Functional diversification of Dicer-like proteins and small RNAs required for genome sculpting.
In eukaryotes, small RNAs (sRNAs) have key roles in development, gene expression regulation, and genome integrity maintenance. In ciliates, such as Paramecium, sRNAs form the heart of an epigenetic system that has evolved from core eukaryotic gene silencing components to selectively target DNA for deletion. In Paramecium, somatic genome development from the germline genome accurately eliminates the bulk of typically gene-interrupting, noncoding DNA. We have discovered an sRNA class (internal eliminated sequence [IES] sRNAs [iesRNAs]), arising later during Paramecium development, which originates from and precisely delineates germline DNA (IESs) and complements the initial sRNAs ("scan" RNAs [scnRNAs]) in targeting DNA for elimination. We show that whole-genome duplications have facilitated successive differentiations of Paramecium Dicer-like proteins, leading to cooperation between Dcl2 and Dcl3 to produce scnRNAs and to the production of iesRNAs by Dcl5. These innovations highlight the ability of sRNA systems to acquire capabilities, including those in genome development and integrity.
Institute of Cell Biology, University of Bern, Baltzerstrasse 4, Bern 3012, Switzerland.
Pamela Y
PY
Sandoval
Institute of Cell Biology, University of Bern, Baltzerstrasse 4, Bern 3012, Switzerland.
Estienne C
EC
Swart
Institute of Cell Biology, University of Bern, Baltzerstrasse 4, Bern 3012, Switzerland.
Miroslav
M
Arambasic
Institute of Cell Biology, University of Bern, Baltzerstrasse 4, Bern 3012, Switzerland. Electronic address: mariusz.nowacki@izb.unibe.ch.
Mariusz
M
Nowacki
D016054:DNA, Protozoan / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing; D018503:Genome, Protozoan; D016805:Paramecium tetraurelia / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D010802:Phylogeny; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D016053:RNA, Protozoan / Q000235:genetics* / Q000378:metabolism; D058727:RNA, Small Untranslated / Q000235:genetics* / Q000378:metabolism; D043244:Ribonuclease III / Q000235:genetics* / Q000378:metabolism
D016054:DNA, Protozoan; D015800:Protozoan Proteins; D016053:RNA, Protozoan; D058727:RNA, Small Untranslated; D043244:Ribonuclease III