Among the nuclear proteins associated with mRNAs before their export to the cytoplasm are the abundant heterogeneous nuclear (hn) RNPs. Several of these contain the M9 signal that, in the case of hnRNP A1, has been shown to be sufficient to signal both nuclear export and nuclear import in cultured somatic cells. Kinetic competition experiments are used here to demonstrate that M9-directed nuclear import in Xenopus oocytes is a saturable process. Saturating levels of M9 have, however, no effect on the import of either U snRNPs or proteins carrying a classical basic NLS. Previous work demonstrated the existence of nuclear export factors specific for particular classes of RNA. Injection of hnRNP A1 but not of a mutant protein lacking the M9 domain inhibited export of mRNA but not of other classes of RNA. This suggests that hnRNP A1 or other proteins containing an M9 domain play a role in mRNA export from the nucleus. However, the requirement for M9 function in mRNA export is not identical to that in hnRNP A1 protein transport.
A Role for the M9 Transport Signal of hnRNP A1 in mRNA Nuclear Export
1.Abbreviations used in this paper: CBC, cap binding complex; hn, heterogenous nuclear; IBB, importin β binding; m3G, methyl2,2,7guanosine; NES, nuclear export signal; NLS, nuclear localization signal; NPLc, nucleoplasmin core domain; U sn, uracil rich small nuclear.
E. Izaurralde and U. Fischer were recipients of fellowships from the Human Frontier Science Program Organization and the Deutsches Krebsforschungszentrum (AIDS-Stipendienprogramm), respectively. A. Jarmolowski was supported by the Polish Research Committee (grant KBN 6P04A03511). G. Dreyfuss is an investigator of the Howard Hughes Medical Institute.
Please address all correspondence to Iain Mattaj, European Molecular Biology Laboratory, D-69117 Heidelberg, Germany. Tel.: 49-6221-387-393; Fax: 49-6221-387-518; E-mail: [email protected]
Elisa Izaurralde's present address is University of Geneva, Department of Molecular Biology, 30 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland.
Artur Jarmolowski's present address is Institute of Molecular Biology and Biotechnology, Department of Biopolymer Biochemistry, 60371 Poznan, Poland.
Elisa Izaurralde, Artur Jarmolowski, Christina Beisel, Iain W. Mattaj, Gideon Dreyfuss, Utz Fischer; A Role for the M9 Transport Signal of hnRNP A1 in mRNA Nuclear Export. J Cell Biol 7 April 1997; 137 (1): 27–35. doi: https://doi.org/10.1083/jcb.137.1.27
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