Real-time visualization of ZBP1 association with beta-actin mRNA during transcription and localization

Curr Biol. 2003 Feb 4;13(3):199-207. doi: 10.1016/s0960-9822(03)00044-7.


Background: mRNA localization in somatic cells is an important mechanism for gene expression regulation. In fibroblasts, the protein ZBP1 associates with the sequence that localizes beta-actin mRNA to the leading edge of fibroblasts, augmenting motility. beta-actin mRNA localizes in a cytoskeleton-dependent manner, depending on intact actin and myosin ATP-hydrolysis, and is largely bound to the actin cytoskeleton. The ZBP1 protein contains four KH RNA binding domains and a classic RBD RNA binding domain. It also contains a putative nuclear import and export sequence, suggesting a nuclear phase in this protein's function.

Results: Using high-speed imaging, we show here the targeting of this RNA binding protein to beta-actin pre-mRNA transcripts in the nuclei of living cells and measure the residence time of the RNA-protein complex before it leaves the transcription site. Then, the RNA-protein particle is exported to the cytoplasm, where it localizes at velocities of 0.6 microm/s by using actin filaments and/or microtubules. This RNA-ZBP1 complex is required for cytoplasmic localization in fibroblasts; mislocalizing the protein also mislocalizes the RNA, and expressing the protein in a ZBP1-deficient cell line induces beta-actin mRNA localization.

Conclusions: This work demonstrates that the RNA-protein association, essential for cytoplasmic localization, begins as soon as the RNA is transcribed. The ZBP1 then forms a ribonucleoprotein particle and moves in a myosin-dependent fashion by using the cytoskeleton for directional transport.

Publication types

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

MeSH terms

  • Actins / genetics*
  • Actins / metabolism
  • Active Transport, Cell Nucleus / physiology
  • Animals
  • Antibiotics, Antineoplastic / metabolism
  • Avian Proteins
  • Cell Line
  • Cell Nucleus / metabolism
  • Chick Embryo
  • Cytoplasm / metabolism
  • Cytoskeleton / metabolism
  • Cytoskeleton / ultrastructure
  • Fatty Acids, Unsaturated / metabolism
  • Myosins / metabolism
  • RNA, Messenger / metabolism*
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Transcription, Genetic*


  • Actins
  • Antibiotics, Antineoplastic
  • Avian Proteins
  • Fatty Acids, Unsaturated
  • RNA, Messenger
  • RNA-Binding Proteins
  • Recombinant Fusion Proteins
  • ZBP1 protein, Gallus gallus
  • Myosins
  • leptomycin B