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Molecular and Cellular Biology, October 2007, p. 7018-7027, Vol. 27, No. 20
0270-7306/07/$08.00+0     doi:10.1128/MCB.00516-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Involvement of Nuclear Import and Export Factors in U8 Box C/D snoRNP Biogenesis{triangledown}

Nicholas J. Watkins,1,2* Ira Lemm,2 and Reinhard Lührmann2

Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne, United Kingdom,1 Max Planck Institute for Biophysical Chemistry, Göttingen, Germany2

Received 25 March 2007/ Returned for modification 19 April 2007/ Accepted 9 August 2007

Box C/D snoRNPs, factors essential for ribosome biogenesis, are proposed to be assembled in the nucleoplasm before localizing to the nucleolus. However, recent work demonstrated the involvement of nuclear export factors in this process, suggesting that export may take place. Here we show that there are distinct distributions of U8 pre-snoRNAs and pre-snoRNP complexes in HeLa cell nuclear and cytoplasmic extracts. We observed differential association of nuclear export (PHAX, CRM1, and Ran) factors with complexes in the two extracts, consistent with nucleocytoplasmic transport. Furthermore, we show that the U8 pre-snoRNA in one of the cytoplasmic complexes contains an m3G cap and is associated with the nuclear import factor Snurportin1. Using RNA interference, we show that loss of either PHAX or Snurportin1 results in the incorrect localization of the U8 snoRNA. Our data therefore show that nuclear export and import factors are directly involved in U8 box C/D snoRNP biogenesis. The distinct distribution of U8 pre-snoRNP complexes between the two cellular compartments together with the association of both nuclear import and export factors with the precursor complex suggests that the mammalian U8 snoRNP is exported during biogenesis.

* Corresponding author. Mailing address: Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne NE2 4HH, United Kingdom. Phone: 44 191 222 6991. Fax: 44 191 222 6991. E-mail: n.j.watkins{at}ncl.ac.uk

{triangledown} Published ahead of print on 20 August 2007.

Molecular and Cellular Biology, October 2007, p. 7018-7027, Vol. 27, No. 20
0270-7306/07/$08.00+0     doi:10.1128/MCB.00516-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • McKeegan, K. S., Debieux, C. M., Watkins, N. J. (2009). Evidence that the AAA+ Proteins TIP48 and TIP49 Bridge Interactions between 15.5K and the Related NOP56 and NOP58 Proteins during Box C/D snoRNP Biogenesis. Mol. Cell. Biol. 29: 4971-4981 [Abstract] [Full Text]  


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