Evolutionarily young, gene-silencing piRNA: innovation in gene regulation or control of selfish genetic elements?
Authors: Peiwei Chen; Alexei Aravin
Affiliation: California Institute of Technology
Keywords: d. evolution of gene expression; s. siRNA/RNAi
Every genome is colonized by transposons, a class of selfish genetic elements that can mobilize and replicate themselves within the host genome, causing DNA damage and genome instability. To cope with this, animals employ a small RNA-guided genome defense mechanism to silence transposons. Particularly, the piRNA pathway is responsible for the repression of transposons in animal germline. Though piRNAs have been reported to regulate targets other than transposons, the range of these non-transposon piRNA targets in different species remains poorly explored. Previously, we profiled the piRNA repertoire in the male germline of Drosophila melanogaster and found abundant piRNAs from a locus on the Y chromosome that target and silence a protein-coding gene on the X chromosome, pirate. Pirate is an evolutionary young gene that encodes a putative deSUMOylase. Intriguingly, we found that in another Drosophila species, D. mauritiana, pirate is potentially repressed by another small RNA pathway, endogenous siRNA pathway, suggesting that two distinct small RNA-based silencing strategies were independently invented in recent evolution to regulate pirate. I will discuss our ongoing efforts in exploring whether pirate acts as a selfish genetic element and how different classes of small RNAs evolve to suppress pirate in the male germline.