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The CCR4-NOT complex releases PABP from silenced miRNA targets in the absence of deadenylation

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Zekri,  L
Department Biochemistry, Max Planck Institute for Developmental Biology, Max Planck Society;

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Izaurralde,  E       
Department Biochemistry, Max Planck Institute for Developmental Biology, Max Planck Society;

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Citation

Zekri, L., & Izaurralde, E. (2013). The CCR4-NOT complex releases PABP from silenced miRNA targets in the absence of deadenylation. Poster presented at 8th Annual Meeting of the RNA Society (RNA 2013), Davos, Switzerland.


Cite as: https://hdl.handle.net/21.11116/0000-000B-4164-B
Abstract
GW182 family proteins interact with Argonaute proteins and are required for the translational repression,
deadenylation and decay of miRNA targets. To elicit these effects, GW182 proteins interact with PABP and the CCR4-
NOT deadenylase complex. Although the mechanism of miRNA target deadenylation is relatively well understood,
how GW182 proteins repress translation is not known. Here, we demonstrate that GW182 proteins decrease the
association of PABP with silenced targets in the absence of deadenylation. We further show that the dissociation of
PABP contributes approximately 2-fold to repression, indicating that additional repressive mechanisms are used by
miRISCs to achieve maximal target silencing. Remarkably, PABP dissociation requires the interaction of GW182
proteins with the CCR4-NOT complex but not with PABP. Accordingly, NOT1, POP2 and CCR4 cause dissociation
of PABP from bound mRNAs in the absence of deadenylation. Our findings indicate that the recruitment of the CCR4-
NOT complex to miRNA targets by GW182 proteins releases PABP from the mRNA poly(A) tail, thereby facilitating
translational repression and deadenylation. To gain further insight into the mechanism of PABP release by the CCR4-
NOT complex, we are currently investigating which subunit(s) of the CCR4-NOT complex contacts directly PABP
and is responsible for PABP release. Given the central role of the CCR4-NOT complex in post-transcriptional mRNA
regulation, we anticipate that this novel activity of the complex will contribute to the translational repression of a large
variety of different mRNAs.