Pirh2 interacts with and ubiquitylates signal recognition particle receptor .BETA. subunit
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Pirh2 is a RING finger type ubiquitin ligase which ubiquitylates various proteins including p53, p27<SUP><I>Kip1</I></SUP>, HDAC1, and ε-COP. In this study, we identified signal recognition particle receptor β subunit (SRβ), an integral membrane protein of the endoplasmic reticulum (ER), as a novel Pirh2-interacting protein by yeast two-hybrid screening. We confirmed that Pirh2 interacted with SRβ in mammalian cells. An immunofluorescent staining revealed that Pirh2 colocalized with SRβ in the ER. Pirh2 poly-ubiquitylated SRβ in an intact RING finger domain-dependent manner <I>in vivo</I> and <I>in vitro</I>. Unexpectedly, different from other Pirh2 substrates, neither overexpression of Pirh2 nor depletion of cellular Pirh2 affected SRβ protein stability. Pirh2 preferentially utilized lysine residues 6 and 29 of the ubiquitin to mediate the formation of polyubiquitin chains on SRβ. These results suggest that Pirh2 may regulate SRβ function by mediating poly-ubiquitylation of SRβ without affecting the stability of SRβ protein per se.
- Biomedical Research
Biomedical Research 29(1), 53-60, 2008
Biomedical Research Press