Article abstract
Nature Structural & Molecular Biology 16, 144 - 150 (2009)
Published online: 1 February 2009 | doi:10.1038/nsmb.1552
Biological basis for restriction of microRNA targets to the 3' untranslated region in mammalian mRNAs
Shuo Gu1, Lan Jin1, Feijie Zhang1, Peter Sarnow2 & Mark A Kay1
Abstract
MicroRNAs (miRNAs) interact with target sites located in the 3' untranslated regions (3' UTRs) of mRNAs to downregulate their expression when the appropriate miRNA is bound to target mRNA. To establish the functional importance of target-site localization in the 3' UTR, we modified the stop codon to extend the coding region of the transgene reporter through the miRNA target sequence. As a result, the miRNAs lost their ability to inhibit translation but retained their ability to function as small interfering RNAs in mammalian cells in culture and in vivo. The addition of rare but not optimal codons upstream of the extended opening reading frame (ORF) made the miRNA target site more accessible and restored miRNA-induced translational knockdown. Taken together, these results suggest that active translation impedes miRNA-programmed RISC association with target mRNAs and support a mechanistic explanation for the localization of most miRNA target sites in noncoding regions of mRNAs in mammals.
- The Center for Clinical Science Research, Room 2105, 269 Campus Drive, Stanford, California 94305-5164, USA.
- Department of Microbiology and Immunology, 300 Pasteur Drive, Room D309, Stanford University, Stanford, California 94305, USA.
Correspondence to: Mark A Kay1 e-mail: markay@stanford.edu
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