The human type VI collagen gene. mRNA and protein variants of the alpha 3 chain generated by alternative splicing of an additional 5-end exon.
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.
Zanussi
S
S
Divisione di Oncologia Sperimentale 2, Centro di Riferimento Oncologico, Aviano, Italy.
Doliana
R
R
Segat
D
D
Bonaldo
P
P
Colombatti
A
A
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D002645:Chickens; D003094:Collagen / Q000032:analysis / Q000235:genetics*; D004273:DNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D005091:Exons; D005455:Fluorescent Antibody Technique; D005796:Genes; D014644:Genetic Variation; D015698:Genomic Library; D005910:Glioma; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000032:analysis; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D001616:beta-Galactosidase / Q000032:analysis / Q000235:genetics
D004273:DNA, Neoplasm; D046911:Macromolecular Substances; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D003094:Collagen; D001616:beta-Galactosidase