The amino- and carboxyl-terminal globular domains of type VI collagen are composed of several homologous modules similar to the type A collagen-binding modules present in von Willebrand factor. The human alpha 3(VI) chain that contributes most of the amino-terminal globule appears heterogeneous in size as a result of alternative splicing of two exons (Stokes D. G., Saitta, B., Timpl, R., and Chu, M.-L. (1991) J. Biol. Chem. 266, 8626-8633). In the present study, we report a further characterization of the 5'-end of the gene of the human alpha 3(VI) chain and show that transcription initiates at multiple sites. Southern blotting and DNA sequencing indicate that there is an additional type A exon (A9/N10) at about 1.8 kilobase pairs downstream of the exon coding for the signal peptide. The open reading frame of this additional exon reveals 1 cysteine and three potential N-glycosylation sites. Polymerase chain reaction, Northern blotting, and RNase protection assays demonstrate that exon A9/N10 is subject to alternative splicing in normal and tumor cell lines and that this generates more protein variants of the alpha 3(VI) chain than expected before. A comparison with the corresponding amino-terminal globule of the chicken alpha 3(VI) chain shows the presence of 1 additional cysteine in this portion of the molecule and suggests that human type VI collagen has more possibilities for structural and functional variations compared to chicken type VI collagen.

The human type VI collagen gene: mRNA and protein variants of the alpha3 chain generated by alternative splicing of an additional 5'-end exon.

BONALDO, PAOLO;
1992

Abstract

The amino- and carboxyl-terminal globular domains of type VI collagen are composed of several homologous modules similar to the type A collagen-binding modules present in von Willebrand factor. The human alpha 3(VI) chain that contributes most of the amino-terminal globule appears heterogeneous in size as a result of alternative splicing of two exons (Stokes D. G., Saitta, B., Timpl, R., and Chu, M.-L. (1991) J. Biol. Chem. 266, 8626-8633). In the present study, we report a further characterization of the 5'-end of the gene of the human alpha 3(VI) chain and show that transcription initiates at multiple sites. Southern blotting and DNA sequencing indicate that there is an additional type A exon (A9/N10) at about 1.8 kilobase pairs downstream of the exon coding for the signal peptide. The open reading frame of this additional exon reveals 1 cysteine and three potential N-glycosylation sites. Polymerase chain reaction, Northern blotting, and RNase protection assays demonstrate that exon A9/N10 is subject to alternative splicing in normal and tumor cell lines and that this generates more protein variants of the alpha 3(VI) chain than expected before. A comparison with the corresponding amino-terminal globule of the chicken alpha 3(VI) chain shows the presence of 1 additional cysteine in this portion of the molecule and suggests that human type VI collagen has more possibilities for structural and functional variations compared to chicken type VI collagen.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/125155
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