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Post-translationally modified S12, absent in transformed breast epithelial cells, is not associated with the 26S proteasome and is induced by proteasome inhibitor.

Abstract：

:The 26S proteasome, consisting of the 20S core and 19S regulatory complexes, regulates intracellular protein concentration through proteolytic degradation of targeted substrates. Composition of the 19S regulatory complex as well as posttranslational modifications of the 19S subunits can effectively regulate the activity of the 26S proteasome. Aberrant activity of the 26S proteasome affects the cell cycle, apoptosis and other cellular processes related to cancer. Recent data show an additional proteasome-independent role of 19S subunits in transcriptional regulation. S12 (Rpn8), the human homologue of mouse Mov-34, is a non-ATPase 19S regulatory subunit of the 26S proteasome. Previous studies have identified phosphorylated S12. In our study, we identify a modified S12 isoform (S12-M) with distinct biochemical properties. The S12-M isoform was found in 6 normal, but not 4 transformed, breast epithelial cell lines. Modification of S12 protein can be induced in vitro by addition of the proteasome inhibitor PSI. Modified and unmodified S12 have similar mass, but different isoelectric points, consistent with phosphorylation. In normal cells, unmodified S12 associates with the 26S proteasome, while modified S12-M does not. Whereas transformed cell line nuclei contain neither S12 isoform, S12-M is predominantly cytosolic in normal cells, with the unmodified S12 present in both the nuclei and cytosol. Together with the role of 19S subunits in transcriptional regulation, homology between S12 and eIF3 and TFIIH subunits, coelution with immunoproteasome subunits, and differential posttranslational modification and nuclear localization, these data suggest a differential nuclear function of modified and unmodified S12 in cancer.

journal_name

Int J Cancer

journal_title

International journal of cancer

authors

Thompson HG,Harris JW,Brody JP

doi

10.1002/ijc.20261

keywords:

subject

Has Abstract

pub_date

2004-09-01 00:00:00

pages

338-47

issue

eissn

0020-7136

issn

1097-0215

journal_volume

111

pub_type

杂志文章

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Post-translationally modified S12, absent in transformed breast epithelial cells, is not associated with the 26S proteasome and is induced by proteasome inhibitor.