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At least 19 recordsLinked to original sources
PubMed1976

Induction of vitellogenin synthesis by estrogen in avian liver: relationship between level of vitellogenin mRNA and vitellogenin synthesis.

We have investigated the estrogen-mediated induction of vitellogenin synthesis in rooster liver. We compared the concentrations of vitellogenin messenger RNA (mRNA) in the liver with the concentrations of vitellogenin in the sera of roosters that had recieved various treatments with estrogen. We found no vitellogenin mRNA in the livers of the unstimulated roosters. An initial injection of estrogen was attended by de novo synthesis of vitellogenin mRNA in the liver and accumulation of vitellogenin in the serum. When vitellogenin was no longer present in the serum or liver (the "post-estrogen-serum-negative" state), the liver was found to contain appreciable amounts of vitellogenin mRNA. This mRNA was of the same size as that found in the liver of the rooster actively synthesizing vitellogenin in response to estrogen. Whereas vitellogenin mRNA was in large polysomes in the livers of the roosters actively synthesizing vitellogenin, the vitellogenin mRNA in the liver of the post-estrogen-serum-negative rooster was not associated with polysomes. The possible relevance of these findings to the fact that the rooster responds differently to a primary stimulation with estrogen than to subsequent stimulations is discussed.

Animals↗
PubMed1975

Vitellogenin synthesis in the avian liver. Vitellogenin is the precursor of the egg yolk phosphoproteins.

Administration of estrogen to roosters induces the synthesis of egg yolk phosphoproteins in the liver. We have demonstrated that these proteins are synthesized in the form of a large precursor, vitellogenin, and that vitellogenin is the only phosphoprotein found in the plasma of the estrogen-treated rooster. Vitellogenin is cleaved to form the egg yolk phosphoproteins, lipovitellin, and phosvitin. We have purified vitellogenin to hemogeneity by two methods: chromatography on diethylaminoethyl-52-cellulose and affinity chromatography on an antibody-Sepharose column. Antibodies were elicited in rabbits and sheep by immunization with vitellogenin and lipovitellin, and these antibodies were purified by affinity chromatography on antigen-Sepharose columns. We found that phosvitin was not immunogenic in its native form or in any of the large variety of modified forms we have tested. We have determined the molecular weights of native and denatured vitellogenin and have examined the immunological relationship between vitellogenin and lipovitellin. On the basis of these studies, together with data from phosphate analyses, we suggest that avian vitellogenin is composed of two polypeptides, each of which has a molecular weight of approximately 240,000 and contains within it lipovitellin and two phosvitins.

Animals↗
PubMed1976

Characterization of polysomes from Xenopus liver synthesizing vitellogenin and translation of vitellogenin and albumin messenger RNA's in vitro.

1. Conditions are described for the isolation of polysomes from the liver of Xenopus laevis. The method involves homogenization of liver in 0.2 M Tris-HCl pH 8.5, treatment with 2% Triton X-100 and subsequent sucrose density gradient fractionation of polysomes from a 10000 X g supernatant. 2. Vitellogenin synthesis was induced in male Xenopus liver by oestradiol treatment. Polysomes were isolated and vitellogenin-synthesizing polysomes characterized by their association with monospecific 125 I-labelled rabbit anti-vitellogenin antibody and by reaction with rabbit anti-vitellogenin immunoglobulins followed by indirect immunoprecipitation with goat anti-rabbit antibody. 3. Changes in liver polysome content following oestrogen treatment of male Xenopus are correlated with the appearance of vitellogenin synthesis using an organ culture assay. 4. RNA extracted from livers of oestradiol-treated male Xenopus and from purified polysomes is shown to code for the synthesis of vitellogenin-specific immunoprecipitable polypeptides in a rabbit reticulocyte cell-free protein-synthesizing system, a major component having a molecular weight of 210000. Xanopus liver RNA is also shown to code for the synthesis of an albumin-specific immunoprecipitable polypeptide of 74000 molecular-weight which coelectrophoresed with Xenopus albumin.

Albumins↗
PubMed1976

Estradiol-induced synthesis of vitellogenin. III. The isolation and characterization of vitellogenin messenger RNA from avian liver.

The messenger RNA of the hormone-induced protein vitellogenin was isolated from the liver of estrogen-treated roosters. Starting from total polysomal RNA, the vitellogenin messenger was purified 67-fold by oligo (dT)-cellulose chromatography and sizing on a sucrose gradient. The messenger was translated in vitro into a 170 000 dalton polypeptide chain, having the immunochemical characteristics of vitellogenin. From electrophoretic and immunochemical analysis of the in vitro product of translation at least 63% of the messenger activity of the RNA preparation could be attributed to vitellogenin mRNA. Gel electrophoresis of the most purified fraction revealed residual contamination with the larger ribosomal RNA species. The molecular weight of the messenger RNA molecule, obtained by contour length measurements in the electron microscope, lies between 2.5 - 10(6) and 2.8 - 10(6).

Animals↗
PubMed1978

Estradiol-induced accumulation of vitellogenin mRNA and secretion of vitellogenin in liver cultures of Xenopus.

Explants of male Xenopus liver maintained in a serum-free culture medium respond to stimulation by 2 X 10(-8) M 17beta-estradiol with an increasing rate of accumulation of vitellogenin mRNA, as revealed by hybridization of cDNA to the total cytoplasmic RNA extracted from the cultures. A similar response is observed for secretion of 32PO4-labeled vitellogenin into the culture medium. The in vitro response is improved in liver tissue of prestimulated animals, and by adaptation of liver explants to the culture medium prior to hormone treatment, but attains only about 10% of the in vivo response. Since essential features of the in vivo response are maintained in liver explants, organ culture appears suitable for investigating initial events of estradiol action leading to enhanced synthesis of vitellogenin.

Animals↗
PubMed1992

Role of the lysine and arginine residues of vitellogenin in high affinity binding to vitellogenin receptors in locust oocyte membranes.

A specific cell surface receptor mediates the endocytosis of the yolk protein vitellogenin (VTG), a lipoglycoprotein, into growing oocytes of the insect Locusta migratoria. The ability of the VTG receptor to recognize VTG was analyzed in binding tests after modification by five lysine-specific and two other reagents. Progressive chemical modification of the lysyl and arginyl residues resulted in reduction or loss of the derivatized VTG to compete for binding to the VTG receptor with unmodified VTG. Although the precise role of the lysine residues in receptor binding remains to be defined we conclude that they are involved in expression of a recognition site interacting with the binding domain of the VTG receptor. Sulfhydryl groups are not involved in the conformation of the recognition site or binding ability of VTG.

Acetylation↗
PubMed1976

In vitro translation and estradiol-17beta induction of Xenopus laevis vitellogenin messenger RNA.

Administration of estradiol-17beta to male Xenopus laevis induces synthesis and secretion by the liver of the egg yolk precursor protein vitellogenin. RNA extracted from livers of estradiol-17beta-treated Xenopus laevis directs the synthesis of the entire 200,000-dalton vitellogenin monomer in a cell-free protein synthesizing system derived from rabbit reticulocytes. Vitellogenin synthesized in vitro was isolated and quantitated by indirect immunoprecipitation and identified by comparison to authentic [14C]vitellogenin. The in vitro product and [14C]vitellogenin co-migrate on electrophoresis in sodium dodecyl sulfate-polyacrylamide gels and they exhibit identical immunoprecipitation curves. Xenopus laevis vitellogenin messenger RNA has a sedimentation coefficient of approximately 30 S in sucrose density gradients. It can be purified approximately 60-fold from cell RNA by poly(U)-Sepharose chromatography and therefore appears to contain a polyadenylate sequence. Vitellogenin mRNA and vitellogenin synthesis in vivo could not be detected in unstimulated male Xenopus laevis. The relative rate of vitellogenin synthesis and the level of vitellogenin mRNA were determined at various times following the administration of estradiol-17beta. Vitellogenin synthesis is maximal 12 days after estradiol-17beta administration when it comprises approximately 70% of cell protein synthesis. The level of vitellogenin mRNA and the intracellular rate of vitellogenin synthesis exhibit a close correspondence from 4 to 16 days after administration of estradiol-17beta.

Animals↗
PubMed1976

Translation of Xenopus liver messenger RNA in Xenopus oocytes: vitellogenin synthesis and conversion to yolk platelet proteins.

Xenopus liver vitellogenin and albumin mRNAs injected into Xenopus oocytes are correctly translated, as shown by specific immunoprecipitation and co-electrophoresis with purified Xenopus vitellogenin (molecular weight 210,000 daltons) and albumin (molecular weight 72,000 daltons). Vitellogenin made in oocytes under the direction of injected liver mRNA is unstable compared to other proteins made on injected messengers (such as albumin and globin) and endogenous oocyte proteins (including actin), the half-life of newly made vitellogenin being about 8 hr. Pulse-chase experiments with 35S-methionine show vitellogenin to be a precursor to yolk platelet lipovitellin (molecular weight 120,000 daltons), while 3H-serine labeling demonstrates conversion to phosvitin (molecular weight 34,000 daltons). In contrast, injected 3H-serine 35S-methionine-labeled Xenopus vitellogenin protein is not converted to yolk platelet proteins and is degraded rather slowly (half-life, 23, 29 hr). Phosphorylation of serine residues in phosvitin can be detected in oocytes injected with 32PO4 or gamma-32P-ATP; thus exogenously derived yolk platelet protein is further modified, or turned over, once it is within the oocyte. Moreover, vitellogenin made in oocytes programed with liver mRNA is phosphorylated. Thus phosphorylation, assembly into yolk platelets, and cleavage are events that do not require vitellogenin supplied by the normal pathoways involved in yolk formation (synthesis and post-translational modification in the liver, transport in the serum, and follicle cell-dependent pinocytosis). Vitellogenin mRNA sediments at about 29S in a sucrose-SDS gradient, while albumin messenger peaks at 16S; both species contain poly(A). These liver mRNAs are functionally stable in oocytes for at least 5 days. Vitellogenin-forming activity, relative to albumin, actin, or total endogenous activity, increases with time, and the final rate of 2-2.5 times the initial rate is only reached 3 days after injection. The potentiation effect probably stems from an increase in the efficiency of translation of vitellogenin mRNA. The availability of homologous mRNAs now permits injected messenger to be used as a valide probe of oocyte function; the biological activity of mRNA from a non-ovarian Xenopus tissue proves that some at least of the translational systems within the Xenopus oocyte are not cell type-specific. Moreover, the whole cell system is eminently suitable for assaying putative translational (and possibly transcriptional) control elements from frog liver.

Albumins↗
PubMed1978

Primary induction of vitellogenin mRNA in the rooster by 17beta-estradiol.

We have studied the kinetics of vitellogenin mRNA accumulation in rooster liver after a primary injection of 17beta-estradiol. The levels of vitellogenin mRNA have been determined both by hybridization of total cellular RNA to vitellogenin cDNA and by translation of vitellogenin mRNA in a wheat germ cell-free system. The results obtained by both methods of analysis are in good agreement and indicate that vitellogenin mRNA is present in the liver of normal roosters at a level of 0-5 molecules per liver cell and increases in amount during the 3 days following injection of estrogen, reaching a level of almost 6000 molecules per cell at the peak of the response. The level of vitellogenin mRNA declined exponentially during the next 14 days with a half-life of 29 hr, reaching a level of less than 10 molecules per cell at 17 days after injection of the hormone. The levels of vitellogenin mRNA after stimulation with estrogen have been correlated with the in vivo rate of synthesis of the vitellogenin polypeptide. The results indicate that the rate of vitellogenin synthesis is closely correlated with the level of vitellogenin mRNA. On the basis of these findings, we conclude that vitellogenin mRNA does not exist in the liver in an untranslated form after withdrawal from estrogen.

Animals↗
PubMed1979

Two processing steps in maturation of vitellogenin polypeptides in Drosophila melanogaster.

Synthesis of the three vitellogenin polypeptides (molecular weights of 44,000, 45,000, and 46,000) of Drosophila melanogaster has been analyzed in vivo and in a cell-free system. After labeling periods in vivo, the three vitellogenin polypeptides were made as the principal synthetic products of the female fat body. During a short (0.5 min) labeling period, they were identified as discrete species on two-dimensional gels. Two of the polypeptides have molecular weights of 45,000 and a third has a molecular weight of 44,000. After longer labeling periods (5-45 min) the three mature vitellogenins appeared. Both immunoprecipitation and peptide mapping confirmed that the species labeled at 0.5 min are immature forms of the vitellogenin polypeptides. In vitro translation of poly(A)-RNA from female fat body indicated another processing step in vitellogenin synthesis. Three polypeptides were obtained that were identified as precursors of the vitellogenins on the basis of immunoprecipitation and peptide mapping. Two of the translation products have a molecular weight of 46,000 and the third has a molecular weight of 45,000. Because the vitellogenins are secreted proteins, we interpret the higher molecular weight of the in vitro translation products as being due to signal peptides.

Adipose Tissue↗
PubMed1976

Protein incorporation by isolated amphibian oocytes. V. Specificity for vitellogenin incorporation.

Macromolecules of vitellogenin were sequestered by Xenopus laevis oocytes 20-50 times (on a molar basis) more rapidly than other proteins tested. Selectivity for vitellogenin did not appear to involve molecular size or charge. The Km for vitellogenin incorporation was at least several orders of magnitude less than that for bovine serum albumin (BSA). At concentrations less than 10 mg-ml-1, BSA did not measurably compete with vitellogenin; a slight, apparent competition observed above a BSA concentration of 10 mg-ml-1 was probably spurious. Above a concentration of 2 mg-ml-1, vitellogenin promoted BSA incorporation by about 40%. These results are consistent with the notion that vitellogenin binds to specific receptor sites on the oocyte membrane and is subsequently internalized by micropinocytosis. Other proteins, such as BSA, which do not compete with vitellogenin are most likely to be incorporated by adventitious engulfment during micropinocytosis.

Animals↗
PubMed1977

Estrogen induction of plasma vitellogenin in the cockerel: studies with a phosvitin antibody.

The effects of estrogen on plasma vitellogenin have been studied in the cockerel by immunoprecipitation techniques using an antiserum prepared against the egg yolk phosphoprotein, phosvitin. The antiserum gave precipitin lines of complete identity to phosvitin and to vitellogenin which was isolated from hen plasma by DEAE-cellulose chromatography and by affinity chromatography using anti-phosvitin coupled to Sepharose 4B. The cross-reactivity of vitellogenin and phosvitin adds support to the concept that plasma vitellogenin is the precursor phosphoprotein of egg yolk phosvitin. In the three-week old cockerel, anti-phosvitin produced no detectable immunoprecipitate in the plasma. However, after a single sc injection of diethylstilbestrol (2.5 mg), plasma vitellogenin levels began to increase at 4 h and reached a maximum 20-30 h after hormone administration. The increase in plasma levels of triglyceride paralleled those of vitellogenin. These studies suggest that there is no significant time lag in the estrogenic induction of plasma vitellogenesis in the cockerel, the longer lag periods observed by other investigators may be a function of the sensitivity of the assays used for detecting vitellogenin.

Amino Acids↗
PubMed1977

In vitro translation of avian vitellogenin messenger RNA.

Administration of 17beta-estradiol to roosters induced the synthesis of vitellogenin in the liver. The mRNA that specifies this protein has been purified from the livers of estrogen-treated roosters and has been shown to have a molecular weight of 2.3 X 10(6) (Deeley, R.G., Gordon, J.I., Burns, A.T.H., Mullinix, K.P., Bina-Stein, M., and Goldberger R.F. (1977) J. Biol. Chem. 252, 8310-8319). In order to rigorously establish the identity of the polypeptide specified by this mRNA, we used a staphylococcal nuclease-treated, mRNA-dependent wheat germ cell-free translation system capable of synthesizing polypeptides as large as vitellogenin (monomer Mr = 240,000). Vitellogenin mRNA directs the in vitro synthesis of a polypeptide with the following features: (a) it co-migrates with authentic vitellogenin in SDS-polyacrylamide gels; (b) it is highly enriched for serine but is not phosphorylated; (c) it is immunoprecipitated by purified, monospecific, anti-vitellogenin antibody; and (d) it has an unusual cyanogen bromide cleavage pattern characteristic of vitellogenin. The most striking characteristic of the cyanogen bromide cleavage products is an extremely large polypeptide (Mr = 90,000) that contains two phosvitins. The kinetics of incorporation of serine and methionine into vitellogenin synthesized in the wheat germ cell-free translation system indicates that the phosvitins are located near the COOH-terminal portion of the molecule.

Animals↗
PubMed1992

Sequence of lamprey vitellogenin. Implications for the lipovitellin crystal structure.

The amino acid sequence of lamprey vitellogenin has been predicted from the nucleotide sequence of cloned cDNA. The sites of proteolytic cleavage that produce the lipovitellin complex from the vitellogenin have been located by comparing the N-terminal sequences of two lamprey lipovitellin polypeptides with the predicted sequence. These results also confirm that the vitellogenin sequence derived here corresponds to the lipovitellin complex for which the crystal structure has been solved previously. Predictions of secondary structure indicate that the region most likely to correspond to the large alpha-helical domain of the crystallographic model consists of vitellogenin residues 300 to 600. Similar to the lipovitellins of Xenopus laevis, lamprey lipovitellin appears to lack approximately 200 C-terminal residues that are present in vitellogenin. However, the lamprey lipovitellin differs from those of Xenopus and chicken in two respects. First, most of the serine-rich domain that is present as the phosvitin polypeptide in the lipovitellins of the higher vertebrates appears to be lost in the maturation of lamprey vitellogenin to lipovitellin. Second, the domains that constitute the large lipovitellin-1 polypeptide in Xenopus and chicken are present in two polypeptides in lamprey, owing to an additional proteolytic processing event.

Amino Acid Sequence↗
PubMed1979

Induction of vitellogenin and growth of implanted oocytes in male cockroaches.

Vitellogenins are yolk protein precursors that are synthesised in the liver of lower vertebrates in response to ovarian hormones, and in the fat body tissue of insects, under the influence, in most species, of juvenile hormone (JH) from the corpora allata (CA). Vitellogenins are normally restricted to females, although in male amphibians and roosters their synthesis can be induced artificially by the injection of oestrogens. Thus female specificity is maintained by hormonal differences between adult males and females. In insects, on the other hand, because the CA of adults of both sexes are active, it appeared that male fat body could not normally respond to JH by synthesising vitellogenin. However, precise JH synthetic rates of male CA are only known in Schistocerca gregaria and Diplopterapunctata, in which species they are low compared to the rates in the female glands. The absence of vitellogenin in adult males could thus be due to inadequate JH titres. We report here that synthesis of vitellogenin can indeed be induced in males of Diploptera by implantation of female CA or application of Diploptera by implantation of female CA or application of a JH analogue, ZR512 (Zoecon), and that implanted oocytes take up the vitellogenin.

Animals↗