Human pregnancy-specific beta 1 glycoprotein is encoded by multiple genes localized on two chromosomes

A human genomic library was screened with a mixture of two cDNA probes, with one covering the 5' coding sequence and the other containing the 3'-end portion of human pregnancy-specific beta 1 glycoprotein (SP1). Seventeen clones were identified, all of which carried insert fragments capable of hybridizing with the cDNA probe. Insert size of these clones varied from 15.0 to 19.8 kb. Partial restriction maps were constructed, which demonstrated the presence of at least seven groups of unique SP1 genomic clones and suggested the possibility of multiple genes coding for SP1. The multigene nature of SP1 was confirmed by hybridization of the SP1 cDNA probe to multiple bands on Southern blots of human genomic DNA. Further analysis with chromosomal DNA dot blot demonstrated the presence of homologous sequences on the X chromosome and autosomal chromosome 6. Thus, human SP1 is apparently coded for by more than one gene residing on the X and 6 chromosomes.