Model of post-transcriptional regulation of protein-coding genes by the Piwi/piRNA pathway.

<p>(A) piRNA cluster containing a protein-coding gene. (B) Hypothetical model of post-transcriptional gene regulation mediated by piRNA clusters, based on data of porcine piRNAs. piRNA clusters containing sequences of genes or pseudogenes in reverse orientation relative to the cluster directionality can presumably produce primary piRNAs complementary to spliced mRNA, which can direct the decay of such transcripts and produce secondary piRNAs within the ping-pong amplification loop.