The structure and organization of lamprin genes: multiple-copy genes with alternative splicing and convergent evolution with insect structural proteins.
Lamprin is a unique structural protein which forms the extracellular matrix of several cartilaginous structures found in the lamprey. Lamprin is noncollagenous in nature but shows sequence similarities to elastins and to insect structural proteins. Here, we characterize the structure and organization of lamprin genes, demonstrating the presence of multiple similar but not identical copies of the lamprin gene in the genome of the lamprey. In at least one species of lamprey, Lampetra richardsoni, the multiple gene copies are arranged in tandem in the genome in a head-to-tail orientation. Lamprin genes from Petromyzon marinus contain either seven or eight exons, with exon 4 being alternatively spliced in all genes, resulting in a total of six different lamprin transcripts. All exon junctions are of class 1,1. An unusual feature of the lamprin gene structure is the distribution of the 3' untranslated region sequence among multiple exons. A TATA box and cap sequence have been identified in upstream sequences in close proximity to the transcription start site, but no CAAT box could be identified. Sequence and gene structure comparisons between lamprins, elastins, and insect structural proteins suggest that the regions of sequence similarity are the result of a process of convergent evolution.
Robson
P
P
Division of Cardiovascular Research, Hospital for Sick Children and Department of Biochemistry, University of Toronto, Toronto, Canada.
Wright
G M
GM
Youson
J H
JH
Keeley
F W
FW
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D005091:Exons; D016326:Extracellular Matrix Proteins / Q000235:genetics*; D018628:Gene Dosage; D005796:Genes / Q000235:genetics*; D014644:Genetic Variation; D019476:Insect Proteins / Q000235:genetics; D007438:Introns; D007798:Lampreys / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
D016326:Extracellular Matrix Proteins; D019476:Insect Proteins; C101583:lamprin; D004247:DNA