAs from single-copy sequences are exhausted by sequential use of downstream primers by RdRP. This could account for the formation of heterochromatin from tandem repeats.