PETISCO is a novel protein complex required for 21U RNA biogenesis and embryonic viability.

Piwi proteins are important for germ cell development in most animals. These proteins are guided to specific targets by small guide RNAs, referred to as piRNAs or 21U RNAs in In this organism, even though genetic screens have uncovered 21U RNA biogenesis factors, little is known about how these factors interact or what they do. Based on the previously identified 21U biogenesis factor PID-1 (piRNA-induced silencing-defective 1), we here define a novel protein complex, PETISCO (PID-3, ERH-2, TOFU-6, and IFE-3 small RNA complex), that is required for 21U RNA biogenesis.

Maternal piRNAs Are Essential for Germline Development following De Novo Establishment of Endo-siRNAs in Caenorhabditis elegans.

The Piwi-piRNA pathway represents a germline-specific transposon-defense system. C. elegans Piwi, prg-1, is a non-essential gene and triggers a secondary RNAi response that depends on mutator genes, endo-siRNAs (22G-RNAs), and the 22G-RNA-binding Argonaute protein HRDE-1.

PID-1 is a novel factor that operates during 21U-RNA biogenesis in Caenorhabditis elegans.

The Piwi-piRNA pathway represents a small RNA-based mechanism responsible for the recognition and silencing of invading DNA. Biogenesis of piRNAs (21U-RNAs) is poorly understood. In Caenorhabditis elegans, the piRNA-binding Argonaute protein PRG-1 is the only known player acting downstream from precursor transcription.

Is this mine? small RNAs help to decide.

Genomes are constantly challenged by invaders, so determining what belongs is crucial. Small RNAs silence alien DNA, but Conine et al. (2013), Seth et al.