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The human insulin receptor mRNA contains a functional internal ribosome entry segment

Spriggs, Keith A., Cobbold, Laura C., Ridley, Simon H., Coldwell, Mark J., Bottley, Andrew, Bushell, Martin, Willis, Anne E. and Siddle, Kenneth (2009) The human insulin receptor mRNA contains a functional internal ribosome entry segment Nucleic Acids Research, 37, (17), pp. 5881-5893. (doi:10.1093/nar/gkp623). (PMID:19654240).

Record type: Article

Abstract

Regulation of mRNA translation is an important mechanism determining the level of expression of proteins in eukaryotic cells. Translation is most commonly initiated by cap-dependent scanning, but many eukaryotic mRNAs contain internal ribosome entry segments (IRESs), providing an alternative means of initiation capable of independent regulation. Here, we show by using dicistronic luciferase reporter vectors that the 5'-UTR of the mRNA encoding human insulin receptor (hIR) contains a functional IRES. RNAi-mediated knockdown showed that the protein PTB was required for maximum IRES activity. Electrophoretic mobility shift assays confirmed that PTB1, PTB2 and nPTB, but not unr or PTB4, bound to hIR mRNA, and deletion mapping implicated a CCU motif 448 nt upstream of the initiator AUG in PTB binding. The IR-IRES was functional in a number of cell lines, and most active in cells of neuronal origin, as assessed by luciferase reporter assays. The IRES was more active in confluent than sub-confluent cells, but activity did not change during differentiation of 3T3-L1 fibroblasts to adipocytes. IRES activity was stimulated by insulin in sub-confluent cells. The IRES may function to maintain expression of IR protein in tissues such as the brain where mRNA translation by cap-dependent scanning is less effective.

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e-pub ahead of print date: 4 August 2009
Published date: September 2009
Organisations: Molecular and Cellular

Identifiers

Local EPrints ID: 204175
URI: http://eprints.soton.ac.uk/id/eprint/204175
ISSN: 0305-1048
PURE UUID: 07af092a-c42e-46b4-be71-6c51815ead94
ORCID for Mark J. Coldwell: ORCID iD orcid.org/0000-0002-6243-3886

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Date deposited: 24 Nov 2011 11:56
Last modified: 18 Jul 2017 11:06

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Contributors

Author: Keith A. Spriggs
Author: Laura C. Cobbold
Author: Simon H. Ridley
Author: Andrew Bottley
Author: Martin Bushell
Author: Anne E. Willis
Author: Kenneth Siddle

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