Piwi-like: PIWI domain. Domain found in proteins involved in RNA silencing. RNA silencing refers to a group of related gene-silencing mechanisms mediated by short RNA molecules, including siRNAs, miRNAs, and heterochromatin-related guide RNAs. The central component of the RNA-induced silencing complex (RISC) and related complexes is Argonaute. The PIWI domain is the C-terminal portion of Argonaute and consists of two subdomains, one of which provides the 5' anchoring of the guide RNA and the other, the catalytic site for slicing. This domain is also found in closely related proteins, including the Piwi subfamily, where it is believed to perform a crucial role in germline cells, via a similar mechanism.