Traffic Jam activates the piRNA cluster locus and the Piwi pathway to ensure transposon silencing and fertility.

is the most prominent piRNA cluster locus expressed in ovarian follicle cells, and it is required for female fertility to silence transposons. To determine how is regulated, we used promoter-bashing reporter assays in OSS cells to uncover novel enhancer sequences within the first exons of . We confirmed the enhancer sequence relevance in vivo with new deletion mutants of these regions that compromised piRNA expression and lowered female fertility from activated transposons. Our proteomic analysis of proteins associated with these enhancer sequences discovered the transcription factor Traffic Jam (TJ). knockdowns in OSS cells caused a decrease in transcripts, piRNAs, and multiple Piwi pathway genes. A TJ ChIP-seq analysis from whole flies and OSS cells confirmed TJ binding exactly at the enhancer that was deleted in the new mutant as well as at multiple Piwi pathway gene enhancers. Interestingly, TJ also bound the Long Terminal Repeats of transposons that had decreased expression after knockdowns in OSS cells. Our study reveals the integral role TJ plays in the on-going arms race between selfish transposons and their suppression by the host Piwi pathway and the piRNA cluster locus.