Journal of Biological Chemistry
Volume 277, Issue 40, 4 October 2002, Pages 37804-37810
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MOLECULAR BASIS OF CELL AND DEVELOPMENTAL BIOLOGY
Identification of mRNA/Protein (mRNP) Complexes Containing Purα, mStaufen, Fragile X Protein, and Myosin Va and their Association with Rough Endoplasmic Reticulum Equipped with a Kinesin Motor*

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Purα, which is involved in diverse aspects of cellular functions, is strongly expressed in neuronal cytoplasm. Previously, we have reported that this protein controls BC1 RNA expression and its subsequent distribution within dendrites and that Purα is associated with polyribosomes. Here, we report that, following treatment with EDTA, Purα was released from polyribosomes in mRNA/protein complexes (mRNPs), which also contained mStaufen, Fragile X Mental Retardation Protein (FMRP), myosin Va, and other proteins with unknown functions. As the coimmunoprecipitation of these proteins by an anti-Purα antibody was abolished by RNase treatment, Purα may assist mRNP assembly in an RNA-dependent manner and be involved in targeting mRNPs to polyribosomes in cooperation with other RNA-binding proteins. The immunoprecipitation of mStaufen- and FMRP-containing mRNPs provided additional evidence that the anti-Purα detected structurally or functionally related mRNA subsets, which are distributed in the somatodendritic compartment. Furthermore, mRNPs appear to reside on rough endoplasmic reticulum equipped with a kinesin motor. Based on our present findings, we propose that this rough endoplasmic reticulum structure may form the molecular machinery that mediates and regulates multistep transport of polyribosomes along microtubules and actin filaments, as well as localized translation in the somatodendritic compartment.

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Published, JBC Papers in Press, July 29, 2002, DOI 10.1074/jbc.M203608200

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This work was supported by Grant 13680853 from the Ministry of Education, Culture, Sports, Science and Technology of Japan (to K. A.), by a Joint Research grant from Nihon University (to K. A.), and by a grant from the Ministry of Education, Culture, Sports, Science, and Technology of Japan to promote multidisciplinary research projects.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.