OriGene Sign up for PNAS Online eTocs
Link: Info for AuthorsLink: Editorial BoardLink: AboutLink: SubscribeLink: AdvertiseLink: ContactLink: Sitemap Link: PNAS Home
Proceedings of the National Academy of Sciences
Link: Current Issue "" Link: Archives "" Link: Online Submission ""  Link: Advanced Search

Published online on December 18, 2007, 10.1073/pnas.0705786105
PNAS | December 26, 2007 | vol. 104 | no. 52 | 20770-20775


This Article
Right arrow Figures Only
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Supporting Information
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a colleague
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My File Cabinet
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via CrossRef
Right arrow Citing Articles via ISI Web of Science (2)
Google Scholar
Right arrow Articles by Croft, M. T.
Right arrow Articles by Smith, A. G.
PubMed
Right arrow PubMed Citation
Right arrow Articles by Croft, M. T.
Right arrow Articles by Smith, A. G.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg  
What's this?

 Previous Article  | Table of Contents |  Next Article 

BIOLOGICAL SCIENCES / BIOCHEMISTRY
Thiamine biosynthesis in algae is regulated by riboswitches

Martin T. Croft, Michael Moulin, Michael E. Webb*, and Alison G. Smith{dagger}

Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, United Kingdom

Edited by Robert Haselkorn, University of Chicago, Chicago, IL, and approved November 7, 2007 (received for review June 20, 2007)

In bacteria, many genes involved in the biosynthesis of cofactors such as thiamine pyrophosphate (TPP) are regulated by ribo switches, regions in the 5' end of mRNAs to which the cofactor binds, thereby affecting translation and/or transcription. TPP riboswitches have now been identified in fungi, in which they alter mRNA splicing. Here, we show that addition of thiamine to cultures of the model green alga Chlamydomonas reinhardtii alters splicing of transcripts for the THI4 and THIC genes, encoding the first enzymes of the thiazole and pyrimidine branches of thiamine biosynthesis, respectively, concomitant with an increase in intracellular thiamine and TPP levels. Comparison with Volvox carteri, a related alga, revealed highly conserved regions within introns of these genes. Inspection of the sequences identified TPP riboswitch motifs, and RNA transcribed from the regions binds TPP in vitro. The THI4 riboswitch, but not the promoter region, was found to be necessary and sufficient for thiamine to repress expression of a luciferase-encoding reporter construct in vivo. The pyr1 mutant of C. reinhardtii, which is resistant to the thiamine analogue pyrithiamine, has a mutation in the THI4 riboswitch that prevents the THI4 gene from being repressed by TPP. By the use of these ribo switches, thiamine biosynthesis in C. reinhardtii can be effectively regulated at physiological concentrations of the vitamin.

regulation of metabolism | Chlamydomonas reinhardtii | luciferase reporter gene | alternative splicing of mRNA

Author contributions: M.T.C. and M.M. contributed equally to this work; M.T.C., M.M., M.E.W., and A.G.S. designed research; M.T.C., M.M., and M.E.W. performed research; M.M. contributed new reagents/analytic tools; M.T.C., M.M., M.E.W., and A.G.S. analyzed data; and M.T.C., M.M., M.E.W., and A.G.S. wrote the paper.

*Present address: School of Chemistry, University of Leeds, Leeds LS2 9JT, United Kingdom.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at www.pnas.org/cgi/content/full/0705786105/DC1.

{dagger}To whom correspondence should be addressed. E-mail: as25{at}cam.ac.uk

© 2007 by The National Academy of Sciences of the USA


Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg    What's this?


This article has been cited by other articles in HighWire Press-hosted journals:


Home page
 ScienceHome page
R. R. Breaker
Complex Riboswitches
Science, March 28, 2008; 319(5871): 1795 - 1797.
[Abstract] [Full Text] [PDF]