Knauf J A, Pendergrass S H, Marrone B L, Strniste G F, MacInnes M A, Park M S
Life Sciences Division, Los Alamos National Laboratory, NM 87545, USA.
Mutat Res. 1996 May 15;363(1):67-75. doi: 10.1016/0921-8777(95)00062-3.
We report here evidence for the mechanism of nuclear localization of XPG nuclease in human cells. Several candidate nuclear localization signal (NLS) peptides have been proposed for XPG protein. We have identified XPG peptides containing functional NLS and a potential nuclear retention signal (NRS) using in situ immunofluorescene localization of transiently expressed beta-galactosidase fusion proteins. Two XPG regions with putative NLS [amino acid (AA) coordinates: NLS-B (AA 1057-1074) and NLS-C (AA 1171-1185)] were each shown to independently localize the beta-gal extensively (> 80%) to the nucleus of HeLa cells. The C-terminus peptide containing NLS-C, an NLS conserved evolutionarily between yeasts and humans, also directed sub-localization of beta-galactosidase to intranuclear foci reminiscent of native XPG protein, as well as to peri-nucleolar regions. Peptides in the putative XPG 'NLS domain' (AA approximately 1051-1185) apparently function in concert for nuclear localization and also for retention of XPG in nuclear matrix-associated foci. Evidence presented elsewhere (Park et al., 1995) indicates that the peptide containing NLS-C (AA 1146-1185) also regulates the dynamic localization of XPG in the nucleus following UV-irradiation.
我们在此报告人类细胞中XPG核酸酶核定位机制的证据。已经提出了几种XPG蛋白的候选核定位信号（NLS）肽段。我们通过瞬时表达的β-半乳糖苷酶融合蛋白的原位免疫荧光定位，鉴定出含有功能性NLS和潜在核滞留信号（NRS）的XPG肽段。两个具有假定NLS的XPG区域[氨基酸（AA）坐标：NLS-B（AA 1057 - 1074）和NLS-C（AA 1171 - 1185）]各自显示能使β-半乳糖苷酶广泛（> 80%）定位于HeLa细胞的细胞核。包含NLS-C的C末端肽段，这是一种在酵母和人类之间进化保守的NLS，还能将β-半乳糖苷酶亚定位到类似于天然XPG蛋白的核内病灶以及核仁周围区域。假定的XPG“NLS结构域”（AA约1051 - 1185）中的肽段显然协同作用于核定位，并使XPG保留在核基质相关病灶中。其他地方（Park等人，1995年）提出的证据表明，含有NLS-C（AA 1146 - 1185）的肽段在紫外线照射后也能调节XPG在细胞核中的动态定位。
