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J. Biol. Chem., Vol. 283, Issue 28, 19636-19645, July 11, 2008

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 283/28/19636    most recent M801014200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Heyd, F. Articles by Möröy, T. PubMed PubMed Citation Articles by Heyd, F. Articles by Möröy, T. Social Bookmarking                      What's this?

Differential Isoform Expression and Interaction with the P32 Regulatory Protein Controls the Subcellular Localization of the Splicing Factor U2AF26^*

Florian Heyd, Maria Carmo-Fonseca, and Tarik Möröy^¶1

From the Institut de Recherches Cliniques de Montréal and ^¶Department for Microbiology and Immunology, University of Montreal, Montréal, Quebec H2W 1R7, Canada and Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal

The U2 auxiliary factor (U2AF) is an integral part of the spliceosome that is important for the recognition of the 3' splice site. U2AF consists of a large and a small subunit, the prototypes of which are U2AF65 and U2AF35. Recent evidence suggests that several homologs of both U2AF subunits exist that are able to regulate alternative splicing. Here we have investigated the expression, intracellular localization, and nucleo-cytoplasmic shuttling of one homolog of the small U2AF subunit, U2AF26, and a splice variant lacking exon 7, U2AF26E7. In contrast to the nuclear U2AF26, which displays active nucleo-cytoplasmic shuttling, U2AF26E7 is localized in the cytoplasm. Our studies reveal a nuclear localization sequence in the C-terminal exons 7 and 8 of U2AF26 that differs from the known nuclear localization sequence in U2AF35. In addition, we could identify P32 as a protein that is able to interact with U2AF26 through this domain, and we demonstrate that this interaction is required for the nuclear translocation of U2AF26. Our results suggest the existence of two distinct nuclear import pathways for U2AF26 and U2AF35 that could independently control their intracellular distribution and availability to the splicing machinery. Such a mechanism could work in addition to the differential expression of U2AF homologs to contribute to the regulation of alternative splicing.

Received for publication, February 7, 2008 , and in revised form, May 5, 2008.

^* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Figs. 1-4.

¹ To whom correspondence should be addressed: Institut de Recherches Cliniques de Montréal, 110 Ave. des Pins Ouest, Montréal, Quebec H2W 1R7, Canada. Tel.: 514-987 5501; Fax: 514-987 5679; E-mail: Tarik.Moroy{at}ircm.qc.ca.

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