title: Adenine riboswitches and gene activation by disruption of a transcription terminator.
abstract: A class of riboswitches that recognizes guanine and discriminates against other purine analogs was recently identified. RNAs that carry the consensus sequence and structural features of guanine riboswitches are located in the 5' untranslated region (UTR) of numerous prokaryotic genes, where they control the expression of proteins involved in purine salvage and biosynthesis. We report that three representatives of this riboswitch class bind adenine with values for apparent dissociation constant (apparent K(d)) that are several orders of magnitude lower than those for binding guanine. Because preference for adenine is attributable to a single nucleotide substitution, the RNA most likely recognizes its ligand by forming a Watson-Crick base pair. In addition, the adenine riboswitch associated with the ydhL gene of Bacillus subtilis functions as a genetic 'on' switch, wherein adenine binding causes a structural rearrangement that precludes formation of an intrinsic transcription terminator stem.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, Connecticut 06520-8103, USA.
authors.forename: Maumita
authors.initials: M
authors.lastname: Mandal
authors.forename: Ronald R
authors.initials: RR
authors.lastname: Breaker
mesh_terms: D020121:5' Untranslated Regions; D000225:Adenine / Q000737:chemistry / Q000378:metabolism*; D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism; D020029:Base Pairing; D001483:Base Sequence; D019143:Evolution, Molecular; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D005812:Genes, Switch; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009690:Nucleic Acid Conformation; D012313:RNA / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013728:Terminator Regions, Genetic; D015533:Transcriptional Activation
chemical_list: D020121:5' Untranslated Regions; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012313:RNA; D000225:Adenine