title: Descent of a split RNA.
abstract: tmRNA is found in the usual one-piece form in most cyanobacteria, but a small clade has an unusual two-piece form, resulting from processing of a circularly permuted precursor RNA. Here, the secondary structure of the cyanobacterial one-piece tmRNA is established by phylogenetic sequence comparison; it deviates from most tmRNAs in having an extra (fifth) pseudoknot and a branched structure at the end of the tag reading frame. Patterns of sequence conservation between the two cyanobacterial tmRNA types suggest particular events in the evolution of the two-piece form. A simple gene permutation model of tandem duplication followed by loss of the outermost segments appears inadequate. An additional rearrangement is proposed, in which a structure impaired by deletion was regenerated at the expense of a neighboring structure.
authors.affiliation: Department of Biology, Indiana University, 1001 East Third Street, Bloomington, IN 47405, USA. kellwill@indiana.edu
authors.forename: Kelly P
authors.initials: KP
authors.lastname: Williams
mesh_terms: D001483:Base Sequence; D000458:Cyanobacteria / Q000235:genetics*; D019143:Evolution, Molecular; D020440:Gene Duplication; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010802:Phylogeny; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics*; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid
chemical_list: D012329:RNA, Bacterial; C096222:tmRNA