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Department of Biochemistry and Molecular Pharmacology

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MicroRNAs; RNA-Induced Silencing Complex


Biochemistry, Biophysics, and Structural Biology | Genetics and Genomics | Life Sciences | Medicine and Health Sciences


BACKGROUND: MicroRNA (miRNA) are diverse in sequence and have a single known sequence bias: they tend to start with uridine (U).

RESULTS: Our analyses of fly, worm and mouse miRNA sequence data reveal that the 5'-U is recognized after miRNA production. Only one of the two strands can be assembled into Argonaute protein from a single miRNA/miRNA* molecule: in fly embryo lysate, a 5'-U promotes miRNA loading while decreasing the loading of the miRNA*.

CONCLUSION: We suggest that recognition of the 5'-U enhances Argonaute loading by a mechanism distinct from its contribution to weakening base pairing at the 5'-end of the prospective miRNA and, as recently proposed in Arabidopsis and in humans, that it improves miRNA precision by excluding incorrectly processed molecules bearing other 5'-nt.

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© 2011 Seitz et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

DOI of Published Version



Silence. 2011 Jun 7;2:4. Link to article on publisher's site

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