GENOMIC ORGANIZATION OF THE HUMAN MUCIN GENE MUC5B - CDNA AND GENOMICSEQUENCES UPSTREAM OF THE LARGE CENTRAL EXON

The complete structure of the DNA encoding the polypeptide chain of hu man mucin MUC5B has been determined. In this paper, we report the full -length cDNA (3886 bp) and genomic (15,143 bp) sequences upstream of t he unusually large central exon of the human mucin gene MUC5B. This re gion, composed of 29 exons, encodes 1283 amino acid residues. Exon siz es vary from 44 to 262 bp, and intron sizes range from 87 to 1703 bp. We determined the 5'-end of 2MUC5B by performing rapid amplification o f cDNA ends-polymerase chain reaction experiments leading to the same length of the amplified product and by using primer extension experime nts. A putative translation start site was found at nucleotide +37. We compared the amino-terminal region of MUC5B with those of pro-von Wil lebrand Factor, MUGS and MUC5AC, and animal mucins, RMuc2, PSM, and FI M-B.1. The primary amino acid sequence with a high content of cysteine residues demonstrates a high degree of similarity with other members of the 11p15 mucin gene family, particularly MUC5AC. The complete geno mic organization and both full-length genomic and cDNA sequences of MU C5B have been elucidated. This gene contains 48 exons and encodes 5662 amino acid residues to give a polypeptide with a M-r approximately 60 0,000.