PreQ1 riboswitch

The PreQ1-I riboswitch is a cis-acting element identified in bacteria which regulates expression of genes involved in biosynthesis of the nucleoside queuosine from GTPcite journal | author = Roth A, Winkler WC, Regulski EE, Lee BW, Lim J, Jona I, Barrick JE, Ritwik A, Kim JN, Welz R, Iwata-Reuyl D, Breaker RR | title = A riboswitch selective for the queuosine precursor preQ1 contains an unusually small aptamer domain | journal = Nat Struct Mol Biol | volume = 14 | issue = 4 | pages = 308–17 | year = 2007 | pmid = 17384645 | doi = 10.1038/nsmb1224 | issn = ] . This RNA element known as a riboswitch binds preQ₁ (pre-queuosine₁), an intemediate in the queuosine pathway. Riboswitch function has been characterised in the bacterium "Bacillus subtilis", where the riboswitch is located in the leader of the ykvJKLM (queCDEF) operon which encodes four genes necessary for queuosine production cite journal | author = Reader JS, Metzgar D, Schimmel P, de Crécy-Lagard V | title = Identification of four genes necessary for biosynthesis of the modified nucleoside queuosine | journal = J. Biol. Chem. | volume = 279 | issue = 8 | pages = 6280–5 | year = 2004 | pmid = 14660578 | doi = 10.1074/jbc.M310858200 | issn = ] . In this organism, PreQ₁ binding to the riboswitch aptamer is thought to induce premature transcription termination within the leader to down-regulate expression of these genes. The preQ₁ riboswitch is distinguished by its unusually small aptamer, compared to other riboswitches. PreQ1-II riboswitches also bind preQ₁, but have an unrelated, distinct structure.

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