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Gpn3 is polyubiquitinated on lysine 216 and degraded by the proteasome in the cell nucleus in a Gpn1‐inhibitable manner
Author(s) -
MéndezHernández Lucía E.,
RobledoRivera Angelica Y.,
MacíasSilva Marina,
Calera Mónica R.,
SánchezOlea Roberto
Publication year - 2017
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1002/1873-3468.12883
Subject(s) - ubiquitin , proteasome , flag (linear algebra) , microbiology and biotechnology , cytoplasm , nucleus , hek 293 cells , lysine , protein degradation , chemistry , nuclear localization sequence , biochemistry , biology , gene , mathematics , amino acid , pure mathematics , algebra over a field
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 MG 132, Gpn3‐Flag was polyubiquitinated on K216, but not K189, in HEK 293T cells. Gpn3‐Flag exhibited nucleo‐cytoplasmic shuttling, but polyubiquitination and proteasomal degradation of Gpn3‐Flag occurred only in the cell nucleus. Polyubiquitination‐deficient Gpn3‐Flag K216R displayed a longer half‐life than Gpn3‐Flag in two cell lines. Interestingly, Gpn1‐ EYFP inhibited 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.