Fig. 1
From: The emerging role of the piRNA/PIWI complex in respiratory tract diseases
The biosynthesis of PIWI-interacting RNAs (PiRNAs). In the nucleus, the uni-stranded piRNA cluster are transcribed into the primary piRNAs transcripts, which are transported to the cytoplasmic nuage. There, the primary piRNAs transcripts are spliced by Zuc and its co-factor (mino) to produce piRNA intermediates with 5ʹuracil. After binding to the PIWI protein, the 3ʹ end is modified by Zuc or Trimmer and its cofactor Papi, which is an exonuclease. Following methylation by Hen1, the mature piRNA-PIWI complex is generated