RNAi-dependent and independent control of LINE1 accumulation and mobility in mouse embryonic stem cells.
In most mouse tissues, long-interspersed elements-1 (L1s) are silenced via methylation of their 5'-untranslated regions (5'-UTR). A gradual loss-of-methylation in pre-implantation embryos coincides with L1 retrotransposition in blastocysts, generating potentially harmful mutations. Here, we show that Dicer- and Ago2-dependent RNAi restricts L1 accumulation and retrotransposition in undifferentiated mouse embryonic stem cells (mESCs), derived from blastocysts. RNAi correlates with production of Dicer-dependent 22-nt small RNAs mapping to overlapping sense/antisense transcripts produced from the L1 5'-UTR. However, RNA-surveillance pathways simultaneously degrade these transcripts and, consequently, confound the anti-L1 RNAi response. In Dicer(-/-) mESC complementation experiments involving ectopic Dicer expression, L1 silencing was rescued in cells in which microRNAs remained strongly depleted. Furthermore, these cells proliferated and differentiated normally, unlike their non-complemented counterparts. These results shed new light on L1 biology, uncover defensive, in addition to regulatory roles for RNAi, and raise questions on the differentiation defects of Dicer(-/-) mESCs.
Swiss Federal Institute of Technology Zurich, Department of Biology, Chair of RNA biology, Zurich, Switzerland ; Institut Curie, CNRS UMR3215, Paris, France.
Constance
C
Ciaudo
Florence
F
Jay
Ikuhiro
I
Okamoto
Chong-Jian
CJ
Chen
Alexis
A
Sarazin
Nicolas
N
Servant
Emmanuel
E
Barillot
Edith
E
Heard
Olivier
O
Voinnet
D020121:5' Untranslated Regions; D000818:Animals; D060565:Argonaute Proteins / Q000235:genetics*; D002454:Cell Differentiation / Q000235:genetics; D049109:Cell Proliferation; D053487:DEAD-box RNA Helicases / Q000235:genetics* / Q000378:metabolism; D019175:DNA Methylation / Q000235:genetics; D053595:Embryonic Stem Cells / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics*; D051379:Mice; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D018626:Retroelements / Q000235:genetics; D043244:Ribonuclease III / Q000235:genetics* / Q000378:metabolism
D020121:5' Untranslated Regions; C526735:Ago2 protein, mouse; D060565:Argonaute Proteins; D018626:Retroelements; C509781:Dicer1 protein, mouse; D043244:Ribonuclease III; D053487:DEAD-box RNA Helicases