A single highly-polymorphic autosomal gene locus PUM codes for a family of mucin-type glycoproteins, separable by SDS-gel electrophoresis, which we first identified in human urine1,2. The locus also codes for glycoproteins which are abundant in several other normal epithelial tissues and body fluids, including milk, and in tumours of epithelial origin3. These mucin-type glyco-proteins seem to be very immunogenic in rodents and, in a search for epithelial specific or tumour-associated antigens, a large num-ber of related antibodies have been isolated4-9 which bind to the PUM-coded mucins3. Many of the antibodies show a pronounced tumour specificity on immunohistology10-13 and are being used widely in cancer diagnosis in vitro9-12 and in vivo11,14 and even in cancer therapy15. To investigate the expression of these antigens in normal and malignant cells complementary DNA coding for the mammary mucin has been isolated16. Here we present evidence obtained using this cDNA that the PUM locus is a hypervariable 'minisatellite' region of human DNA similar to those described by several groups17-25, but which is novel in that it is transcribed and translated, and that the same polymorphism is demonstrable in the expressed gene product.
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