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| Subject Categories: Membranes & Transport | Proteins |
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| The EMBO Journal
(2003) 22, 1370–1380, doi:10.1093/emboj/cdg121 |
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| The path from nucleolar 90S to cytoplasmic 40S pre-ribosomes |
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Thorsten Schäfer1, Daniela Strau 1, Elisabeth Petfalski2, David Tollervey2 and Ed Hurt1
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1 BZH, Universität Heidelberg, Neuenheimer Feld 328, D-69120 Heidelberg, Germany 2 Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, UK To whom correspondence should be addressed Ed Hurt, cg5@ix.urz.uni-heidelberg.de Received 30 October 2002; Revised 9 January 2003; Accepted 16 January 2003. |
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| Abstract |
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Recent reports have increased our knowledge of the consecutive steps during 60S ribosome biogenesis substantially, but 40S subunit formation is less well understood. Here, we investigate the maturation of nucleolar 90S pre-ribosomes into cytoplasmic 40S pre-ribosomes. During the transition from 90S to 40S particles, the majority of non-ribosomal proteins ( 30 species) dissociate, and significantly fewer factors associate with 40S pre-ribosomes. Notably, some of these components are part of both early 90S and intermediate 40S pre-particles in the nucleolus (e.g. Enp1p, Dim1p and Rrp12p), whereas others (e.g. Rio2p and Nob1p) are found mainly on late cytoplasmic pre-40S subunits. Finally, temperature-sensitive mutants mapping either in earlier (enp1-1) or later (rio2-1) components exhibit defects in the formation and nuclear export of pre-40S subunits. Our data provide an initial biochemical map of the pre-40S ribosomal subunit on its path from the nucleolus to the cytoplasm. This pathway involves fewer changes in composition than seen during 60S biogenesis. |
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| Keywords: Enp1, nuclear export, ribosome biogenesis, ribosome export, 40S subunit |
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