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Genome-wide RNAi Screening to Identify Host Factors That Modulate Oncolytic Virus Therapy
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Viral oncolysis that targets Raf-1 signaling control of nuclear transport

Laura Riolobos1, Noelia Valle, Eva Hernando

  • 1Centro de Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.

Journal of Virology
|November 27, 2009
PubMed

Insights

Raf-1 kinase phosphorylation of parvovirus capsid proteins is essential for their nuclear import and viral replication. This finding reveals a new target for oncolytic viral therapy in cancers with abnormal Raf signaling.

Area of Science:

  • Oncology
  • Virology
  • Molecular Biology

Background:

  • Raf protein kinase isoforms are crucial in human cancers, necessitating targeted inhibitors.
  • Parvoviruses exhibit oncotropism and a lytic cycle, making them candidates for experimental cancer therapy.

Purpose of the Study:

  • To investigate the mechanisms of parvovirus oncolysis, focusing on the interaction between parvovirus proteins and Raf-1 kinase.
  • To identify novel therapeutic targets for viral oncolysis in cancer treatment.

Main Methods:

  • Investigated phosphorylation of minute virus of mice (MVM) major structural protein (VP) trimers by Raf-1 kinase.
  • Assessed nuclear import of MVM VP trimers in digitonin-permeabilized human cells with and without Raf-1 activity.
  • Examined the effect of Raf-1 inhibition on MVM capsid assembly and viral maturation in infected cells.

Main Results:

  • Raf-1 kinase phosphorylates MVM VP trimers, a process critical for their nuclear translocation.
  • VP trimers from insect cells (lacking Raf-1) were not phosphorylated or imported into the nucleus, unlike those from mammalian cells.
  • Restoring Raf-1 activity in insect cells enabled VP trimer phosphorylation and nuclear import.
  • Raf-1 inhibition led to cytoplasmic retention of MVM capsid proteins, hindering nuclear assembly and virus maturation.
  • Higher Raf-1 activity in cancer cells correlated with increased VP phosphorylation and MVM permissiveness.

Conclusions:

  • Raf-1 kinase-mediated phosphorylation controls the nuclear import of MVM capsid assembly intermediates, representing a novel target for oncolytic viral therapy.
  • Minute virus of mice (MVM) could enhance therapies for human cancers characterized by dysregulated Raf signaling.

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