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Proc Natl Acad Sci U S A. 2018 Jul 10;115(28):E6477-E6486. doi: 10.1073/pnas.1722299115. Epub 2018 Jun 22.

PIP30/FAM192A is a novel regulator of the nuclear proteasome activator PA28γ.

Author information

1
Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), Université de Montpellier, CNRS, 34090 Montpellier, France.
2
Institut de Pharmacologie et Biologie Structurale (IPBS), CNRS, Université de Toulouse-Université Paul Sabatier, 31062 Toulouse, France.
3
Montpellier Ressources Imagerie (MRI) Facility, Biocampus UMS3426, CNRS, 34090 Montpellier, France.
4
Institut de Recherche en Cancérologie de Montpellier (IRCM) - INSERM U1194, Institut Régional du Cancer de Montpellier, Université de Montpellier, F-34298 Montpellier, France.
5
Centre for Gene Regulation and Expression, School of Life Sciences, DD1 5HL Dundee, United Kingdom.
6
Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), Université de Montpellier, CNRS, 34090 Montpellier, France; severine.boulon@crbm.cnrs.fr Marie-Pierre.Bousquet@ipbs.fr olivier.coux@crbm.cnrs.fr.
7
Institut de Pharmacologie et Biologie Structurale (IPBS), CNRS, Université de Toulouse-Université Paul Sabatier, 31062 Toulouse, France; severine.boulon@crbm.cnrs.fr Marie-Pierre.Bousquet@ipbs.fr olivier.coux@crbm.cnrs.fr.

Abstract

PA28γ is a nuclear activator of the 20S proteasome involved in the regulation of several essential cellular processes, such as cell proliferation, apoptosis, nuclear dynamics, and cellular stress response. Unlike the 19S regulator of the proteasome, which specifically recognizes ubiquitylated proteins, PA28γ promotes the degradation of several substrates by the proteasome in an ATP- and ubiquitin-independent manner. However, its exact mechanisms of action are unclear and likely involve additional partners that remain to be identified. Here we report the identification of a cofactor of PA28γ, PIP30/FAM192A. PIP30 binds directly and specifically via its C-terminal end and in an interaction stabilized by casein kinase 2 phosphorylation to both free and 20S proteasome-associated PA28γ. Its recruitment to proteasome-containing complexes depends on PA28γ and its expression increases the association of PA28γ with the 20S proteasome in cells. Further dissection of its possible roles shows that PIP30 alters PA28γ-dependent activation of peptide degradation by the 20S proteasome in vitro and negatively controls in cells the presence of PA28γ in Cajal bodies by inhibition of its association with the key Cajal body component coilin. Taken together, our data show that PIP30 deeply affects PA28γ interactions with cellular proteins, including the 20S proteasome, demonstrating that it is an important regulator of PA28γ in cells and thus a new player in the control of the multiple functions of the proteasome within the nucleus.

KEYWORDS:

Cajal bodies; FAM192A; PA28γ; nuclear proteolysis; proteasome

PMID:
29934401
PMCID:
PMC6048556
DOI:
10.1073/pnas.1722299115
[Indexed for MEDLINE]
Free PMC Article

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