Heterochromatin-dependent transcription of satellite DNAs in the Drosophila melanogaster female germline

Large blocks of tandemly repeated DNAs—satellite DNAs (satDNAs)—play
important roles in heterochromatin formation and chromosome segregation.
We know little about how satDNAs are regulated, however their
misregulation is associated with genomic instability and human diseases.
We use the Drosophila melanogaster germline as a model to study the
regulation of satDNA transcription and chromatin. Here we show that
complex satDNAs (>100-bp repeat units) are transcribed into long
noncoding RNAs and processed into piRNAs (PIWI interacting RNAs). This
satDNA piRNA production depends on the Rhino-Deadlock-Cutoff complex and
the transcription factor Moonshiner—a previously-described non-canonical
pathway that licenses heterochromatin-dependent transcription of
dual-strand piRNA clusters. We show that this pathway is important for
establishing heterochromatin at satDNAs. Therefore, satDNAs are regulated
by piRNAs originating from their own genomic loci.  This novel
mechanism of satDNA regulation provides insight into the role of piRNA
pathways in heterochromatin formation and genome stability.