Archer, Stuart K.Shirokikh, Nikolay E.Hallwirth, Claus V.Beilharz, Traude H.Preiss, Thomas2015-09-072015-09-071547-6286http://hdl.handle.net/1885/15230The mRNA closed-loop, formed through interactions between the cap structure, poly(A) tail, eIF4E, eIF4G and PAB, features centrally in models of eukaryotic translation initiation, although direct support for its existence in vivo is not well established. Here, we investigated the closed-loop using a combination of mRNP isolation from rapidly cross-linked cells and high-throughput qPCR. Using the interaction between these factors and the opposing ends of mRNAs as a proxy for the closed-loop, we provide evidence that it is prevalent for eIF4E/4G-bound but unexpectedly sparse for PAB1-bound mRNAs, suggesting it primarily occurs during a distinct phase of polysome assembly. We observed mRNA-specific variation in the extent of closed-loop formation, consistent with a role for polysome topology in the control of gene expression.Funding was provided by the Australian Research Council under grant number DP1300101928. TP was supported by an NHMRC Senior Research Fellowship. NES was supported by a Go8 European Fellowship.© Stuart K Archer, Nikolay E Shirokikh, Claus V Hallwirth, Traude H Beilharz, and Thomas Preiss. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The moral rights of the named author(s) have been asserted.cap-poly(a) synergyeukaryotic translationmrna closed-looppolysomes, ribosomal recycling2015-03-3110.1080/15476286.2015.1017242