Wheat germ poly(A) binding protein enhances the binding affinity of eukaryotic initiation factor 4F and (iso)4F for cap analogues

Biochemistry. 1998 Feb 17;37(7):1910-6. doi: 10.1021/bi9724570.


Most eukaryotic mRNAs contain a 5' cap (m7GppX) and a 3' poly(A) tail to increase synergistically the translational efficiency. Recently, the poly(A) binding protein (PABP) and cap-binding protein, eIF-4F, were found to interact [Le et al. (1997) J. Biol. Chem. 272, 16247-16255; Tarun and Sachs (1996) EMBO J. 15, 7168-7177]. These data suggest that PABP may exert its effect on translational efficiency either by increasing the formation of initiation factor-mRNA complex or by enhancing ribosome recycling. To investigate the functional consequences of these interactions, the fluorescent cap analogue, ant-m7GTP, which is an environmentally sensitive fluorescent probe [Ren and Goss (1996) Nucleic Acids Res. 24, 3629-3634] was used to investigate the cap-binding affinity. Our data show that the binding of eIF-(iso)4F or eIF-4F to cap analogue enhanced their binding affinity toward PABP approximately 40-fold. Similarly, the eIF-4F/PABP or eIF-(iso)4F/PABP complexes show a 40-fold enhancement of cap analogue binding as compared to eIF-4F or eIF-(iso)4F alone. At least part of the enhancement of the translational initiation by PABP can be accounted for by direct changes in cap-binding affinity. The interactions of these components also suggest a mechanism whereby the poly(A) tail is brought into close proximity with m7G cap. This effect was examined by fluorescence energy transfer, and it was determined that the PABP/eIF-4F complex could bind both poly(A) and 5' cap simultaneously.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Binding Sites / drug effects
  • Binding Sites / genetics
  • Eukaryotic Initiation Factor-4F
  • Fluorescence Polarization
  • Peptide Chain Initiation, Translational / drug effects
  • Peptide Initiation Factors / metabolism*
  • Plant Proteins / physiology*
  • Poly A / metabolism*
  • Poly(A)-Binding Proteins
  • RNA Cap Analogs / metabolism*
  • RNA-Binding Proteins / physiology*
  • Spectrometry, Fluorescence
  • Triticum


  • Eukaryotic Initiation Factor-4F
  • Peptide Initiation Factors
  • Plant Proteins
  • Poly(A)-Binding Proteins
  • RNA Cap Analogs
  • RNA-Binding Proteins
  • Poly A