title: Identification of three annexin IX isoforms generated by alternative splicing of the carboxyl-terminal exon in silkworm, Bombyx mori.
abstract: Annexins (ANXs) are a family of structurally related proteins with Ca(2+)-dependent phospholipid-binding properties. Here we report the cloning of three cDNAs each encoding annexin IX (ANX IX) isoforms from unfertilized eggs of the silkworm, Bombyx mori. The analysis of exon/intron structures showed that the three mRNAs, named ANX IX-A (2300bp), ANX IX-B (1884bp) and ANX IX-C (1409bp), respectively, were generated from a single gene by alternative usage of a 3'-splice site of the last exon. Thus the three isoforms have an identical sequence from amino acid residues 1 to 307 and this region shows approximately 77% identity to Drosophila melanogaster ANX IX. Only amino acid residues 308-324 (A) or 308-323 (B and C), which correspond to the C-terminal tail, are different in the three proteins. A RT-PCR analysis indicated that the three isoforms of silkworm ANX IX were specifically expressed in various larval tissues and development stages. Interestingly, the C-terminal tail in ANXs I, II and V were previously confirmed as a binding region for protein kinase C. Thus generation of the three ANX IX isoforms in the silkworm, that are different from other ANXs, may have a functional significance other than binding to Ca(2+).
authors.affiliation: Institute of Genetic Resources, Faculty of Agriculture, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, 812-8581, Fukuoka, Japan.
authors.forename: Q Y
authors.initials: QY
authors.lastname: Xia
authors.forename: H
authors.initials: H
authors.lastname: Fujii
authors.forename: T
authors.initials: T
authors.lastname: Kusakabe
authors.forename: Y
authors.initials: Y
authors.lastname: Banno
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D017302:Annexins / Q000235:genetics*; D001483:Base Sequence; D012831:Bombyx / Q000235:genetics*; D003001:Cloning, Molecular / Q000379:methods; D018076:DNA, Complementary; D004331:Drosophila melanogaster / Q000235:genetics; D005091:Exons; D015870:Gene Expression; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000235:genetics; D022821:RNA Splice Sites; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D017302:Annexins; D018076:DNA, Complementary; D020033:Protein Isoforms; D022821:RNA Splice Sites