Characterization and molecular cloning of a novel MUC1 protein, devoid of tandem repeats, expressed in human breast cancer tissue

Eur J Biochem. 1994 Sep 1;224(2):787-95. doi: 10.1111/j.1432-1033.1994.00787.x.


The human breast cancer marker protein, MUC1, is a polymorphic transmembrane molecule containing a large extracellular domain that is primarily composed of a variable number of highly conserved 20-amino-acid tandem repeats. We report here the detection of a novel invariantly sized 1.2-kb MUC1 mRNA, in addition to the large polymorphic mRNAs, by probing Northern blots with MUC1-cDNA-unique-sequence probes. The nucleotide sequence of this novel MUC1 mRNA demonstrates that it is identical to the MUC1 cDNA sequences downstream and upstream to the tandem-repeat array of the transmembrane form of MUC1. However, it contains neither the central tandem repeat array itself nor its directly flanking sequences that are deleted by a differential splicing event utilizing splice acceptor and donor sequences 5' and 3' to the tandem-repeat array. The splice event retains, downstream to the splice acceptor site, an open reading frame identical to that of the repeat-array-containing MUC1 thereby generating the novel MUC1/Y protein. Cells transiently transfected with the novel MUC1/Y cDNA express the MUC1/Y protein that is modified by glycosylation. The MUC1/Y protein is also readily detected in human breast cancer cells grown in vitro. Furthermore, primary breast cancer tissue samples demonstrate significant levels of the MUC1/Y protein whereas expression in tissue adjacent to the tumor is undetectable. Molecular characterization presented here, of the novel MUC1/Y molecule lacking the repeat array, suggests that it is likely to play a role distinct to that of the polymorphic repeat-array-positive MUC1 protein and that it may act as a new marker protein for human breast cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Blotting, Northern
  • Breast Neoplasms / metabolism*
  • Cell Line
  • Cloning, Molecular
  • DNA Primers
  • Gene Expression
  • Haplorhini
  • Humans
  • Membrane Glycoproteins / biosynthesis*
  • Membrane Glycoproteins / chemistry
  • Molecular Sequence Data
  • Mucin-1
  • Mucins / biosynthesis*
  • Mucins / chemistry
  • Neoplasm Proteins / biosynthesis*
  • Oligonucleotide Probes
  • Polymorphism, Genetic
  • RNA, Messenger / biosynthesis
  • RNA, Messenger / chemistry
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / chemistry
  • Repetitive Sequences, Nucleic Acid
  • Transfection
  • Tumor Cells, Cultured


  • DNA Primers
  • Membrane Glycoproteins
  • Mucin-1
  • Mucins
  • Neoplasm Proteins
  • Oligonucleotide Probes
  • RNA, Messenger
  • Recombinant Proteins

Associated data

  • GENBANK/X80761