Messenger RNA is a functional component of a chromatin insulator complex

Chromatin insulators are DNA protein complexes situated throughout the genome capable of demarcating independent transcriptional domains. Previous studies point to an important role for RNA in gypsy chromatin insulator function in Drosophila; however, the identity of these putative insulator-associated RNAs is not currently known. Here we utilize RNA-immunoprecipitation and high throughput sequencing (RIP-seq) to isolate RNAs stably associated with gypsy insulator complexes. Strikingly, these RNAs correspond to specific sense-strand, spliced and polyadenylated mRNAs, including two insulator protein transcripts. In order to assess the functional significance of these associated mRNAs independent of their coding function, we expressed untranslatable versions of these transcripts in developing flies and observed both alteration of insulator complex nuclear localization as well as improvement of enhancer-blocking activity. Together, these data suggest a novel, noncoding mechanism by which certain mRNAs contribute to chromatin insulator function.