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Biomedical subjects

J Vuust

Publications and source records attributed to J Vuust.

70 records · Page 4Linked to original sources
PubMed1983

Tumor-promoting phorbol esters inhibit procollagen synthesis at a pretranslational level in JB-6 mouse epidermal cells.

Collagen synthesis was inhibited in JB-6 mouse epidermal cells after exposure to 12-O-tetradecanoylphorbol-13-acetate under conditions leading to irreversible neoplastic transformation. In vitro translation and hybridization studies demonstrated a dramatic decrease in collagen mRNA in 12-O-tetradecanoylphorbol-13-acetate-treated cells, suggesting that the inhibition of collagen synthesis in response to 12-O-tetradecanoylphorbol-13-acetate is due to regulation at a pretranslational level.

Animals↗
PubMed1983

Control of type I collagen synthesis: evidence for pretranslational coordination of pro alpha 1 (I) and pro alpha 2 (I) chain synthesis in embryonic chick bone.

The normal type I collagen molecule contains two alpha 1 (I) chains and one alpha 2 (I) chain. In embryonic chick calvaria, the two-chains are synthesized in a 2:1 ratio, and total polysomes from this tissue contain twice as much mRNA for pro alpha 1 (I) as for pro alpha 2 (I). To further investigate the mechanism by which synthesis may be coordinated, RNA isolated from various cell fractions of embryonic chick calvaria was translated in a rabbit reticulocyte lysate cell-free system. The procollagen chain products were separated by gel-electrophoresis and densitometrically quantitated from autoradiograms of the gels. Total cellular RNA, total cytoplasmic RNA, and polysomal RNA each directed the synthesis of pro alpha 1 (I) and pro alpha 2 (I) in a proportion of 2:1, whereas no procollagen mRNA activity was found in nonpolysomal cytoplasmic RNA. These results indicate that in the chick bone cells, all compartments contain twice as much pro alpha 1 (I) mRNA as pro alpha (I) mRNA, and that virtually all procollagen mRNA in the cytoplasm in polysome-bound. The coordination of procollagen chain synthesis thus presumably occurs at a pretranslational level, through differential rates of formation and/or degradation of the two mRNAs.

Animals↗
PubMed1982

In vitro studies on the conversion of the biosynthetic precursor of renin.

The initial translation product of mouse submaxillary gland mRNA has a molecular weight of about 50,000. We have now translated renin mRNA in frog oocytes which are known to be able to remove the so-called "pre"- or "signal"- sequence from products of injected mRNAs. From these injected oocytes, we could precipitate with antirenin a 48,000 dalton polypeptide. Treatment with kallikrein or trypsin of the oocyte product resulted in a decrease in amount of this 48,000 dalton protein and a corresponding increase in a 45,000 dalton protein, precipitable with antirenin. We conclude that the initial translation product of renin mRNA is a preprorenin of molecular weight 50,000, which in oocytes is enzymatically cleaved to render 48,000 dalton prorenin. Although kallikrein may be a physiological activator of renin, it appears to be not the only one since no mature, 40,000 dalton renin was formed.

Animals↗
PubMed1981

Isolation and characterization of alpha-amylase messenger RNA from bank vole parotid glands. Evidence for two separate messenger RNAs coding for amylase and an amylase-related protein.

Bank vole saliva contains two glycogen-precipitable proteins, both of which show affinity for the alpha-amylase inhibitor cycloheptaamylose. One of these proteins, amylase, has a molecular weight of 55,000, judged from dodecylsulphate/acrylamide gel electrophoresis. The other has an apparent molecular weight of 59,000 and has no amylase activity. We report here that tryptic peptide maps as well as amino-acid composition analyses indicate extensive homology between the two proteins. We have also isolated total poly(A)-containing mRNA from amylase-rich bank vole parotid glands. These mRNAs were translated in the presence of [35S]methionine in an mRNA-dependent cell-free translation system from rabbit reticulocyte lysate. The radioactive translation products were examined by dodecylsulphate/polyacrylamide gel electrophoresis. Two major translation products with apparent molecular weights of approximately 56,500 and 60,500, respectively, were further characterized by tryptic peptide analyses. Our data indicate that the 56,500-Mr product is the biosynthetic precursor of amylase, whereas the 60,500-Mr translation product is a precursor of the 59,000-Mr amylase-like protein. Both precursors appear to contain extra peptide material, presumably as amino-terminal 'pre' or 'signal' peptides, in analogy with that found for other precursors of secretory proteins. Thus, amylase and the 59,000-Mr protein, although very similar, are translated from two separate mRNAs. These two messengers sediment in a sucrose gradient at about 17-S, corresponding to lengths of about 1,800 nucleotides.

Amino Acids↗
PubMed1980

IgE production in vitro by two rat myeloma tumor lines (IR2 and IR162).

Two IgE-synthesizing rat myeloma tumor lines (IR2 and IR162) were maintained in growing cultures that were viable for prolonged periods of up to three months in the presence of primary fibroblasts. The production of IgE by explanted tumor cells was studied in short-term and long-term cultures. The IR 162 tumor line retained expression of both IgE heavy (H) and light (L) chain synthesis for up to three months under in vitro conditions, while the IR2 tumor line initially lost H chain expression after approximately one month in culture, followed by subsequent loss of L chain about one month later. Total polysomal RNA extracted from IR2 cells, before and after loss of IgE-expression, was separated by sucrose gradient centrifugation, and gradient fractions were analysed for poly(A)-containing mRNA by a [3H]poly(U)binding assay. The results for the long-term IR2 cultures showed a disappearance of mRNA sedimenting at 18-20 S and 15 S, found to represent H and L chain mRNAs, respectively. Furthermore, no IgE L chain mRNA sequences could be detected in long-term IR2 cultures when analysed by hybridization assays, using as a probe a 3H-labelled DNA complementary to IgE L chain mRNA, L chain mRNA sequences were also absent from the nuclear RNA in long-term IR2 cultures. The loss of IgE synthesis in long-term cultures of IR2 cells therefore appears to be correlated with a concomitant loss of IgE mRNA sequences indicating a dedifferentiation in vitro modulated at the transcriptional level.

Animals↗
PubMed1975

Procollagen biosynthesis by embryonic-chick-bone polysomes. Estimation of the relative numbers of active proalpha1 and proalpha2 messenger ribonucleic acids.

Both total polysomes and polysomes of different size classes isolated from embryonic chick cranial bones were allowed to complete their nascent polypeptide chains in a cell-free system containing rabbit reticulocyte post-ribosomal supernatant fraction. In this system, no de novo initiation of polypeptide synthesis occurred. The product was analysed for relative content of proalpha1 and proalpha2, the precursors of the alpha chains of collagen, by dodecylsulphate-acrylamide gel electrophoresis as well as by paper electrophoresis following tryptic digestion. The results showed that the products of polysome protein synthesis contained proalpha1 and proalpha2 in the 2:1 ratio in which the corresponding alpha chains are present in native collagen, and that proalpha1 and proalpha2 synthesising polysomes are of the same size. These findings, in conjunction with results from a previous report (Vuust, J. and Piez, K.A. (1972) J. Biol. Chem. 247, 856-862) suggest that active messenger ribonucleic acids for the proalpha1 and proalpha2 chains, respectively, are present in the cells in a ratio of 2:1, and that the rates of initiation, elongation, termination and release from polysomes are all identical for the two chains.

Animals↗
PubMedDate not supplied

Analysis of FMR1 (CGG)n alleles and FRAXA microsatellite haplotypes in the population of Greenland: implications for the population of the New World from Asia.

The fragile X syndrome is caused by the expansion of a polymorphic (CGG)n tract in the promoter region of the FMR1 gene. Apparently the incidence of fragile X syndrome is rare in the population of Greenland. In order to examine population-related factors involved in stability of the (CGG)n sequence, DNA samples obtained randomly from the Greenlandic population were analysed for size and AGG interspersion pattern of the FMR1 (CGG)n region and associated DXS548-FRAXAC1 haplotypes. In addition a large Greenland family with unstable transmission in the premutation range was analysed. The (CGG)n allele sizes in the Greenland population showed a narrow distribution similar to that reported for Asian populations. DNA sequencing of alleles with 36 CGG repeats revealed an AGG(CGG)6 insertion previously reported exclusively in Asian populations and a high frequency of alleles with a (CGG)10AGG(CGG)9AGG(CGG)9 or (CGG)9AGG(CGG)9AGG(CGG)6AGG(CGG)9 sequence pattern was found. Thus the data confirm the Asian origin of the Greenlandic (Eskimo) population and indicates that some (CGG)n alleles have remained stable for 15-30,000 years, since the population of the New World arrived from Asia via the Bering Strait.

Alleles↗