5 years ago

Gpn3 is polyubiquitinated on lysine 216 and degraded by the proteasome in the cell nucleus in a Gpn1-inhibitable manner

Angelica Y. Robledo-Rivera, Marina Macías-Silva, Roberto Sánchez-Olea, Lucía E. Méndez-Hernández, Mónica R. Calera
Gpn1 associates with Gpn3, and both are required for RNA polymerase II nuclear targeting. Global studies have identified by mass spectrometry that human Gpn3 is ubiquitinated on lysines 189 and 216. Our goals here were to determine the type, physiological importance, and regulation of Gpn3 ubiquitination. After inhibiting the proteasome with MG132, Gpn3-Flag is polyubiquitinated on K216, but not K189, in HEK293T cells. Gpn3-Flag exhibits nucleo-cytoplasmic shuttling, but polyubiquitination and proteasomal degradation of Gpn3-Flag occurrs only in the cell nucleus. Polyubiquitination-deficient Gpn3-Flag K216R displays a longer half-life than Gpn3-Flag in two cell lines. Interestingly, Gpn1-EYFP inhibits Gpn3-Flag polyubiquitination in a dose-dependent manner. In conclusion, Gpn1-inhibitable, nuclear polyubiquitination on lysine 216 regulates the half-life of Gpn3 by tagging it for proteasomal degradation. This article is protected by copyright. All rights reserved.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/1873-3468.12883

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