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Pirh2 interacts with and ubiquitylates signal recognition particle receptor beta subunit

Kenji Abe1, Takayuki Hattori, Tomoyasu Isobe

  • 1Department of Biochemistry 1, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan.

Biomedical Research (Tokyo, Japan)
|March 18, 2008
PubMed

Insights

Pirh2, a ubiquitin ligase, interacts with the signal recognition particle receptor beta subunit (SRbeta) in the endoplasmic reticulum. Pirh2 poly-ubiquitylates SRbeta, potentially regulating its function without altering protein stability.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Pirh2 (RING finger protein 2) is a ubiquitin ligase known to target various proteins for degradation or altered function.
  • The signal recognition particle receptor beta subunit (SRbeta) is crucial for protein translocation into the endoplasmic reticulum (ER).

Purpose of the Study:

  • To identify novel interacting partners of Pirh2.
  • To investigate the functional consequences of Pirh2 interaction with SRbeta.

Main Methods:

  • Yeast two-hybrid screening to identify Pirh2-interacting proteins.
  • Co-immunoprecipitation and immunofluorescence to confirm Pirh2-SRbeta interaction and localization.
  • In vitro and in vivo ubiquitylation assays to assess Pirh2's effect on SRbeta.

Main Results:

  • SRbeta was identified as a novel binding partner of Pirh2.
  • Pirh2 and SRbeta colocalize within the ER.
  • Pirh2 poly-ubiquitylates SRbeta in a RING finger domain-dependent manner, specifically utilizing K6 and K29 linkages on ubiquitin.
  • SRbeta protein stability was not affected by Pirh2 overexpression or depletion.

Conclusions:

  • Pirh2 interacts with and poly-ubiquitylates SRbeta at the ER.
  • This ubiquitylation likely modulates SRbeta function rather than affecting its protein stability.
  • Pirh2's role in regulating ER protein translocation may involve non-degradative ubiquitylation of SRbeta.

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