SEQUENCE AND EXPRESSION OF PROLINE-RICH PROTEIN MESSENGER-RNAS IN RATS AND MICE
Abstract
The translatable mRNA population of rat parotid glands is dramatically changed by ingestation of high-tannin sorghum or administration of the (beta)-agonist, isoproterenol. Proline-rich proteins are the major translation products of RNA isolated from the parotid glands of IPR-treated rats. Four recombinant plasmids were identified as containing cDNA coding for rat PRP mRNAs by hybrid-selected translation and immunoprecipitation of the translation products with anti-PRP antibodies. Hybrid selection and agarose gel purification of PPR mRNAs identified a minimum of nine RNAs coding for rat PRPs. IPR-treatment of mice was found to cause changes observed in rats. The rat PRP cDNAs were used to identify and isolate mouse PRP cDNAs. The relationships between the various rat and mouse cDNAs were studied by dot-blot hybridizations. These experiments allowed grouping of the PRP cDNAs according to homology. Northern blots showed the dramatic increase in rat and mouse PRP mRNA concentrations due to IPR-treatment. PRP mRNAs were not detected in the parotid glands of normal mice. Low levels of PRP mRNAs were detected in the parotid glands of normal rats. Rat PRP mRNA ranged in size from 1100 to 600 bases, and three major species of PRP mRNAs were observed in mice with apparent sizes of 1350, 1100, and 950 bases. There was an additional minor PRP mRNA species at about 650 bases. Sequence analysis of two homologous PRP cDNAs showed the presence of extensive internal repetition of sequence. A tandem repeat of 19 amino acids was present in the derived amino acid sequence of both the rat cDNA, pRP25, and the mouse cDNA, pMP1. The repeat had the general sequence of PPPPGGPQQXPPQGX(P/Q)QG where X was Lys, Arg, or Asn. The nucleotide sequences of the first 100 bases of the 5' end were also found to be homologous in 5 PRP cDNAs. Comparison of the mouse and rat PRP cDNAs along with data from human PRPs shows the PRPs to be relatively conserved through evolution.
Degree
Ph.D.
Subject Area
Biochemistry
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