Nuclear localization of human DNA mismatch repair protein exonuclease 1 (hEXO1)

Nina Ostergaard Knudsen, Finn Cilius Nielsen, Lena Vinther, Ronni Bertelsen, Steen Holten-Andersen, Sascha Emilie Liberti, Robert Hofstra, Krista Kooi, Lene Juel Rasmussen*

*Corresponding author for this work

    Research output: Contribution to journalArticleAcademicpeer-review

    30 Citations (Scopus)

    Abstract

    Human exonuclease 1 (hEXO1) is implicated in DNA mismatch repair (MMR) and mutations in hEXO1 may be associated with hereditary nonpolyposis colorectal cancer (HNPCC). Since the subcellular localization of MMR proteins is essential for proper MMR function, we characterized possible nuclear localization signals (NLSs) in hEXO1. Using fluorescent fusion proteins, we show that the sequence (KRPR421)-K-418, which exhibit strong homology to other monopartite NLS sequences, is responsible for correct nuclear localization of hEXO1. This NLS sequence is located in a region that is also required for hEXO1 interaction with hMLH1 and we show that defective nuclear localization of hEXO1 mutant proteins could be rescued by hMLH1 or hMSH2. Both hEXO1 and hMLH1 form complexes with the nuclear import factors importin beta/alpha 1,3,7 whereas hMSH2 specifically recognizes importin beta/alpha 3. Taken together, we infer that hEXO1, hMLH1 and hMSH2 form complexes and are imported to the nucleus together, and that redundant NLS import signals in the proteins may safeguard nuclear import and thereby MMR activity.

    Original languageEnglish
    Pages (from-to)2609-2619
    Number of pages11
    JournalNucleic Acids Research
    Volume35
    Issue number8
    DOIs
    Publication statusPublished - Apr-2007

    Keywords

    • SACCHAROMYCES-CEREVISIAE EXO1
    • HUMAN MUTL-ALPHA
    • LARGE-T-ANTIGEN
    • COLORECTAL-CANCER
    • IMPORTIN-ALPHA
    • GERMLINE MUTATIONS
    • IN-VIVO
    • GENE
    • IDENTIFICATION
    • RECOGNITION

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