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Leucine methylation of protein phosphatase PP4C at C-terminal is critical for its cellular functions

JungJin Lee1, Dong-Hyun Lee1

  • 1Department of Biological Sciences, College of Science, Chonnam National University, Gwangju 500-757, Republic of Korea.

Biochemical and Biophysical Research Communications
|August 19, 2014
PubMed
Abstract

Insights

Protein phosphatase 4 catalytic subunit (PP4C) methylation at C-terminal L307 is crucial for its function in DNA double-strand break (DSB) repair. This modification regulates PP4C activity and interaction with target proteins, impacting homologous recombination and non-homologous end joining pathways.

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Biochemistry

Background:

  • Protein phosphatase 4 (PP4) regulates DNA double-strand break (DSB) repair and cell cycle.
  • PP4 targets proteins like H2AX, RPA2, KAP-1, and 53BP1.
  • Regulation of PP4 itself remains largely uncharacterized.

Purpose of the Study:

  • To investigate the regulation of Protein phosphatase 4 catalytic subunit (PP4C).
  • To determine the role of PP4C methylation at C-terminal leucine 307 (L307) in its cellular functions.
  • To explore the impact of non-methylated PP4C on DNA DSB repair pathways.

Main Methods:

  • Utilized a methylated-leucine specific antibody to examine PP4C methylation at L307.
  • Employed a PP4C L307A mutant to study the effects of non-methylated PP4C.
  • Performed immunoprecipitation, immunofluorescence, and DNA DSB repair assays.

Main Results:

  • PP4C is methylated at a C-terminal leucine residue in vivo, which is vital for PP4-mediated cellular functions.
  • The PP4C L307A mutant exhibited significantly reduced dephosphorylation activity towards target proteins.
  • Loss of L307 methylation disrupted the interaction of PP4C with regulatory subunits (R1, R2, R3α/β), leading to target protein dissociation.
  • PP4C L307A mutant impaired homologous recombination (HR) and non-homologous end joining (NHEJ) DNA DSB repair pathways, mimicking PP4C depletion.

Conclusions:

  • Identified the key C-terminal L307 site for PP4C methylation.
  • Established the physiological significance of PP4C methylation in regulating its function.
  • Demonstrated that PP4C methylation is essential for its role in DNA DSB repair.
Keywords:
DNA damage responseDouble-strand DNA breaks repairHomologous recombinationLeucine methylationNon-homologous end joiningProtein phosphatase 4

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