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Analysis of Cell Cycle Position in Mammalian Cells
12:19

Analysis of Cell Cycle Position in Mammalian Cells

Published on: January 21, 2012

Inhibition of S-phase progression by adeno-associated virus Rep78 protein is mediated by hypophosphorylated pRb

P Saudan1, J Vlach, P Beard

  • 1Swiss Institute for Experimental Cancer Research (ISREC), 1066 Epalinges, Switzerland.

The EMBO Journal
|August 16, 2000
PubMed

Insights

Adeno-associated virus (AAV) Rep78 protein halts cell division by accumulating active retinoblastoma protein (pRb). This novel S-phase arrest mechanism highlights pRb

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Virology

Background:

  • Adeno-associated virus (AAV) exhibits antiproliferative effects on cells.
  • AAV replication proteins (Rep) play a role in viral replication and potentially host cell manipulation.

Purpose of the Study:

  • To investigate the impact of AAV Rep proteins on the cell division cycle.
  • To elucidate the mechanism by which Rep proteins affect cell proliferation and cell cycle progression.

Main Methods:

  • Retroviral vectors were used to express AAV Rep proteins (Rep78, Rep68, Rep52, Rep40) in various cell types.
  • Cell cycle progression was analyzed using flow cytometry and Western blotting for cell cycle regulators.
  • The role of retinoblastoma protein (pRb) in Rep78-mediated cell cycle arrest was assessed using Rb-deficient cells and viral oncoproteins.

Main Results:

  • Rep78 and Rep68 significantly inhibited the growth of primary, immortalized, and transformed cells.
  • Rep68 induced G1 and G2 cell cycle arrest, associated with increased p21 and decreased cyclin-dependent kinase activity.
  • Rep78 caused S-phase arrest, characterized by hypophosphorylated pRb accumulation, and this arrest was dependent on pRb binding by viral proteins E1A and E7.

Conclusions:

  • AAV Rep78 protein arrests cells in S-phase through a novel mechanism involving the accumulation of active pRb.
  • Physiological levels of active pRb can impede S-phase progression, suggesting a broader role in cell cycle regulation.
  • The C-terminal zinc finger domain of Rep78 is critical for its S-phase arresting activity.

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