Abstract

Dephosphorylation of eukaryotic translation initiation factor 2a (eIF2a) restores protein synthesis at the waning of stress responses and requires a PP1 catalytic subunit and a regulatory subunit, PPP1R15A/GADD34 or PPP1R15B/CReP. Surprisingly, PPP1R15-PP1 binary complexes reconstituted in vitro lacked substrate selectivity. However, selectivity was restored by crude cell lysate or purified G-actin, which joined PPP1R15-PP1 to form a stable ternary complex. In crystal structures of the non-selective PPP1R15B-PP1G complex, the functional core of PPP1R15 made multiple surface contacts with PP1G, but at a distance from the active site, whereas in the substrate-selective ternary complex, actin contributes to one face of a platform encompassing the active site. Computational docking of the N-terminal lobe of eIF2a at this platform placed phosphorylated serine 51 near the active site. Mutagenesis of predicted surface-contacting residues enfeebled dephosphorylation, suggesting that avidity for the substrate plays an important role in imparting specificity on the PPP1R15B-PP1G-actin ternary complex.

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Author details

  1. Ruming Chen

    Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
    Competing interests
    No competing interests declared.
  2. Cláudia Rato

    Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
    Competing interests
    No competing interests declared.
  3. Yahui Yan

    Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
    Competing interests
    No competing interests declared.
  4. Ana Crespillo-Casado

    Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
    Competing interests
    No competing interests declared.
  5. Hanna J Clarke

    Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
    Competing interests
    No competing interests declared.
  6. Heather P Harding

    Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
    Competing interests
    No competing interests declared.
  7. Stefan J Marciniak

    Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
    Competing interests
    No competing interests declared.
  8. Randy J Read

    Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
    Competing interests
    No competing interests declared.
  9. David Ron

    Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
    For correspondence
    dr360@medschl.cam.ac.uk
    Competing interests
    David Ron, Reviewing editor, eLife.

Reviewing Editor

  1. W James Nelson, Stanford University, United States

Version history

  1. Received: September 23, 2014
  2. Accepted: March 12, 2015
  3. Accepted Manuscript published: March 16, 2015 (version 1)
  4. Version of Record published: April 13, 2015 (version 2)

Copyright

© 2015, Chen et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Ruming Chen
  2. Cláudia Rato
  3. Yahui Yan
  4. Ana Crespillo-Casado
  5. Hanna J Clarke
  6. Heather P Harding
  7. Stefan J Marciniak
  8. Randy J Read
  9. David Ron
(2015)
G-actin provides substrate-specificity to eukaryotic initiation factor 2α holophosphatases
eLife 4:e04871.
https://doi.org/10.7554/eLife.04871

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https://doi.org/10.7554/eLife.04871

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