EXPRESSION OF MUC1 MUCIN GENE BY HAMSTER TRACHEAL SURFACE EPITHELIAL-CELLS IN PRIMARY CULTURE

Primary hamster tracheal surface epithelial (HTSE) cells carry mucin-l ike glycoproteins on the apical surface which are releasable by neutro phil elastase. In some cancer cells, mucins are localized on the cell surface and have been shown to be encoded by the MUC1 mucin gene. The objectives of the present experiments were: (1) to determine if HTSE c ells express MUC1 mucin gene; (2) if they do, to isolate and character ize the hamster MUC1 complementary DNA (cDNA); and (3) to examine the pattern of MUC1 mRNA expression at different stages of culture. Revers e transcriptase-polymerase chain reaction amplification of HTSE cell R NAs using degenerate primers based on homologous sequences between the human and mouse MUC1 genes revealed the presence of a cDNA (0.5 kb) w hich has an 88 % similarity in sequence with the mouse MUC1 cDNA. Usin g this 0.5 kb cDNA as a probe, an HTSE cell cDNA library was screened to isolate a hamster MUC1 cDNA clone. Sequence analysis of the cDNA re vealed that it encodes an integral membrane protein of 676 amino acids which consists of (1) an N-terminal signal sequence, (2) the tandem r epeat domain encoding 12 repeats of 20 amino acids, and (3) the C-term inal region consisting of degenerate tandem repeats and a unique seque nce containing both the transmembrane and cytoplasmic domains. The pre sence of seven tyrosine residues in the cytoplasmic domain suggests a potential role as a receptor. Finally, expression of MUC1 mucin gene i n HTSE cells appears to be associated with differentiation of secretor y cells.