Weak binding affinity of human 4EHP for mRNA cap analogs
- Joanna Zuberek1,4,
- Dorota Kubacka1,4,
- Agnieszka Jablonowska2,
- Jacek Jemielity1,
- Janusz Stepinski1,
- Nahum Sonenberg3, and
- Edward Darzynkiewicz1
- 1Department of Biophysics, Institute of Experimental Physics, Warsaw University, 02-089 Warsaw, Poland
- 2Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
- 3Department of Biochemistry and McGill Cancer Center, McGill University, Montreal, Quebec, H3G 1Y6, Canada
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↵4 These authors contributed equally to this work.
Abstract
Ribosome recruitment to the majority of eukaryotic mRNAs is facilitated by the interaction of the cap binding protein, eIF4E, with the mRNA 5′ cap structure. eIF4E stimulates translation through its interaction with a scaffolding protein, eIF4G, which helps to recruit the ribosome. Metazoans also contain a homolog of eIF4E, termed 4EHP, which binds the cap structure, but not eIF4G, and thus cannot stimulate translation, but it instead inhibits the translation of only one known, and possibly subset mRNAs. To understand why 4EHP does not inhibit general translation, we studied the binding affinity of 4EHP for cap analogs using two methods: fluorescence titration and stopped-flow measurements. We show that 4EHP binds cap analogs m7GpppG and m7GTP with 30 and 100 lower affinity than eIF4E. Thus, 4EHP cannot compete with eIF4E for binding to the cap structure of most mRNAs.
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Footnotes
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Reprint requests: Edward Darzynkiewicz, Department of Biophysics, Institute of Experimental Physics, Warsaw University, Zwirki i Wigury 93, 02-089 Warsaw, Poland; e-mail: edek{at}biogeo.uw.edu.pl; fax: +48 22 55 40771.
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Article published online ahead of print. Article and publication date are at http://www.rnajournal.org/cgi/doi/10.1261/rna.453107.
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- Received December 30, 2006.
- Accepted February 6, 2007.
- Copyright © 2007 RNA Society
