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An early step in wobble uridine tRNA modification requires the Elongator complex
Umeå University, Faculty of Science and Technology, Molecular Biology (Faculty of Science and Technology). (Byström)
Umeå University, Faculty of Science and Technology, Molecular Biology (Faculty of Science and Technology). (Byström)
2005 (English)In: RNA: A publication of the RNA Society, ISSN 1355-8382, Vol. 11, no 4, 424-436 p.Article in journal (Refereed) Published
Abstract [en]

Elongator has been reported to be a histone acetyltransferase complex involved in elongation of RNA polymerase II transcription. In Saccharomyces cerevisiae, mutations in any of the six Elongator protein subunit (ELP1–ELP6) genes or the three killer toxin insensitivity (KTI11–KTI13) genes cause similar pleiotropic phenotypes. By analyzing modified nucleosides in individual tRNA species, we show that the ELP1–ELP6 and KTI11–KTI13 genes are all required for an early step in synthesis of 5-methoxycarbonylmethyl (mcm5) and 5-carbamoylmethyl (ncm5) groups present on uridines at the wobble position in tRNA. Transfer RNA immunoprecipitation experiments showed that the Elp1 and Elp3 proteins specifically coprecipitate a tRNA susceptible to formation of an mcm5 side chain, indicating a direct role of Elongator in tRNA modification. The presence of mcm5U, ncm5U, or derivatives thereof at the wobble position is required for accurate and efficient translation, suggesting that the phenotypes of elp1–elp6 and kti11–kti13 mutants could be caused by a translational defect. Accordingly, a deletion of any ELP1–ELP6 or KTI11KTI13 gene prevents an ochre suppressor tRNA that normally contains mcm5U from reading ochre stop codons.

Place, publisher, year, edition, pages
2005. Vol. 11, no 4, 424-436 p.
Keyword [en]
5-methoxycarbonylmethyl-2-thiouridine, 5-methoxycarbonylmethyluridine, 5-carbamoylmethyluridine, Elongator complex, KTI genes
URN: urn:nbn:se:umu:diva-2772DOI: 10.1261/rna.7247705PubMedID: 15769872OAI: diva2:141039
Available from: 2007-11-14 Created: 2007-11-14Bibliographically approved
In thesis
1. Formation and function of wobble uridine modifications in transfer RNA of Saccharomyces cerevisiae
Open this publication in new window or tab >>Formation and function of wobble uridine modifications in transfer RNA of Saccharomyces cerevisiae
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Transfer RNAs (tRNAs) act as adaptor molecules in decoding messenger RNA into protein. Frequently found in tRNAs are different modified nucleosides, which are derivatives of the four normal nucleosides, adenosine (A), guanosine (G), cytidine (C), and uridine (U). Although modified nucleosides are present at many positions in tRNAs, two positions in the anticodon region, position 34 (wobble position) and position 37, show the largest variety of modified nucleosides. In Saccharomyces cerevisiae, the xm5U type of modified uridines found at position 34 are 5-carbamoylmethyluridine (ncm5U), 5-carbamoylmethyl-2´-O-methyluridine, (ncm5Um), 5-methoxycarbonylmethyluridine (mcm5U), and 5-methoxycarbonyl-methyl-2-thiouridine (mcm5s2U). Based on the complex structure of these nucleosides, it is likely that their formation requires several synthesis steps.

The Elongator complex consisting of proteins Elp1p - Elp6p, and the proteins Kti11p - Kti14p, Sit4p, Sap185p, and Sap190p were shown to be involved in 5-carbamoylmethyl (ncm5) and 5-methoxycarbonylmethyl (mcm5) side-chain synthesis at position 34 in eleven tRNA species. The proteins Urm1p, Uba4p, Ncs2p, Ncs6p, and Yor251cp were also identified to be required for the 2-thio (s2) group formation of the modified nucleoside mcm5s2U at wobble position.

Modified nucleosides in the anticodon region of tRNA influence the efficiency and fidelity of translation. The identification of mutants lacking ncm5-, mcm5-, or s2-group at the wobble position allowed the investigation of the in vivo role of these nucleosides in the tRNA decoding process. It was revealed that the presence of ncm5-, mcm5- or s2-group promotes reading of G-ending codons. The concurrent presence of the mcm5- and the s2-groups in the wobble nucleoside mcm5s2U improves reading of A- and G-ending codons, whereas absence of both groups is lethal to the yeast cell.

The Elongator complex was previously proposed to regulate polarized exocytosis and to participate in elongation of RNA polymerase II transcription. The pleiotropic phenotypes observed in Elongator mutants were therefore suggested to be caused by defects in exocytosis and transcription of many genes. Here it is shown that elevated levels of hypomodified tRNALys [mcm5s2UUU] and tRNAGln[mcm5s2UUG] can efficiently suppress these pleiotropic phenotypes, suggesting that the defects in transcription and exocytosis are indirectly caused by inefficient translation of mRNAs encoding proteins important in these processes.

Place, publisher, year, edition, pages
Umeå: Molekylärbiologi (Teknisk-naturvetenskaplig fakultet), 2007. 44 p.
Transfer RNA, Modified nucleoside, Elongator complex, Wobble uridine, Decoding
National Category
Biochemistry and Molecular Biology
urn:nbn:se:umu:diva-1433 (URN)978-91-7264-450-2 (ISBN)
Public defence
2007-12-12, Major Groove, Byggnad 6L, Dept. of Molecular Biology, Umeå University, Umeå, 10:00 (English)
Available from: 2007-11-14 Created: 2007-11-14 Last updated: 2009-10-22Bibliographically approved

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