Fig. 2

Regulation mechanism of PIWI-piRNA complex in normal cells. In normal cells, PIWI proteins mainly bind to piRNA to form complexes that regulate gene expression at the transcriptional or post-transcriptional level. At the transcription level, the target gene transcription is regulated mainly by nuclear localization PIWI protein recruiting histones and DNA modification enzymes. At the post-transcriptional level, in addition to the epigenetic regulatory factors such as MTC, ubiquitination enzyme and phosphorylase recruited by PIWI proteins in the cytoplasm and regulated at the level of RNA and proteasome, the target gene mRNA can also be directly targeted and cleaved in a PIWI endonuclease-dependent manner, which is realized in the “Ping-pong” cycle pathway