Journal
MOLECULAR AND CELLULAR BIOLOGY
Volume 23, Issue 4, Pages 1292-1303Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/MCB.23.4.1292-1303.2003
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- NIDDK NIH HHS [R01-DK52054, R01 DK052054] Funding Source: Medline
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The growth arrest and DNA damage-inducible protein, GADD34, associates with protein phosphatase 1 (PP1) and promotes in vitro dephosphorylation of the alpha subunit of eukaryotic translation initiation factor 2, (eIF-2alpha). In this report, we show that the expression of human GADD34 in cultured cells reversed eIF-2alpha phosphorylation induced by thapsigargin and tunicamycin, agents that promote protein unfolding in the endoplasmic reticulum (ER). GADD34 expression also reversed eIF-2alpha phosphorylation induced by okadaic acid but not that induced by another phosphatase inhibitor, calyculin A (CA), which is a result consistent with PP1 being a component of the GADD34-assembled eIF-2alpha phosphatase. Structure-function studies identified a bipartite C-terminal domain in GADD34 that encompassed a canonical PP1-binding motif, KVRF, and a novel RARA sequence, both of which were required for PP1 binding. N-terminal deletions of GADD34 established that while PP1 binding was necessary, it was not sufficient to promote eIF-2alpha dephosphorylation in cells. Imaging of green fluorescent protein (GFP)-GADD34 proteins showed that the N-terminal 180 residues directed the localization of GADD34 at the ER and that GADD34 targeted the a isoform of PP1 to the ER. These data provide new insights into the mode of action of GADD34 in assembling an ER-associated eIF-2alpha phosphatase that regulates protein translation in mammalian cells.
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