Michaud N, Goldfarb D S
Department of Biology, University of Rochester, New York 14627.
J Cell Biol. 1991 Jan;112(2):215-23. doi: 10.1083/jcb.112.2.215.
Protein import to the nucleus is a signal-mediated process that exhibits saturation kinetics. We investigated whether signal bearing proteins compete with U2 and U6 snRNPs during import. When injected into Xenopus oocytes, saturating concentrations of P(Lys)-BSA, a protein bearing multiple nuclear localization signals from SV40 large T-antigen, reduce the rate of [125I]P(Lys)-BSA and of [125I]nucleoplasmin import, consistent with their competing for and sharing the same limiting component of the import apparatus. In contrast, saturating concentrations of P(Lys)-BSA do not reduce the rate of HeLa [32P]U2 snRNP assembly or import. The import of U6 snRNP is also competed by P(Lys)-BSA. We conclude that U2 snRNP is imported into oocyte nuclei by a kinetic pathway that is distinct from the one followed by P(Lys)-BSA, nucleoplasmin, and U6 snRNP.
蛋白质向细胞核的转运是一个信号介导的过程，表现出饱和动力学。我们研究了携带信号的蛋白质在转运过程中是否与U2和U6 snRNP竞争。当将饱和浓度的P（Lys）-BSA（一种携带来自SV40大T抗原的多个核定位信号的蛋白质）注射到非洲爪蟾卵母细胞中时，会降低[125I]P（Lys）-BSA和[125I]核质蛋白的转运速率，这与其竞争并共享转运装置的同一限制成分一致。相比之下，饱和浓度的P（Lys）-BSA不会降低HeLa [32P]U2 snRNP组装或转运的速率。U6 snRNP的转运也会被P（Lys）-BSA竞争。我们得出结论，U2 snRNP通过一种与P（Lys）-BSA、核质蛋白和U6 snRNP所遵循的途径不同的动力学途径被转运到卵母细胞核中。
