Human {beta}2 chain of laminin (formerly S chain): cDNA cloning, chromosomal localization, and expression in carcinomas
- Univ. Institute of Pathological Anatomy, Copenhagen (Denmark); and others
Overlapping cDNA clones that encode the full-length human laminin {beta}2 chain, formerly called the S chain, were isolated. The cDNA of 5680 nt contains a 5391-nt open reading frame encoding 1797 amino acids. At the amino terminus is a 32-amino-acid signal peptide that is followed by the mature {beta}2 chain polypeptide of 1765 amino acids with a calculated molecular mass of 192,389 Da. The human {beta}2 chain is predicted to have all of the seven structural domains typical of the {beta} chains of laminin, including the short cysteine-rich {alpha} region. The amino acid sequence of human {beta}2 chain showed 86.1% sequence identity to the rat {beta}2 chain, 50.0% to human {beta}1 chain, and 36.3% to the human {beta}3 chain. The greatest sequence identity was in domains VI, V, and III. The sequence of a 24-amino-acid peptide fragment isolated from the {beta}2 chain of laminin purified from human amniotic basement membrane matched the sequence predicted from the cDNA, confirming that the cDNA encodes human {beta}2 laminin. The cDNA was used to assign the gene (LAMB2) to human chromosome 3p21 by in situ hybridization. It is not linked to genes for human laminin chains {alpha}1, {beta}1, and {gamma}1 or other known laminin genes. Immunostaining showed that the {beta}2 chain is localized to the smooth muscle basement membranes of the arteries, while the homologous {beta}1 chain is confined to the subendothelial basement membranes. The {beta}2 chain was found in the basement membranes of ovarian carcinomas but not colon carcinomas. These results indicate that the expression of the {beta}2 chain gene is tightly regulated in normal human tissues and in disease. 43 refs., 6 figs., 1 tab.
- OSTI ID:
- 250256
- Journal Information:
- Genomics, Vol. 24, Issue 2; Other Information: PBD: 15 Nov 1994
- Country of Publication:
- United States
- Language:
- English
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