| Both recombinant DNA and cytogenetic techniques were used to analyze the human salivary protein complex (SPC). A plasmic, pPRP 2.2, containing the human genomic DNA coding for an SPC gene, PmS, was used to produce a human parotid gland cDNA library. cDNAs from this library ranged in size from 200-1800 bp with SPC cDNAs 200-750 bp in size. The DNA sequence representing part of the SPC coding region of a cDNA (EO27) was determined and found to match that of cP7, and SPC cDNA produced by researchers at the University of Wisconsin (Maeda et al., 1985). RNAs coding for SPC genes are larger than expected from estimates of protein sizes. Northern blots probed with an SPC cDNA, EO27, yielded five species of RNA with molecular weights 0.9-1.8 kb. Cell-free translation studies indicate six major SPC products which range in size from 15,500 (Pr 1) to ca. 30-45,000 (those of the basic proteins). These molecular analyses indicate that some SPC proteins are synthesized as large precursors that are cleaved posttranslationally, a theory originally proposed by Karn et al. (1977;1979) and confirmed by the DNA sequences of EO27 and other SPC cDNAs (Maeda et al., 1985). The molecular analyses represent the first detailed study of SPC mRNA, protein, and cDNAs.;In situ hybridization with a human SPC genomic fragment, pPRP 2.2, and an SPC cDNA, EO27, localized the SPC to human chromosome band 12p13.2. Initial localization was performed with the genomic fragment, and was confirmed with the cDNA, EO27. The results of in situ hybridization ruled out linkage of the SPC to human chromosome 6, and indicate that the SPC is probably smaller than the 15 million base pairs estimated from recombinational data. Both cytogenetic and molecular analyses have aided in explaining aspects of the SPC. |
