The transcripts of the apomucin genes MUC2, MUC4, and MUC5AC are large and appear as distinct bands

RNA from four colorectal carcinoma cell lines was prepared and analysed in Northern blots using probes for the MUC2, MUC4, and MUC5AC mucin apoprotein genes. The sizes of the transcripts were very large, in the order of at least 12-16 kb. The presence of distinct bands is in contrast to earlier reports, where these transcripts showed extensive polydispersity. RNA from rat small intestine was also prepared and probed with cDNA for the rat Muc2 mucin gene. This analysis also showed a large and discrete hybridizing band, indicating that apomucin mRNA of well-defined size can be obtained also from a tissue with high endogenous RNase activity.