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Regulation of MAP kinases by the VHR dual-specific phosphatase: implications for cell growth and differentiation

Fabio Cerignoli1, Souad Rahmouni, Ze'ev Ronai

  • 1The Burnham Institute for Medical Research, La Jolla, California 92037, USA.

Cell Cycle (Georgetown, Tex.)
|October 3, 2006
PubMed

Insights

The Vaccinia H1-related (VHR) phosphatase regulates cell cycle progression by controlling Erk and Jnk kinase activity. Loss of VHR leads to cell cycle arrest and senescence, highlighting VHR's crucial role in cell fate.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Transient activation of Erk and Jnk kinases promotes cell growth.
  • Prolonged activation of Erk and Jnk can induce cell cycle arrest, differentiation, and senescence.
  • The role of specific phosphatases in regulating these kinase activities during the cell cycle is not fully understood.

Purpose of the Study:

  • To investigate the role of the Vaccinia H1-related (VHR) dual-specific phosphatase in cell cycle regulation.
  • To determine how VHR expression and activity affect Erk and Jnk kinase signaling throughout the cell cycle.
  • To elucidate the contribution of VHR to cell cycle arrest, differentiation, and senescence phenotypes.

Main Methods:

  • Analysis of VHR expression during cell cycle progression.
  • Generation and characterization of VHR-deficient cells.
  • Assessment of Erk and Jnk kinase activity in VHR-deficient cells.
  • Gene expression profiling in VHR-deficient cells.
  • Inhibition of Jnk and Erk signaling pathways in VHR-deficient cells.

Main Results:

  • VHR expression fluctuates during cell cycle progression, impacting Erk and Jnk activity in a cell cycle-dependent manner.
  • VHR-deficient cells exhibited cell cycle arrest at the G(1)/S and G(2)/M transitions and displayed senescence phenotypes.
  • Loss of VHR led to upregulation of p21(Cip/Waf1) and downregulation of genes involved in cell cycle regulation, DNA replication, transcription, and mRNA processing.
  • Serum-induced Jnk and Erk activation was elevated in VHR-deficient cells and was essential for G(1)/S and G(2)/M arrest, with inhibition of these kinases attenuating the blocks.

Conclusions:

  • VHR acts as a critical regulator of Jnk and Erk activity during cell cycle progression.
  • VHR's function is essential for preventing aberrant cell cycle arrest, differentiation, and senescence.
  • VHR provides a key regulatory layer in mitogen-activated protein kinase signaling pathways controlling cell fate.

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