title: Cytokeratin expression in simple epithelia. III. Detection of mRNAs encoding human cytokeratins nos. 8 and 18 in normal and tumor cells by hybridization with cDNA sequences in vitro and in situ.
abstract: We describe cDNA clones of mRNAs encoding human cytokeratins nos. 8 and 18, and the amino acid sequences deduced from their nucleotide sequences. Human cytokeratin no. 8 is a typical cytokeratin of the basic (type II) subfamily, which is highly homologous to the corresponding bovine and amphibian (Xenopus laevis) proteins; however, unlike the amphibian protein, it does not contain glycine-rich oligopeptide repeats in its carboxyterminal 'tail' domain. Comparison with the reported amino acid sequences of two fragments of human 'tissue polypeptide antigen' (TPA), a widely used serodiagnostic carcinoma marker, revealed sequence identity, indicating that this serum component is derived from the intracellular cytokeratin no. 8 present in diverse kinds of epithelia and epithelium-derived tumors. Human cytokeratin no. 18 is very similar to the corresponding murine protein but contains two additional blocks of 4 and 5 amino acids in the 'head' portion. These cDNA clones and the RNA probes derived therefrom were used to detect specifically mRNAs by Northern-blot assays of RNAs from various carcinomas and cultured carcinoma cells. Using in situ hybridization on frozen sections of tumor-containing tissues, notably lymph nodes containing metastatic breast carcinoma, we were able to demonstrate the specificity and sensitivity of this procedure. The potential value for cell-biological research and pathology of being able to detect a mRNA encoding a given cytokeratin polypeptide in situ is discussed.
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002294:Carcinoma, Squamous Cell; D002460:Cell Line; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D005260:Female; D006801:Humans; D007633:Keratins / Q000235:genetics*; D009693:Nucleic Acid Hybridization; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics*; D014158:Transcription, Genetic; D014846:Vulvar Neoplasms
chemical_list: D012333:RNA, Messenger; D007633:Keratins; D004247:DNA