HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 281, Issue 27, 18691-18706, July 7, 2006

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 281/27/18691    most recent M602030200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted 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 Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Back, S. H. Articles by Kaufman, R. J. Search for Related Content PubMed PubMed Citation Articles by Back, S. H. Articles by Kaufman, R. J. Social Bookmarking                      What's this?

Cytoplasmic IRE1-mediated XBP1 mRNA Splicing in the Absence of Nuclear Processing and Endoplasmic Reticulum Stress^*

Sung Hoon Back, Kyungho Lee¹, Elizabeth Vink, and Randal J. Kaufman^¶2

From the Howard Hughes Medical Institute and Departments of Biological Chemistry and ^¶Internal Medicine, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0650

Accumulation of unfolded proteins in the endoplasmic reticulum (ER) activates an intracellular signal transduction program termed the unfolded protein response (UPR). In mammalian cells, the UPR is signaled in part through dimerization of ER membrane-localized IRE1 to activate its protein kinase and endoribonuclease activities. Activated IRE1 cleaves XBP1 mRNA at two sites to initiate an unconventional splicing reaction. The 5' and 3' fragments are subsequently joined by an RNA ligase activity, thereby removing a 26-base intron. This splicing reaction creates a translational frameshift to produce a functional XBP1 transcription factor. However, the cellular location and physiological processes required for splicing of XBP1 mRNA are not well characterized. To study these processes, XBP1 mRNAs were engineered in which translation of enhanced green fluorescence protein or luciferase required splicing of the XBP1 intron. Using cell lines that continuously or transiently express these reporter constructs, we show that cytoplasmic unspliced XBP1 mRNA is efficiently spliced by activated IRE1 and requires ongoing cellular transcription but not active translation. The XBP1 intron was effectively removed from RNA substrates transcribed from T7 RNA polymerase or delivered directly to the cytoplasm by RNA transfection, thus indicating that the splicing reaction does not require nuclear processing of the RNA substrate. Analysis of nuclear and cytoplasmic RNA fractions demonstrated that XBP1 mRNA splicing occurs in the cytoplasm. Moreover, an artificial F_v-IRE1N was engineered that was able to splice XBP1 mRNA upon chemical-induced dimerization. These findings demonstrate that IRE1 dimerization is sufficient to activate XBP1 mRNA splicing in the absence of the UPR. We propose that XBP1 mRNA cytoplasmic splicing provides a novel mechanism to rapidly induce translation of a transcription factor in response to a specific stimulus.

Received for publication, March 3, 2006 , and in revised form, April 26, 2006.

^* This work was supported by National Institutes of Health Grants HL052173 and DK42394 (to R. J. K.). 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 Fig. S1.

¹ Present address: Dept. of Biological Sciences, Konkuk University, Seoul 143-701, Korea.

² To whom correspondence should be addressed. Tel.: 734-763-9037; Fax: 734-763-9323; E-mail: kaufmanr{at}umich.edu.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				H. Bommiasamy, S. H. Back, P. Fagone, K. Lee, S. Meshinchi, E. Vink, R. Sriburi, M. Frank, S. Jackowski, R. J. Kaufman, et al. ATF6{alpha} induces XBP1-independent expansion of the endoplasmic reticulum J. Cell Sci., May 15, 2009; 122(10): 1626 - 1636. [Abstract] [Full Text] [PDF]

				E. Guerra, M. Trerotola, R. Dell' Arciprete, V. Bonasera, B. Palombo, T. El-Sewedy, T. Ciccimarra, C. Crescenzi, F. Lorenzini, C. Rossi, et al. A Bicistronic CYCLIN D1-TROP2 mRNA Chimera Demonstrates a Novel Oncogenic Mechanism in Human Cancer Cancer Res., October 1, 2008; 68(19): 8113 - 8121. [Abstract] [Full Text] [PDF]

				K. Hybiske, Z. Fu, C. Schwarzer, J. Tseng, J. Do, N. Huang, and T. E. Machen Effects of cystic fibrosis transmembrane conductance regulator and {Delta}F508CFTR on inflammatory response, ER stress, and Ca2+ of airway epithelia Am J Physiol Lung Cell Mol Physiol, November 1, 2007; 293(5): L1250 - L1260. [Abstract] [Full Text] [PDF]

				P. M. Bhende, S. J. Dickerson, X. Sun, W.-H. Feng, and S. C. Kenney X-Box-Binding Protein 1 Activates Lytic Epstein-Barr Virus Gene Expression in Combination with Protein Kinase D J. Virol., July 15, 2007; 81(14): 7363 - 7370. [Abstract] [Full Text] [PDF]

				E. Lai, T. Teodoro, and A. Volchuk Endoplasmic Reticulum Stress: Signaling the Unfolded Protein Response Physiology, June 1, 2007; 22(3): 193 - 201. [Abstract] [Full Text] [PDF]