Fig. 2
From: The biogenesis and biological function of PIWI-interacting RNA in cancer
Regulatory mechanisms and biological functions of piRNAs and piRNA/PIWI complexes. (A) TGS mainly occurs on PIWI proteins with low catalytic activity. The role of piRNAs in gene expression modification is similar to that of DNA methylation. (B) PTGS usually requires PIWI proteins to perform cleavage because it depends on target transcriptional fragments. Here, piRNAs play a role similar to that of miRNAs. (C) Both piRNAs and PAZ domains of PIWI proteins in the piRNA/PIWI complex can directly bind to some proteins and thus promote multiprotein interactions