Keeping the neighbours quiet: A lesson from C. elegans in using what you have to hand
Researchers from the Institute of Molecular Biology (IMB) in Mainz have uncovered a new evolutionary origin for the anti-parasitic genome defence system, piRNAs, in worms. In their research paper published in Genes and Development
, the group of Prof. René Ketting describe how the piRNA pathway in C.elegans
developed out of a more ancient, evolutionarily conserved protein system that is needed for correct gene expression.
While studying the piRNA system in the small nematode C. elegans
, the group discovered a new protein complex essential for their production, which they called PETISCO -tapas in Portuguese. This protein complex appears to have two distinct functions, flavours, that are determined by its interaction partners, PID-1 and TOST-1. PID-1, in evolutionary terms a relatively young protein, uses PETISCO to make piRNAs, while TOST-1, a genetically older protein, has a gene expression function. While TOST-1’s function still needs to be molecularly defined, it appears to be involved in producing small RNA molecules needed to join gene segments together to create a functional transcript. The results strongly suggest that this latter, essential PETISCO system has been coopted later during C. elegans
’ evolutionary history to produce piRNAs. Indeed, this new finding highlights how evolution can build on existing structures to derive novel effective parasite-control systems.
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