Fig 5. Model describing generation of phased piRNAs from nxf2.

TART-A produces abundant antisense piRNAs derived from ping-pong amplification, including from the TART-A/nxf2 region of shared homology (blue box on red background). The PIWI protein Aubergine binds antisense ping-pong piRNAs, a subset of which share homology with nxf2. These piRNAs guide Aub to nxf2 and result in cleavage of the transcript between the 10th and 11th nucleotide of the guide piRNA. Transcript cleavage creates an nxf2 cleavage product that shares a 10-bp sense:antisense overlap with the guide piRNA (see S8 Fig). The nxf2 cleavage product can by subsequently processed by the Zucchini endonuclease, creating phased piRNAs starting from the site of Aub cleavage and proceeding to the 3′ end of the nxf2 transcript. piRNA, Piwi-interacting small RNA.