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Diversity in the signals required for nuclear accumulation of U snRNPs and variety in the pathways of nuclear transport

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Abstract

The requirements for nuclear targeting of a number of U snRNAs have been studied by analyzing the behavior of in vitro-generated transcripts after microinjection into the cytoplasm of Xenopus oocytes. Like the previously studied U1 snRNA, U2 snRNA is excluded from the nucleus when it does not have the 2,2,7mGpppN cap structure typical of the RNA polymerase II (pol II)-transcribed U snRNAs. Surprisingly, two other pol II-transcribed U snRNAs, U4 and U5, have a much less stringent requirement for the trimethyl cap structure. The gamma- monomethyl triphosphate cap structure of the RNA polymerase III- transcribed U6 snRNA, on the other hand, is shown not to play a role in nuclear targeting. Wheat germ agglutinin, which is known to prevent the import of many proteins into the nucleus, inhibits nuclear uptake of U6, but not of U1 or U5 snRNAs. Conversely, a 2,2,7mGpppG dinucleotide analogue of the trimethyl cap structure inhibits transport of the pol II U snRNAs, but does not detectably affect the transport of either U6 snRNA or a karyophilic protein. From these results it can be deduced that U6 enters the nucleus by a pathway similar or identical to that used by karyophilic proteins. The composite nuclear localization signals of the trimethyl cap-containing U snRNPs, however, do not function in the same way as previously defined nuclear targeting signals

Topics: Articles
Publisher: The Rockefeller University Press
OAI identifier: oai:pubmedcentral.nih.gov:2288978
Provided by: PubMed Central
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    Citations

    1. (1988). 5-globin mRNAs capped with m7G, rn2,7G or m2,2,7G differ in intrinsic translation efficiency.
    2. (1989). 7-Monomethyl phosphate: a cap structure in spliceosomal 136 small nuclear RNA.
    3. (1987). A monoclonai antibody against 2,2,7-trimethylgnanosine that reacts with intact, class U, small nuclear ribonuclcoproteins as well as with 7-methylguanosine-capped RNAs.
    4. (1989). An abundant 156 snRNP found in germ cells and embryos ofXenepus laevis.
    5. (1990). An essential signaling role for the m3G cap in the transport of U1 snRNP to the nucleus. Science (Wash.
    6. (1986). Cap trimethylation of U snRNA is cy~plasmic and dependent on U snRNP protein binding.
    7. (1990). Cell biology of the snRNP particles.
    8. (1985). Chemical synthesis and characterization of 7-methylguanosine cap anaiognes.
    9. (1970). Cleavage of structural proteins during the assembly of the head of bacteriophage I"4.
    10. (1990). Domains of U4 and U6 snRNAs required for snRNP assembly and splicing complementation in Xenopus oocytes.
    11. (1986). Formation of the 3'-end of UI snRNA requires compatible snRNA promoter elements.
    12. (1987). Functional characterization ofX. laevis U5 snRNA genes.
    13. (1988). Functions of the abundant U snRNPs.
    14. (1989). I_13, U8, and UI 3 comprise a new class of mammalian snRN'Ps localized in the cell nucleolus.
    15. (1987). In vitro assembly of UI snRNPs.
    16. (1987). Inhibition of in vitro nuclear transport by a lectin that binds to nuclear pores.
    17. (1988). Inhibition of nuclear accumulation of karyephilie proteins in living cells by microinjection of the lectin wheat germ agglutinin.
    18. (1985). mRNA cap binding proteins: essential factors for initiating translation.
    19. (1991). Multiple pathways in nuclear transport: the import of U2 snRNP occurs by a novel kinetic pathway.
    20. (1985). Nuclear segregation of U2 snRNA requires binding of specific snRNP proteins.
    21. (1986). Protein import into the cell nucleus.
    22. (1989). small nuclear ribonucleeprotein U5 shows a surprisingly complex protein composition.
    23. (1988). snRNP proteins. In Structure and Function of Major and Minor Small Nuclear Ribonucleoprotein Particles.
    24. (1987). Splicing of messenger RNA precursors.
    25. (1986). Structural and functional analysis of chicken U4 small nuclear RNA genes.
    26. (1990). Synthesis, conformation and hydrolytic stability of pl, p3-dinucleoside triphosphates related to mRNA 5'-cap, and comparative kinetic studies on their nucleoside and nucleoside monophosphate analogs.
    27. (1986). The conserved carboxyterminal cysteine of nuclear lamins is essential for lamin association with the nuclear envelope.
    28. (1984). The gapped duplex DNA approach to oligonucleotide directed mutation construction. Nucleic Acids Res.
    29. (1987). The role of small nuclear ribonucleoprotein particles in pre-mRNA splicing.
    30. (1990). The trimethylgnanosine cap structure of U1 snRNA is a component of a bipartite nuclear targeting signal.
    31. (1990). The U3 small nuclear ribonucleoprotein functions in the first step of preribosornal RNA processing.
    32. (1988). U snRNP assembly and transport.
    33. (1984). Xenopus laevis U1 snRNA genes. Characterization of transcriptionally active genes in major and minor repeated gene families.
    34. (1983). Xenopus laevis U2 snRNA genes: tandemly repeated transcription units sharing 5' and 3' flanking homology with other RNA polymerase H transcribed genes.
    35. (1987). Xenopus tropicalis U6 sn RNA genes transcribed by pol III contain the upstream promoter elements used by pol II dependent U snRNA genes. Nucleic Acids Res.

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