The inhibitory effects of wheat germ agglutinin and mAb 414 on the nuclear import of all types of U snRNAs indicate that they cross the nuclear envelope through the nuclear pore complex. However, the import of different U snRNAs occurs by kinetically distinct targeting pathways that can be distinguished from one another by the competitive effects of free trimethylguanosine cap dinucleotide (m3GpppG) and P(Lys)-BSA, an efficient synthetic karyophile based on the nuclear localization signal of SV40 large T antigen. The import of U snRNAs that contain 5' m3GpppN caps and are complexed by Sm proteins (U1, U2, U4, and U5) is competed by coinjection with free m3GpppG, indicating a shared transport factor, but not by P(Lys)-BSA. The import of U6 snRNA, which lacks a m3GpppN cap and is not complexed by the Sm proteins, is competed by P(Lys)-BSA but not by free m3GpppG. Thus, by the criterion of kinetic competition, U6 snRNA import is identical to that of the karyophilic proteins P(Lys)-BSA and nucleoplasmin. Uniquely, the import of U3 snRNA, which contains a m3GpppN cap but does not bind Sm proteins is not competed by either free m3GpppG or P(Lys)-BSA. Thus, U3 snRNA appears to be imported by a novel third kinetic pathway.
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15 February 1992
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February 15 1992
Microinjected U snRNAs are imported to oocyte nuclei via the nuclear pore complex by three distinguishable targeting pathways.
N Michaud,
N Michaud
Department of Biology, University of Rochester, New York 14627.
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D Goldfarb
D Goldfarb
Department of Biology, University of Rochester, New York 14627.
Search for other works by this author on:
N Michaud
Department of Biology, University of Rochester, New York 14627.
D Goldfarb
Department of Biology, University of Rochester, New York 14627.
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1992) 116 (4): 851–861.
Citation
N Michaud, D Goldfarb; Microinjected U snRNAs are imported to oocyte nuclei via the nuclear pore complex by three distinguishable targeting pathways.. J Cell Biol 15 February 1992; 116 (4): 851–861. doi: https://doi.org/10.1083/jcb.116.4.851
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