title: Characterization of the nuclear localization signal in the DNA helicase involved in Werner's syndrome.
abstract: The nuclear localization signal (NLS) of the DNA helicase involved in Werner's syndrome (WS) was studied. Previously, we noted that the C-terminal region of WS helicase contains the NLS. In this study, we generated in HeLa cells various chimeric proteins consisting of the N-terminal tagged with an enhanced green fluorescent protein and the C-terminal fragments of the WS helicase that were truncated either from N- or C-termini, and we examined the ability of fragments to transfer the fusion proteins to the nucleoplasm by fluorescence microscopy. A small C-proximal region containing 34 amino acid residues (residues 1369-1402) was found to contain full nuclear migration activities. Subsequent amino acid substitution experiments showed that a sequence of three positively charged amino acids (Lys1371-Arg1372-Arg1373) in this region are particularly important. Similar sequence has previously been defined as the nuclear localization signal of SV-40 large T antigen that also acts as a viral DNA helicase. Conservation of this motif was found in the C-terminal regions of the other RecQ type DNA helicases, including murine WS helicase, yeast sgs1 and rqh+1 and human Bloom syndrome DNA helicases.
authors.affiliation: AGENE Research Institute, Kamakura, Kanagawa 247, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Matsumoto
authors.forename: O
authors.initials: O
authors.lastname: Imamura
authors.forename: M
authors.initials: M
authors.lastname: Goto
authors.forename: Y
authors.initials: Y
authors.lastname: Furuichi
mesh_terms: D000251:Adenosine Triphosphatases; D019943:Amino Acid Substitution; D000818:Animals; D002467:Cell Nucleus; D004265:DNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D019913:Nuclear Localization Signals / Q000235:genetics; D051381:Rats; D053484:RecQ Helicases; D014898:Werner Syndrome / Q000201:enzymology*
chemical_list: D019913:Nuclear Localization Signals; D000251:Adenosine Triphosphatases; C506725:RECQL protein, human; D004265:DNA Helicases; D053484:RecQ Helicases