Five eIF4E isoforms from Arabidopsis thaliana are characterized by distinct features of cap analogs binding.

Anna Kropiwnicka, Krzysztof Kuchta, Maciej Lukaszewicz, Joanna Kowalska, Jacek Jemielity, Krzysztof Ginalski, Edward Darzynkiewicz, Joanna Zuberek

Journal: Biochemical and biophysical research communications 2015;456(1):47-52

PMID: 25446076

Full Text on Elsevier Science View on PubMed

Abstract

The assembly of the ribosome on majority of eukaryotic mRNAs is initiated by the recruitment of eIF4E protein to the mRNA 5' end cap structure. Flowering plants use two eIF4E isoforms, named eIF4E and eIF(iso)4E, as canonical translation initiation factors and possess a homolog of mammalian 4EHP (or eIF4E-2) termed nCBP. Plants from Brassicaceae family additionally conserve a close paralog of eIF4E which in Arabidopsis thaliana has two copies named eIF4E1b and eIF4E1c. In order to assess the efficiency of plant non-canonical (eIF4E1b/1c and nCBP) and canonical (eIF4E and eIF(iso)4E) eIF4E proteins to bind mRNAs we utilized fluorescence titrations to determine accurate binding affinities of five A.thaliana eIF4E isoforms for a series of cap analogs. We found that eIF4E binds cap analogs from 4-fold to 10-fold stronger than eIF(iso)4E, while binding affinities of nCBP and eIF(iso)4E are comparable. Furthermore, eIF4E1c interacts similarly strongly with the cap as eIF4E, but eIF4E1b binds cap analogs ca. 2-fold weaker than eIF4E1c, regardless of the 95% sequence identity between these two proteins. The use of differentially chemically modified cap analogs in binding studies and a detailed analysis of the obtained homology models gave us insight into the molecular characteristic of varying cap-binding abilities of Arabidopsis eIF4E isoforms.

Address: College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences, University of Warsaw, Zwirki i Wigury 93, 02-089 Warsaw, Poland; Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Zwirki i Wigury 93, 02-089 Warsaw, Poland.; College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences, University of Warsaw, Zwirki i Wigury 93, 02-089 Warsaw, Poland; Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097 Warsaw, Poland.; Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Zwirki i Wigury 93, 02-089 Warsaw, Poland.; Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Zwirki i Wigury 93, 02-089 Warsaw, Poland; Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097 Warsaw, Poland.; Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097 Warsaw, Poland.; Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Zwirki i Wigury 93, 02-089 Warsaw, Poland. Electronic address: [email protected].

DOI: 10.1016/j.bbrc.2014.11.032

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MeSH Terms: Amino Acid Sequence, Arabidopsis, Arabidopsis Proteins, Eukaryotic Initiation Factor-4E, Gene Expression Profiling, Gene Expression Regulation, Plant, Guanosine Triphosphate, Molecular Sequence Data, Organothiophosphates, Protein Binding, Protein Isoforms, Protein Structure, Secondary, Protein Structure, Tertiary, Sequence Homology, Amino Acid, Spectrometry, Fluorescence, Thermodynamics