DNA complementary to parathyroid mRNA directs synthesis of pre-proparathyroid hormone in a linked transcription-translation system

Maize chloroplast DNA fragment encoding the large subunit of ribulosebisphosphate carboxylase

In vitro linked transcription-translation of chloroplast DNA has been used to show that the large subunit of ribulose-1,5-bisphosphate carboxylase [3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39] is encoded by Zea mays chloroplast DNA. A BamHI-generated chloroplast DNA sequence cloned in Escherichia coli is shown to direct the in vitro synthesis of this protein identified as large subunit by its size, serological properties, and limited proteolytic digestion products.

Parathyroid hormone and parathyroid hormone-related peptide, and their receptors

Parathyroid hormone (PTH) has a central role in the regulation of serum calcium and phosphate, while parathyroid hormone-related peptide (PTHrP) has important developmental roles. Both peptides signal through the same receptor, the PTH/PTHrP receptor (a class B G-protein-coupled receptor). The different biological effects of these ligands result from their modes of regulation and secretion, endocrine vs. paracrine/autocrine. The importance of PTH and PTHrP is evident by the variety of clinical syndromes caused by deficiency or excess production of either peptide, and the demonstration that intermittent injection of PTH increases bone mass, and thus provides a means to treat osteoporosis. This, in turn, has triggered increased interest in understanding the mechanisms of PTH/PTHrP receptor action and the search for smaller peptide or non-peptide agonists that have efficacy at this receptor when administered non-parenterally.

The molecular biology of parathyroid disease

Advances in molecular genetics have shed important new light on the understanding of the basis for human tumors. The application of these methods has allowed for characterization of endocrine neoplasms at a level of resolution that was not previously possible. A variety of molecular techniques have been applied to the study of parathyroid tumors at the DNA level. Studies of the clonal derivation of adenomas and hyperplasia suggest that these entities arise through fundamentally different mechanisms. The gene for parathyroid hormone (PTH) has been cloned and mapped within the human genome. In a small subset of parathyroid tumors, a rearrangement of the PTH gene has been described which may have contributed to their pathogenesis. A separate gene has been identified which appears to be responsible for the humoral hypercalcemia of malignancy. Chromosomal deletions which appear to be involved in the pathogenesis of multiple endocrine neoplasia type 1 have also been found in sporadic parathyroid adenomas. Characterization of tumors at the DNA level may make it possible to correlate specific genetic abnormalities with the biologic behavior of different parathyroid neoplasms and may be useful in distinguishing between adenoma, hyperplasia, and carcinoma.

Signal sequence of human preproparathyroid hormone is inactive in yeast

The biosynthesis of human preproparathyroid hormone (hpreproPTH) and the processing to mature parathyroid hormone (hPTH) was investigated in yeast. Cells were transformed with a plasmid that carried a fusion gene made of the yeast pyruvate kinase promoter, complementary DNA (cDNA) encoding a slightly modified form of hpreproPTH and the transcription termination signal from yeast triosephosphate-isomerase. In transformed yeast cells we identified a protein that was recognized by a PTH antiserum and, on gel electrophoresis, comigrated with hpreproPTH marker. The amino-terminal sequence of the protein was consistent with that of hpreproPTH, indicating that the hormone precursor is not processed. It was localized inside the cell, when analyzed in pulse-chase experiments by trypsin accessibility in intact and lysed spheroplasts. In contrast, when mRNA from these yeast cells and from human parathyroid tissue was translated into preproPTH in a reticulocyte lysate supplemented with canine pancreatic microsomes, the preproPTHs from both mRNAs were transported and cleaved with identical efficiencies. We conclude that hpreproPTH is synthesized in yeast but not recognized and processed like a precursor of a secreted protein by the yeast secretory apparatus.

The biology of SAA: identification of the inducer, in vitro synthesis, and heterogeneity demonstrated with monoclonal antibodies

Continued studies of the macrophage-derived mediator of SAA synthesis (SAA Stimulating Factor) confirm our previous observations that SAASF copurified with leukocytic pyrogen (LP) and lymphocyte activating factor (LAF). Moreover, new data demonstrate three separate isoelectric points for human LP-LAF-SAASF each of which possess the three biological activities. During the purification of 15,000 MW LP from crude stimulated mononuclear cell supernatants, only those fractions with pyrogenic activity in rabbits caused augmented stimulation of lymphocytes (LAF) and induced SAA synthesis in mice. Purified human LP stimulated isolated mouse hepatocytes in vitro to synthesize SAA in a dose-responsive manner. Colchicine treatment of hepatocytes led to decreased secretion of SAA into the medium and to an intracellular accumulation of SAA. Messenger RNA was isolated from the livers of endotoxin-stimulated mice and translated in a wheat-germ cell-free system. A major product was identified at 13-14,000 MW. Immunoprecipitation with anti-mouse AA identified several bands on autoradiography of polyacrylamide gels. These larger SAA precursors may account for the previously noted heterogeneity of human SAA, comprising at least 6 SAA isomers, of similar molecular weight but different solubility and electrophoretic charge characteristics. Two monoclonal antibodies (IgM-K and IgG1-K) have been prepared using standard cell hybridization techniques. They are directed at the variable COOH terminal region of SAA since they detect differences between the 6 human SAAs but do not react with human, monkey, dog or mouse AA proteins, human AP, C-reactive protein, IgG nor albumin. These antibodies will be useful in examining the origin, structure and function of SAA.

Nucleotide sequence of cloned cDNAs encoding human preproparathyroid hormone

We have cloned cDNA copies of human preproparathyroid hormone in Escherichia coli after insertion of double-stranded DNA into the Pst I site of plasmid pBR322 using the poly(dG) . poly(dC) homopolymer extension technique. Recombinant plasmids coding for preproparathyroid hormone were identified by filter hybridization assay using as a probe 32P-labeled bovine preproparathyroid cDNA. Nucleotide sequence analysis of five recombinant plasmids permitted the assignment of 74 nucleotides of the 5' noncoding region, the entire coding region of 345 nucleotides, and the entire 3' noncoding region of 348 nucleotides of the mRNA. The coding sequence predicts the previously unknown "pre" amino acid sequence and clarifies the hormone's amino acid sequence, which has been disrupted. The 5' noncoding region contains an AUG codon followed by a UGA stop codon before the authentic initiator codon. The 3' noncoding region is 120 nucleotides longer than in bovine preproparathyroid mRNA and contains two A-A-U-A-A-A sequences, potential signals for polyadenylation.

Messenger ribonucleic acids from pig intestinal mucosa direct synthesis of calcium-binding protein in a cell-free translation system

mRNA from pig duodenal mucosa directs synthesis, in a wheat-germ cell-free system, of two products precipitated by antiserum to pure calcium-binding protein. One of these products has a higher molecular weight than authentic calcium-binding protein, but, like the authentic protein, is heat-stable. The other protein co-migrates with pure calcium-binding protein on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, is stable on heating to 70 degrees C for 15 min and alters its elution position on ion-exchange chromatography depending on whether Ca2+ is present in or absent from the elution buffer. The synthesized protein has these properties in common with authentic calcium-binding protein.