Karyopherin- alpha 2 Protein Interacts with Chk2 and Contributes to Its Nuclear Import

• Published in: The Journal of biological chemistry Vol. 278; no. 43; pp. 42346 - 42351
• Main Authors: Zannini, L, Lecis, D, Lisanti, S, Benetti, R, Buscemi, G, Schneider, C, Delia, D
• Format: Journal Article
• Language: English
• Published: 24.10.2003
• Subjects: Chk2 protein; karyopherin ^a
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M303304200

Chk2 is a nuclear protein kinase involved in the DNA damage-induced ataxia telangiectasia mutated-dependent checkpoint arrest at multiple cell cycle phases. Searching for Chk2-binding proteins by a yeast two-hybrid system, we identified a strong interaction with karyopherin- alpha 2 (KPNA-2), a gene product involved in active nuclear import of proteins bearing a nuclear localization signal (NLS). This finding was confirmed by glutathione S- transferase pull-down and co-immunoprecipitation assays. Of the three predicted Chk2 NLSs, located at amino acids 179-182 (NLS-1), 240-256 (NLS-2), and 515-522 (NLS-3), only the latter mediated the interaction with KPNA-2 in the yeast two- hybrid system, and in particular with its C terminus. Unlike mutations in NLS-1 or NLS-2, which left the nuclear localization of Chk2 unaffected, mutations in NLS-3 caused a cytoplasmic relocalization, indicating that the NLS-3 motif acts indeed as NLS for Chk2 in vivo. Finally, co-transfection experiments with green fluorescent protein (GFP)-Chk2 and wild type or mutant KPNA-2 confirmed the role of KPNA-2 in nuclear import of Chk2.