Target-specific requirements for enhancers of decapping in miRNA-mediated gene silencing.
microRNAs (miRNAs) silence gene expression by suppressing protein production and/or by promoting mRNA decay. To elucidate how silencing is accomplished, we screened an RNA interference library for suppressors of miRNA-mediated regulation in Drosophila melanogaster cells. In addition to proteins known to be required for miRNA biogenesis and function (i.e., Drosha, Pasha, Dicer-1, AGO1, and GW182), the screen identified the decapping activator Ge-1 as being required for silencing by miRNAs. Depleting Ge-1 alone and/or in combination with other decapping activators (e.g., DCP1, EDC3, HPat, or Me31B) suppresses silencing of several miRNA targets, indicating that miRNAs elicit mRNA decapping. A comparison of gene expression profiles in cells depleted of AGO1 or of individual decapping activators shows that approximately 15% of AGO1-targets are also regulated by Ge-1, DCP1, and HPat, whereas 5% are dependent on EDC3 and LSm1-7. These percentages are underestimated because decapping activators are partially redundant. Furthermore, in the absence of active translation, some miRNA targets are stabilized, whereas others continue to be degraded in a miRNA-dependent manner. These findings suggest that miRNAs mediate post-transcriptional gene silencing by more than one mechanism.
Eulalio
Ana
A
Max Planck Institute for Developmental Biology, D-72076 Tübingen, Germany.
Rehwinkel
Jan
J
Stricker
Mona
M
Huntzinger
Eric
E
Yang
Schu-Fee
SF
Doerks
Tobias
T
Dorner
Silke
S
Bork
Peer
P
Boutros
Michael
M
Izaurralde
Elisa
E
D000818:Animals; D060565:Argonaute Proteins; D002460:Cell Line; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000378:metabolism; D039642:Eukaryotic Initiation Factors; D017344:Genes, Insect; D017930:Genes, Reporter; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D014176:Protein Biosynthesis; D012315:RNA Caps / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
C489654:AGO1 protein, Drosophila; D060565:Argonaute Proteins; D029721:Drosophila Proteins; D039642:Eukaryotic Initiation Factors; D035683:MicroRNAs; D012315:RNA Caps; D012333:RNA, Messenger