Cleaving the oxidative repair protein Ape1 enhances cell death mediated by granzyme A


The cytolytic T lymphocyte protease granzyme A (GzmA) initiates a caspase-independent cell death pathway. Here we report that the rate-limiting enzyme of DNA base excision repair, apurinic endonuclease-1 (Ape1), which is also known as redox factor-1 (Ref-1), binds to GzmA and is contained in the SET complex, a macromolecular complex of 270–420 kDa that is associated with the endoplasmic reticulum and is targeted by GzmA during cell-mediated death. GzmA cleaves Ape1 after Lys31 and destroys its known oxidative repair functions. In so doing, GzmA may block cellular repair and force apoptosis. In support of this, cells with silenced Ape1 expression are more sensitive, whereas cells overexpressing noncleavable Ape1 are more resistant, to GzmA-mediated death.

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Figure 1: Ape1 co-elutes with the SET complex.
Figure 2: Ape1 interacts and colocalizes with pp32 and SET.
Figure 3: Ape1 is a substrate of GzmA but not GzmB.
Figure 4: GzmA and PFP treatment of HeLa cells causes degradation of Ape1.
Figure 5: GzmA disrupts the AP endonuclease and redox activities of Ape1.
Figure 6: Silencing of Ape1 expression enhances GzmA-mediated cytolysis and DNA nicking.
Figure 7: Overexpressing noncleavable Ape1 reduces GzmA-induced cell death.


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We thank M. Russo for technical support; B. Demple, D. Oh, X.-F. Yang, L. Shi and K. Kaznatcheev for suggestions; and the National Center for Cell Culture for preparing K562 cell lysates to purify the SET complex. This work was supported by a grant from the National Institutes of Health (NIH) to J.L. and the NIH-supported Dana Farber Cancer Institute, Beth Israel Deaconess Medical Center and Children's Hospital Center for AIDS Research.

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Correspondence to Judy Lieberman.

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Fan, Z., Beresford, P., Zhang, D. et al. Cleaving the oxidative repair protein Ape1 enhances cell death mediated by granzyme A. Nat Immunol 4, 145–153 (2003).

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