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Strategies for Tracking Anastasis, A Cell Survival Phenomenon that Reverses Apoptosis
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Strategies for Tracking Anastasis, A Cell Survival Phenomenon that Reverses Apoptosis

Published on: February 16, 2015

Nuclear relocalization of the pre-mRNA splicing factor PSF during apoptosis involves hyperphosphorylation, masking of

Y Shav-Tal1, M Cohen, S Lapter

  • 1Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot, Israel.

Molecular Biology of the Cell
|August 22, 2001
PubMed

Insights

Nuclear organization of pre-mRNA splicing factor PSF changes during apoptosis. PSF remains intact but undergoes hyperphosphorylation, altering its interactions and potentially its function.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Spatial nuclear organization of regulatory proteins correlates with their function.
  • Pre-mRNA splicing factor PSF (Poly(A) signal binding protein nuclear factor) is crucial for gene expression.
  • PSF typically appears as discrete nuclear foci, which are lost during apoptosis.

Purpose of the Study:

  • To investigate the fate and nuclear organization of PSF during apoptosis.
  • To determine if PSF is degraded or modified during apoptosis.
  • To explore potential functional changes of PSF in apoptotic cells.

Main Methods:

  • Immunofluorescence microscopy using B92 mAb to visualize PSF.
  • Analysis of protein integrity and phosphorylation status via gel electrophoresis.
  • Expression of recombinant Green Fluorescent Protein (GFP)-tagged PSF.
  • Co-immunoprecipitation to identify PSF interacting partners.

Main Results:

  • PSF remains intact during apoptosis, contrary to expectations of degradation.
  • PSF undergoes N-terminal hyperphosphorylation on serine and threonine residues.
  • Differential phosphorylation patterns observed in mitosis, apoptosis, and G1/S phase arrest.
  • Apoptosis induces masking of PSF antigenic epitopes and reorganization into globular nuclear structures.
  • PSF dissociates from PTB and binds new partners like U1--70K and SR proteins.

Conclusions:

  • PSF is not degraded during apoptosis but undergoes significant post-translational modification (hyperphosphorylation).
  • These modifications lead to altered nuclear localization and protein interactions, suggesting a shift in PSF function during apoptosis.
  • The findings challenge the assumption that loss of nuclear foci equates to protein degradation and highlight dynamic protein reorganization in cell death pathways.

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