title: Multiple transcripts of MUC3: evidence for two genes, MUC3A and MUC3B.
abstract: The MUC3 gene encodes a transmembrane mucin-type glycoprotein. A number of consistent single nucleotide changes were observed in different MUC3 cDNAs from a single individual, suggesting the presence of at least three different transcripts per individual. This transcript heterogeneity is due both to the existence of a second copy of the MUC3 gene and to allelic changes. Sequencing of the second MUC3 shows that it has the same C-terminal domain and intron/exon structure as the previously described MUC3. The tandem repeat domain has the same amino acid consensus sequence but shows more substitutions. The unique exonic sequences range from 94 to 100% identity at the nucleotide level and correspondingly few amino acid changes have been identified. The introns show around 95% identity. We propose to name this second gene MUC3B, MUC3A being reserved for the first MUC3 gene. MUC3B, like MUC3A, is expressed in intestine and Caco-2 cells.
authors.affiliation: MRC Human Biochemical Genetics Unit, University College London, 4 Stephenson Way, London, NW1 2HE, United Kingdom.
authors.forename: W S
authors.initials: WS
authors.lastname: Pratt
authors.forename: S
authors.initials: S
authors.lastname: Crawley
authors.forename: J
authors.initials: J
authors.lastname: Hicks
authors.forename: J
authors.initials: J
authors.lastname: Ho
authors.forename: M
authors.initials: M
authors.lastname: Nash
authors.forename: Y S
authors.initials: YS
authors.lastname: Kim
authors.forename: J R
authors.initials: JR
authors.lastname: Gum
authors.forename: D M
authors.initials: DM
authors.lastname: Swallow
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D018938:Caco-2 Cells; D003001:Cloning, Molecular; D005091:Exons / Q000235:genetics; D015870:Gene Expression; D020131:Genes, Duplicate / Q000235:genetics*; D014644:Genetic Variation / Q000235:genetics; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000196:embryology; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D055263:Mucin-3; D009077:Mucins / Q000737:chemistry / Q000235:genetics*; D011110:Polymorphism, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D020449:Repetitive Sequences, Amino Acid / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: C524652:MUC3A protein, human; C524655:MUC3B protein, human; D055263:Mucin-3; D009077:Mucins; D012333:RNA, Messenger