TPP riboswitch (THI element)

In molecular biology, the THI element is a highly conserved RNA secondary structure. It serves as a riboswitch [cite journal | last = Winkler | first = W | coauthors = Nahvi A, Breaker RR | year = 2002 | title = Thiamine derivatives bind messenger RNAs directly to regulate bacterial gene expression | journal = Nature | volume = 419 | pages = 952–956 | pmid = 12410317 | doi = 10.1038/nature01145] that binds directly to thiamine pyrophosphate (TPP) to regulate gene expression through a variety of mechanisms in archaea, bacteria and eukaryotes. [cite journal | last = Sudarsan | first = N | coauthors = Barrick JE, Breaker RR | year = 2003 | title = Metabolite-binding RNA domains are present in the genes of eukaryotes | journal = RNA | volume = 9 | pages = 644–647 | pmid = 12756322 | doi = 10.1261/rna.5090103] [cite journal | last = Kubodera | first = T | coauthors = Watanabe M, Yoshiuchi K, Yamashita N, Nishimura A, Nakai S, Gomi K, Hanamoto H | year = 2003 | title = Thiamine-regulated gene expression of Aspergillus oryzae thiA requires splicing of the intron containing a riboswitch-like domain in the 5'-UTR | journal = FEBS Lett | volume = 555 | pages = 516–520 | pmid = 14675766 | doi = 10.1016/S0014-5793(03)01335-8] TPP is the active form of thiamine (vitamin B₁), an essential coenzyme synthesised by coupling of pyrimidine and thiazole moieties in bacteria. The THI element is an extension of a previously detected thiamin-regulatory element, thi box. [cite journal | last = Rodionov | first = DA | coauthors = Vitreschak AG, Mironov AA, Gelfand MS | year = 2002 | title = Comparative genomics of thiamin biosynthesis in procaryotes. New genes and regulatory mechanisms | journal = J Biol Chem | volume = 277 | pages = 48949–48959 | pmid = 12376536 | doi = 10.1074/jbc.M208965200] Analysis of operon structures has identified a large number of new candidate thiamin-regulated genes, mostly transporters, in various prokaryotic organisms. [cite journal | last = Miranda-Rios | first = J | coauthors = Navarro M, Soberon M | year = 2001 | title = A conserved RNA structure (thi box) is involved in regulation of thiamin biosynthetic gene expression in bacteria | journal = Proc Natl Acad Sci U S A | volume = 98 | pages = 9736–9741 | pmid = 11470904 | doi = 10.1073/pnas.161168098] The x-ray crystal structure of the TPP riboswitch aptamer has been solved [cite journal | last = Serganov | first = A | coauthors = Polonskaia A, Phan AT, Breaker RR, Patel DJ | year = 2006 | title = Structural basis for gene regulation by a thiamine pyrophosphate-sensing riboswitch | journal = Nature. | volume = 441 | pages = 1167–1171 | pmid = 16728979 | doi = 10.1038/nature04740] .

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