A new alternative transcript encodes a 60 kDa truncated form of integrin beta 3.
A cDNA for integrin beta 3 isolated from a human erythroleukaemia (HEL) cell library contained a 340 bp insert at position 1281. This mRNA, termed beta 3c, results from the use of a cryptic AG donor splice site in intron 8 of the beta 3 gene, and is different from a previously described alternative beta 3 mRNA. The predicted open reading frame of beta 3C stops at a TAG stop codon 69 bp downstream from position 1281. It starts with the signal peptide and the 404 N-terminal extracellular residues of beta 3, encompassing the ligand binding sites, followed by 23 C-terminal intron-derived residues, corresponding to a truncated form of beta 3 lacking the cysteine-rich, transmembrane and cytoplasmic domains. Expression of beta 3C mRNA was demonstrated in human platelets, megakaryocytes, endothelial cells and HEL cells by reverse transcriptase/PCR. The beta 3C transcript was also demonstrated in the mouse, suggesting its conservation through evolution. Finally, a 60 kDa polypeptide corresponding to the beta 3C alternative transcript was demonstrated in platelets by Western blotting using a polyclonal antibody raised against a synthetic peptide designed from the beta 3C intronic sequence. Taken together, these results suggest a biological role for beta 3C, the first alternative transcript showing an altered extracellular domain of a beta integrin.
Djaffar
I
I
Unité 348 INSERM, Hôpital Lariboisière, Paris, France.
Chen
Y P
YP
Creminon
C
C
Maclouf
J
J
Cieutat
A M
AM
Gayet
O
O
Rosa
J P
JP
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001792:Blood Platelets / Q000378:metabolism; D018076:DNA, Complementary; D006801:Humans; D039661:Integrin beta3; D016023:Integrins / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics*; D014407:Tumor Cells, Cultured
D018076:DNA, Complementary; D039661:Integrin beta3; D016023:Integrins; D012333:RNA, Messenger