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Analysis of the secondary structure of expansion segment 39 in ribosomes from fungi, plants and mammals
Södertörn University, School of Life Sciences.
Södertörn University, School of Life Sciences. Stockholm University.
Södertörn University, School of Life Sciences. Stockhom University.
2006 (English)In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 357, no 3, 904-916 p.Article in journal (Refereed) Published
Abstract [en]

The structure of expansion segment 39, E539, in eukaryotic 23 S-like ribosomal RNA was analysed using a combination of chemical and enzymic reagents. Ribosomes were isolated from yeast, wheat, mouse, rat and rabbit, five organisms representing three different eukaryotic kingdoms. The isolated ribosomes were treated with structure-sensitive chemical and enzymic reagents and the modification patterns analysed by primer extension and gel electrophoresis on an ABI 377 automated DNA sequencer. The expansion segment was relatively accessible to modification by both enzymic and chemical probes, suggesting that ES39 was exposed on the surface of the ribosomes. The collected modification data were used in secondary structure modelling of the expansion segment. Despite considerable variation in both sequence and length between organisms from different kingdoms, the structure analysis of the expansion segment gave rise to structural fingerprints that allowed identification of homologous structures in ES39 from fungi, plants and mammals. The homologous structures formed an initial helix and an invariant hairpin connected to the initial helix via a long single-stranded loop. The remaining part of the ES39 sequences accounted for most of the length variation seen between the analysed species. This part could form additional, albeit less similar, hairpins. A comparison of ES39 sequences from other fungi, plants and mammals showed that identical structures could be formed in these organisms.

Place, publisher, year, edition, pages
2006. Vol. 357, no 3, 904-916 p.
National Category
Biochemistry and Molecular Biology
URN: urn:nbn:se:sh:diva-14303DOI: 10.1016/j.jmb.2006.01.043ISI: 000236629300019PubMedID: 16473366ScopusID: 2-s2.0-33644955476OAI: diva2:468136
Available from: 2011-12-20 Created: 2011-12-20 Last updated: 2017-02-13Bibliographically approved
In thesis
1. Ribosome and ribosomal RNA Structure: An experimental and computational analysis of expansion segments in eukaryotic ribosomal RNA
Open this publication in new window or tab >>Ribosome and ribosomal RNA Structure: An experimental and computational analysis of expansion segments in eukaryotic ribosomal RNA
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ribosomes are large ribonucleoprotein complexes which incorporate amino acids into peptide chains during translational process in all types of living cells. The eukaryotic ribosome is larger compared to its prokaryotic counterpart. The size differences are due to a larger protein part and that the rRNA contains eukaryote specific expansion segments (ES). Cryo-EM reconstruction has visualized many ES on the ribosomal surface which have given clues about function and structural features. However, the secondary structures of most ES are unknown or ill defined. In this thesis, the secondary and also to a certain extent the tertiary structures of several ES are determined by using computational methods and biochemical experimental techniques. The juxtaposition of ES6 close to ES3 in the Cryo-EM image of the yeast ribosome suggested that ES3 and ES6 might interact. A computational analysis of more than 2900 sequences shows that a complementary helical region of seven to nine contiguous base pairs can form between ES3 and ES6 in almost all analyzed sequences. Biochemical in situ experiments support the proposed interaction. Secondary structure models are presented for ES3 and ES6 in 18S rRNA and ES39 in 28S rRNA, where homologous structural elements could be modeled in the experimentally analyzed ribosomes from fungi, plants and mammals. The structure models were further supported by computational methods where the ES6 structure and the ES39 structure could be formed in more than 6000 and 900 sequences respectively. A tertiary structure model of ES3 and ES6 including the helical interaction is presented. An in vitro transcribed and folded ES6 sequence differed from that observed in situ, suggesting that chaperones, ribosomal proteins, and/or the tertiary rRNA interaction could be involved in the in vivo folding of ES6. An analysis of the similarities between ES39 structures suggests that it might be under selective constraint to preserve its secondary structure.

Place, publisher, year, edition, pages
Stockholm: Wenner-Gren Institute for Experimental Biology, Stockholm university, 2008. 72 p.
eukaryotes, expansion segment, ribosomes, rRNA, secondary structure, structure of rRNA.
National Category
Cell and Molecular Biology
urn:nbn:se:sh:diva-32043 (URN)978-91-7155-603-5 (ISBN)
Public defence
2008-05-23, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 13:00 (English)
Available from: 2017-02-13 Created: 2017-02-13 Last updated: 2017-02-13Bibliographically approved

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Nygård, OddAlkemar, GunnarLarsson, Sofia L
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