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Updated: Jul 3, 2026

Visualization and Quantitative Analysis of Genotoxin-Induced PARP1/PARP2 Activation in Cells Using a Fluorescent Fusion Protein-Based Reporter
Published on: April 17, 2026
Importin alpha binding and nuclear localization of PARP-2 is dependent on lysine 36, which is located within a
Sandra S Haenni1, Matthias Altmeyer, Paul O Hassa
1Institute of Veterinary Biochemistry and Molecular Biology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland. haennis@vetbio.uzh.ch
Background:
The enzymes responsible for the synthesis of poly-ADP-ribose are named poly-ADP-ribose polymerases (PARP). PARP-2 is a nuclear protein, which regulates a variety of cellular functions that are mainly controlled by protein-protein interactions. A previously described non-conventional bipartite nuclear localization sequence (NLS) lies in the amino-terminal DNA binding domain of PARP-2 between amino acids 1-69; however, this targeting sequence has not been experimentally examined or validated.
Results:
Using a site-directed mutagenesis approach, we found that lysines 19 and 20, located within a previously described bipartite NLS, are not required for nuclear localization of PARP-2. In contrast, lysine 36, which is located within a predicted classical monopartite NLS, was required for PARP-2 nuclear localization. While wild type PARP-2 interacted with importin alpha3 and to a very weak extent with importin alpha1 and importin alpha5, the mutant PARP-2 (K36R) did not interact with importin alpha3, providing a molecular explanation why PARP-2 (K36R) is not targeted to the nucleus.
Conclusion:
Our results provide strong evidence that lysine 36 of PARP-2 is a critical residue for proper nuclear targeting of PARP-2 and consequently for the execution of its biological functions.
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