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Immunochemical identification of novel high‐molecular‐weight protein isoforms of the adenomatous polyposis coli (APC) gene
Author(s) -
Kraus Cornelia,
ReinaSanchez Julio,
S˘uleková Zora,
Ballhausen Wolfgang G.
Publication year - 1996
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/(sici)1097-0215(19960126)65:3<383::aid-ijc18>3.0.co;2-b
Subject(s) - exon , epitope , microbiology and biotechnology , monoclonal antibody , gene isoform , adenomatous polyposis coli , biology , gene , peptide sequence , gene product , antibody , biochemistry , genetics , gene expression , cancer , colorectal cancer
Mapping analyses of monoclonal antibodies (MAbs) directed against the amino‐terminus of the adenomatous polyposis coli (APC) gene product revealed that epitopes recognized by the MAbs FE9, CF11 and AC4 constitute different peptide sequences encoded by the APC exons 1, 2 and 3, respectively. The protein pattern detected with these specificity‐defined immunoreagents, however, differed depending on the particular antibody used on Western blots of cellular urea extracts. APC exon 15‐positive “classic” p300 apc polypeptide chains were identified by the MAb FE9, MAb CF11 and the C‐terminus‐specific MAb IEI, but only weak signals were obtained with the AC4 MAb, which defines an exon 3‐encoded epitope. In contrast with this immunoreactivity, 2 novel high m.w. products of approx. 150/160 and 200 kDa were exclusively recognized by the AC4 MAb, which was shown to bind to the APC exon 3‐encoded peptide sequence SRESTGYL. A molecular form of some 400 kDa was identified to represent a disulfide‐bound oligomer of the p150/160 apc molecules. The novel APC‐related molecules did not contain exon 1‐ and exon 15‐encoded epitopes, as confirmed with the help of the FE9 and IE1 MAbs, respectively. This observation was corroborated by the fact that these novel proteins were not truncated in a collection of familial adenomatous polyposis patients with stop mutations in exon 15. We conclude, that APC MAb AC4‐reactive p150/160 and p200 polypeptide chains represent novel genuine products of the APC gene devoid of exon 1‐ and exon 15‐encoded protein interaction domains. © 1996 Wiley‐Liss, Inc.