The let-7 target gene mouse lin-41 is a stem cell specific E3 ubiquitin ligase for the miRNA pathway protein Ago2.
The let-7 miRNA and its target gene Lin-28 interact in a regulatory circuit controlling pluripotency. We investigated an additional let-7 target, mLin41 (mouse homologue of lin-41), as a potential contributor to this circuit. We demonstrate the presence of mLin41 protein in several stem cell niches, including the embryonic ectoderm, epidermis and male germ line. mLin41 colocalized to cytoplasmic foci with P-body markers and the miRNA pathway proteins Ago2, Mov10 and Tnrc6b. In co-precipitation assays, mLin41 interacted with Dicer and the Argonaute proteins Ago1, Ago2 and Ago4. Moreover, we show that mLin41 acts as an E3 ubiquitin ligase in an auto-ubiquitylation assay and that mLin41 mediates ubiquitylation of Ago2 in vitro and in vivo. Overexpression and depletion of mLin41 led to inverse changes in the level of Ago2 protein, implicating mLin41 in the regulation of Ago2 turnover. mLin41 interfered with silencing of target mRNAs for let-7 and miR-124, at least in part by antagonizing Ago2. Furthermore, mLin41 cooperated with the pluripotency factor Lin-28 in suppressing let-7 activity, revealing a dual control mechanism regulating let-7 in stem cells.
Rybak
Agnieszka
A
Center for Anatomy, Institute of Cell Biology and Neurobiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Fuchs
Heiko
H
Hadian
Kamyar
K
Smirnova
Lena
L
Wulczyn
Ellery A
EA
Michel
Geert
G
Nitsch
Robert
R
Krappmann
Daniel
D
Wulczyn
F Gregory
FG
D000818:Animals; D060565:Argonaute Proteins; D018236:Carcinoma, Embryonal / Q000235:genetics; D002478:Cells, Cultured; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000235:genetics*; D011485:Protein Binding; D013094:Spermatozoa / Q000378:metabolism; D013234:Stem Cells / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D057149:Ubiquitinated Proteins / Q000378:metabolism
C526735:Ago2 protein, mouse; D060565:Argonaute Proteins; D015852:Eukaryotic Initiation Factor-2; C511366:LIN-41 protein, mouse; D035683:MicroRNAs; D014157:Transcription Factors; D057149:Ubiquitinated Proteins; C542687:mirnlet7 microRNA, mouse; D044767:Ubiquitin-Protein Ligases