title: Eukaryotic evolution: early origin of canonical introns.
abstract: Spliceosomal introns, one of the hallmarks of eukaryotic genomes, were thought to have originated late in evolution and were assumed not to exist in eukaryotes that diverged early -- until the discovery of a single intron with an aberrant splice boundary in the primitive 'protozoan' Giardia. Here we describe introns from a close relative of Giardia, Carpediemonas membranifera, that have boundary sequences of the normal eukaryotic type, indicating that canonical introns are likely to have arisen very early in eukaryotic evolution.
authors.affiliation: Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada. simpson@hades.biochem.da.ca
authors.forename: Alastair G B
authors.initials: AG
authors.lastname: Simpson
authors.forename: Erin K
authors.initials: EK
authors.lastname: MacQuarrie
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Roger
mesh_terms: D000818:Animals; D001483:Base Sequence; D005057:Eukaryotic Cells / Q000145:classification* / Q000378:metabolism*; D019143:Evolution, Molecular; D005872:Giardia / Q000235:genetics; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D007438:Introns / Q000235:genetics*; D017851:Phosphotransferases (Carboxyl Group Acceptor) / Q000235:genetics*; D010802:Phylogeny; D022821:RNA Splice Sites / Q000235:genetics; D012326:RNA Splicing / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018840:HSP70 Heat-Shock Proteins; D022821:RNA Splice Sites; D012333:RNA, Messenger; D017851:Phosphotransferases (Carboxyl Group Acceptor); C019288:carbamate kinase