Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 109, Issue 4, Pages 1104-1109Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1113350109
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Funding
- Japan Ministry of Education, Culture, Sports, Science and Technology [22115510, 20112003]
- Uehara Memorial Foundation
- Senri Life Science Foundation
- Asahi Glass Foundation
- Grants-in-Aid for Scientific Research [22115510, 22115511, 20112003] Funding Source: KAKEN
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MicroRNA (miRNA) is a class of small noncoding RNA approximately 22 nt in length. Animal miRNA silences complementary mRNAs via translational inhibition, deadenylation, and mRNA degradation. However, the underlying molecular mechanisms remain unclear. A key question is whether these three outputs are independently induced by miRNA through distinct mechanisms or sequentially induced within a single molecular pathway. Here, we successfully dissected these intricate outputs of miRNA-mediated repression using zebrafish embryos as a model system. Our results indicate that translational inhibition and deadenylation are independent outputs mediated by distinct domains of TNRC6A, which is an effector protein in the miRNA pathway. Translational inhibition by TNRC6A is divided into two mechanisms: PAM2 motif-mediated interference of poly(A)-binding protein (PABP), and inhibition of 5' cap- and poly(A) tail-independent step(s) by a previously undescribed P-GL motif. Consistent with these observations, we show that, in zebrafish embryos, miRNA inhibits translation of the target mRNA in a deadenylation- and PABP-independent manner at early time points. These results indicate that miRNA exerts multiple posttranscriptional outputs via physically and functionally independent mechanisms and that direct translational inhibition is central to miRNA-mediated repression.
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