title: Multiple gains of spliceosomal introns in a superfamily of vertebrate protease inhibitor genes.
abstract: BACKGROUND
  Intron gains reportedly are very rare during evolution of vertebrates, and the mechanisms underlying their creation are largely unknown. Previous investigations have shown that, during metazoan radiation, the exon-intron patterns of serpin superfamily genes were subject to massive changes, in contrast to many other genes.
  
  
  RESULTS
  Here we investigated intron dynamics in the serpin superfamily in lineages pre- and postdating the split of vertebrates. Multiple intron gains were detected in a group of ray-finned fishes, once the canonical groups of vertebrate serpins had been established. In two genes, co-occurrence of non-standard introns was observed, implying that intron gains in vertebrates may even happen concomitantly or in a rapidly consecutive manner. DNA breakage/repair processes associated with genome compaction are introduced as a novel factor potentially favoring intron gain, since all non-canonical introns were found in a lineage of ray-finned fishes that experienced genomic downsizing.
  
  
  CONCLUSIONS
  Multiple intron acquisitions were identified in serpin genes of a lineage of ray-finned fishes, but not in any other vertebrates, suggesting that insertion rates for introns may be episodically increased. The co-occurrence of non-standard introns within the same gene discloses the possibility that introns may be gained simultaneously. The sequences flanking the intron insertion points correspond to the proto-splice site consensus sequence MAG upward arrowN, previously proposed to serve as intron insertion site. The association of intron gains in the serpin superfamily with a group of fishes that underwent genome compaction may indicate that DNA breakage/repair processes might foster intron birth.
authors.affiliation: Department of Biotechnology, Faculty of Technology and Center for Biotechnology, University of Bielefeld, D-33501 Bielefeld, Germany. hr@zellkult.techfak.uni-bielefeld.de
authors.forename: Hermann
authors.initials: H
authors.lastname: Ragg
authors.forename: Abhishek
authors.initials: A
authors.lastname: Kumar
authors.forename: Katharina
authors.initials: K
authors.lastname: Köster
authors.forename: Caterina
authors.initials: C
authors.lastname: Bentele
authors.forename: Yunjie
authors.initials: Y
authors.lastname: Wang
authors.forename: Marc-André
authors.initials: MA
authors.lastname: Frese
authors.forename: Natalie
authors.initials: N
authors.lastname: Prib
authors.forename: Olaf
authors.initials: O
authors.lastname: Krüger
mesh_terms: D000595:Amino Acid Sequence; D000808:Angiotensinogen / Q000235:genetics; D000818:Animals; D005399:Fishes / Q000235:genetics; D007438:Introns; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D015843:Serpins / Q000235:genetics*; D017381:Spliceosomes / Q000235:genetics*; D014714:Vertebrates / Q000235:genetics
chemical_list: D015843:Serpins; D000808:Angiotensinogen
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