title: Teleost introns are characterized by a high A+T content.
abstract: We previously observed that Antarctic fish genes contain intron sequences of high A+T content (60-70% average A+T) which are in stark contrast with adjacent protein coding-sequences. Here, we report that this disparity in intron/exon base composition is a common feature among teleosts. We analyzed 483 teleost genomic DNA sequences, containing 2583 introns, from 80 teleost genera that populate polar, temperate, or tropical habitats. Eighty-nine percent of teleost introns display an A+T content between 50-84% A+T with a mean of 60% A+T. In contrast, only 37% of teleost exons have an A+T content greater-than 50% with a mean of 48% A+T. A comparison to homologous mammalian genes showed a striking difference; in this case, introns and exons have similar base compositions, averaging 45-47% A+T. This indicates that most teleost genes exhibit a large difference in base composition between their introns and exons. There was no correlation of teleost intron A+T content to intron length or habitat temperature range. Thus, teleost intron sequences tend to show the common feature of being much higher in A+T content then neighboring exons.
authors.affiliation: Department of Biochemistry, Microbiology, and Molecular Biology, University of Maine, Orono, ME 04469-5735, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Winnard
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Sidell
authors.forename: Michael E
authors.initials: ME
authors.lastname: Vayda
mesh_terms: D000225:Adenine / Q000032:analysis; D000818:Animals; D000864:Antarctic Regions; D001482:Base Composition; D001483:Base Sequence; D005091:Exons; D005399:Fishes / Q000235:genetics*; D007438:Introns; D008322:Mammals / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D013696:Temperature; D013941:Thymine / Q000032:analysis
chemical_list: D000225:Adenine; D013941:Thymine