The Cutoff protein regulates piRNA cluster expression and piRNA production in the Drosophila germline

In a broad range of organisms, Piwi-interacting RNAs (piRNAs) have emerged as core components of a surveillance system that protects the genome by silencing transposable and repetitive elements. A vast proportion of piRNAs is produced from discrete genomic loci, termed piRNA clusters. The molecular mechanisms and the factors that govern the expression of these loci are largely unknown. We have preciously shown the Cutoff (Cuff), a protein with similarity to yeast Rai1, is a component of the piRNA pathway. In order to understand the function of the Cuff protein in piRNA production, we produced small RNA libraries from cn, bw (wt) and cuffwm25 mutant ovaties. The analysis of these libraries revealed that approximately 80% of the total piRNA population is depleted in the absence of a functional Cuff protein. We also determined that Cuff is mostly a nuclear protein and is enriched at the level of certain piRNA clusters. Our results point to a role for Cuff in the transcriptional regulation of piRNA generating loci and in the production of the proper piRNA complement during Drosophila oogenesis. piRNA profiling in ovaries from cn, bw and cuffwm25 mutant ovaries