Characterization and molecular cloning of a novel MUC1 protein, devoid of tandem repeats, expressed in human breast cancer tissue.
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.
Zrihan-Licht
S
S
Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel.
Vos
H L
HL
Baruch
A
A
Elroy-Stein
O
O
Sagiv
D
D
Keydar
I
I
Hilkens
J
J
Wreschner
D H
DH
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D001943:Breast Neoplasms / Q000378:metabolism*; D002460:Cell Line; D003001:Cloning, Molecular; D017931:DNA Primers; D015870:Gene Expression; D000882:Haplorhini; D006801:Humans; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000737:chemistry; D008969:Molecular Sequence Data; D018396:Mucin-1; D009077:Mucins / Q000096:biosynthesis* / Q000737:chemistry; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D015345:Oligonucleotide Probes; D011110:Polymorphism, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis / Q000737:chemistry; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D012091:Repetitive Sequences, Nucleic Acid; D014162:Transfection; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D008562:Membrane Glycoproteins; D018396:Mucin-1; D009077:Mucins; D009363:Neoplasm Proteins; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D011994:Recombinant Proteins