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

TY - JOUR

T1 - Nuclear localization of human DNA mismatch repair protein exonuclease 1 (hEXO1)

AU - Knudsen, Nina Østergaard

AU - Nielsen, Finn Cilius

AU - Vinther, Lena

AU - Bertelsen, Ronni

AU - Holten-Andersen, Steen

AU - Liberti, Sascha Emilie

AU - Hofstra, Robert

AU - Kooi, Krista

AU - Rasmussen, Lene Juel

PY - 2007

Y1 - 2007

N2 - 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 418KRPR421, 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/alpha1,3,7 whereas hMSH2 specifically recognizes importin beta/alpha3. 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.

AB - 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 418KRPR421, 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/alpha1,3,7 whereas hMSH2 specifically recognizes importin beta/alpha3. 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.

KW - Adaptor Proteins, Signal Transducing

KW - Animals

KW - Cell Line

KW - Cell Nucleus

KW - DNA Mismatch Repair

KW - DNA Repair Enzymes

KW - Exodeoxyribonucleases

KW - Humans

KW - Karyopherins

KW - Mice

KW - MutS Homolog 2 Protein

KW - Nuclear Localization Signals

KW - Nuclear Proteins

U2 - 10.1093/nar/gkl1166

DO - 10.1093/nar/gkl1166

M3 - Journal article

C2 - 17426132

SN - 0305-1048

VL - 35

SP - 2609

EP - 2619

JO - Nucleic Acids Research

JF - Nucleic Acids Research

IS - 8

ER -