CHROMOSOMAL LOCALIZATION OF A HUMAN MUCIN GENE (MUC8) AND CLONING OF THE CDNA CORRESPONDING TO THE CARBOXY-TERMINUS

A partial cDNA (pAM1) encoding a major airway mucin glycoprotein with novel tandem repetitive sequence has recently been cloned (Shankar, V. , M. S. Gilmore, R. C. Elkins, and G. P. Sachdev. 1994. Biochem. J. 30 0:295-298). In this article, we report additional new sequence derived by 3'-rapid amplification of cDNA ends technique. The sequence corres ponds to a stop codon, 3'-untranslated region of 458 bp, a polyadenyla tion signal, and poly A(+) tail, and represents the extreme carboxy te rminus of MUC8. A plasmid construct (pAM3) in pBluescript was generate d by in-frame ligation of pAM1 to the 479-bp 3'UTR of MUC8. A 5'-end 3 25-bp fragment of this cDNA subcloned into the protein fusion and expr ession vector pET28b(+) was used to generate fusion protein under the control of T7 promoter. The purified fusion protein as well as synthet ic peptide corresponding to the MUC8 repeat sequence (TSCPRPLQEGTPGS) were used to raise polyclonal antibodies in rabbits. The antiserum to the fusion protein and to the synthetic peptide reacted with the degly cosylated major tracheobronchial mucin. Immunohistochemical studies us ing the above antibodies localized the MUC8 protein product to submuco sal glands in human tracheal epithelium. Furthermore, the gene from wh ich this cDNA is derived, was mapped to chromosome 12 using DNA from a panel of human-mouse somatic cell hybrids. Fluorescence in situ hybri dization was used to assign the regional localization to 12q24.3. Sinc e the eight known human mucin genes map to other chromosomes, we have named this gene MUC8 in accordance with mucin gene nomenclature.