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Isolation of Translating Ribosomes Containing Peptidyl-tRNAs for Functional and Structural Analyses
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Polypyrimidine tract-binding protein inhibits translation of bip mRNA

Y K Kim1, B Hahm, S K Jang

  • 1NRL, Department of Life Science, Division of Molecular and Life Sciences, Pohang University of Science and Technology, San31, Pohang, Hyoja-Dong, 790-784, Korea.

Journal of Molecular Biology
|November 18, 2000
PubMed

Insights

Polypyrimidine tract-binding protein (PTB) binds to the human Bip mRNA internal ribosomal entry site (IRES). PTB can inhibit or enhance Bip translation, revealing its complex role in IRES-mediated translation initiation.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Genetics

Background:

  • Translation initiation is a critical regulatory step in gene expression.
  • Internal ribosomal entry site (IRES) elements mediate cap-independent translation initiation.
  • The polypyrimidine tract-binding protein (PTB) is known to modulate IRES-dependent translation for some viruses.

Purpose of the Study:

  • To investigate the role of PTB in the IRES-dependent translation of human Bip mRNA.
  • To identify the binding site of PTB on the Bip 5' non-translated region.
  • To determine how PTB affects Bip translation initiation.

Main Methods:

  • RNA-protein binding assays to determine PTB interaction with Bip mRNA.
  • In vitro translation assays using rabbit reticulocyte lysate.
  • Cell-based assays involving PTB overexpression and depletion in Cos-7 cells.

Main Results:

  • PTB specifically binds to the central region (nucleotides 50-117) of the human Bip 5' non-translated region.
  • Exogenous PTB inhibits Bip IRES-dependent translation in vitro and in vivo.
  • Depletion of endogenous PTB or addition of a PTB-interacting RNA enhances Bip IRES activity.

Conclusions:

  • PTB directly interacts with the human Bip mRNA IRES.
  • PTB exhibits a dual role, inhibiting Bip IRES-dependent translation under certain conditions.
  • These findings highlight the context-dependent regulatory function of PTB in mRNA translation.

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