Argonaute Utilization for miRNA Silencing Is Determined by Phosphorylation-Dependent Recruitment of LIM-Domain-Containing Proteins

Publication date: 5 July 2017
Source:Cell Reports, Volume 20, Issue 1
Author(s): Katherine S. Bridge, Kunal M. Shah, Yigen Li, Daniel E. Foxler, Sybil C.K. Wong, Duncan C. Miller, Kathryn M. Davidson, John G. Foster, Ruth Rose, Michael R. Hodgkinson, Paulo S. Ribeiro, A. Aziz Aboobaker, Kenta Yashiro, Xiaozhong Wang, Paul R. Graves, Michael J. Plevin, Dimitris Lagos, Tyson V. Sharp
As core components of the microRNA-induced silencing complex (miRISC), Argonaute (AGO) proteins interact with TNRC6 proteins, recruiting other effectors of translational repression/mRNA destabilization. Here, we show that LIMD1 coordinates the assembly of an AGO-TNRC6 containing miRISC complex by binding both proteins simultaneously at distinct interfaces. Phosphorylation of AGO2 at Ser 387 by Akt3 induces LIMD1 binding, which in turn enables AGO2 to interact with TNRC6A and downstream effector DDX6. Conservation of this serine in AGO1 and 4 indicates this mechanism may be a fundamental requirement for AGO function and miRISC assembly. Upon CRISPR-Cas9-mediated knockout of LIMD1, AGO2 miRNA-silencing function is lost and miRNA silencing becomes dependent on a complex formed by AGO3 and the LIMD1 family member WTIP. The switch to AGO3 utilization occurs due to the presence of a glutamic acid residue (E390) on the interaction interface, which allows AGO3 to bind to LIMD1, AJUBA, and WTIP irrespective of Akt signaling.

Graphical abstract

Teaser

Argonaute (AGO) proteins mediate post-transcriptional gene silencing through formation of the microRNA-induced silencing complex (miRISC). Bridge et al. identify LIM-domain-containing proteins as essential for miRISC formation through a phosphorylation-dependent mechanism. This is critical for post-transcriptional gene silencing and reveals that miRISC functionality is maintained by "AGO switching."


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