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Immunochemical isolation and characterization of vitellogenin mRNA from liver of estradiol-treated chicks.

Vitellogenin mRNA was purified through three steps. A heavy polysome fraction was obtained by discontinuous sucrose density gradient centrifugation, vitellogenin polysomes were immunoprecipitated with affinity-chromatography-purified anti-lipovitellin IgG and goat anti-rabbit IgG, the enriched mRNA was isolated on a poly(U)-Sepharose column. As judged by its specific activity in a reticulocyte lysate system, vitellogenin mRNA has been enriched a 1000-fold with a recovery of 30%. On 99% formamide 3.4% polyacrylamide gels vitellogenin mRNA has an Mr of 2.4-2.5 X 10(6) and codes for a peptide of Mr 240000, which under our incubation conditions is partially degraded to smaller peptides.

Animals

Hormonal control of vitellogenin synthesis in avian liver.

Estradiol induces the synthesis of vitellogenin in the avian liver. We describe the precursor-product relationship between vitellogenin and the yolk proteins phosvitin and lipovitellin. The high rate of vitellogenin synthesis is a consequence of the accumulation of a stable messenger RNA. We suggest that estradiol acts at the level of the genome by opening a hitherto non-transcribed gene.

Animals

Synthesis of vitellogenin, an attractive model for investigating hormone-induced gene activation.

The estrogen-induced synthesis of vitellogenin in the frog Xenopus and the chicken is an attractive system for investigating the molecular events leading to the activation of a specific gene. In this review article the events occurring at the level of the protein and mRNA in the cytoplasm are discussed. The available data show that the induction of vitellogenin synthesis is due to the accumulation of the corresponding vitellogenin mRNA in the cytoplasm. This suggests that transcriptional or posttranscriptional events in the nucleus are activated by the hormone. The few experiments investigating the processes in the nuclear compartment are reviewed.

Animals

Localization of vitellogenin and serum albumin in hepatic parenchymal cells of normal and estradiol-treated immature chickens.

The localization of albumin and vitellogenin was determined in liver sections from control and estradiol-treated chickens by two different immunocytochemical techniques: (1) The sandwich technique with rabbit anti-lipovitellin or rabbit anti-albumin IgG and fluor. escent goat anti-rabbit IgG and (2) the mixed aggregation immunocytochemical technique with anti-lipovitellin IgG and fluorescent lipovitellin. The results show that the antibody against albumin bound only to all liver parenchymal cells. Furthermore, the fluorescence intensity was equally strong in the portal, intermediate and central zones of the lobules. The fluorescent stain for vitellogenin was not above background in livers of control chicks but was far above background in estradiol-treated chicks. As with albumin the fluorescent stain was distributed equally among the parentchymal cells. The results were quantitatively the same 2 and 4 days after estradiol treatment. The relative rates of synthesis and the concentrations of albumin and vitellogenin correlate well with values obtained for tissue sections by immunocytochemical techniques.

Animals

In vitro RNA synthesis and expression of vitellogenin gene in isolated chicken liver nuclei.

Optimal conditions for prolonged in vitro synthesis of RNA in isolated chicken liver nuclei have been described. It is shown by incorporation of gamma32P-GTP into RNA, analysis of the product on sucrose density gradient, and digestion with alkaline phosphatase and ribonuclease A that there is reinitiation of RNA synthesis. Polynucleotide kinase activity has been ruled out as explanation for the incorporation of gamma32P-GTP. alpha-Amanitin inhibits RNA synthesis by about 50%. Nuclei prepared from estradiol-treated chicks have twice the RNA synthesis activity as the controls. RNA is synthesized in the presence of Hg-UTP and the mercurated product separated by affinity chromatography on sulfhydryl-Sepharose column under stringent conditions. Vitellogenin mRNA sequences are measured by hybridization with DNA complementary to vitellogenin mRNA. Estradiol treatment leads to a 10-fold increase in vitellogenin mRNA sequences.

Amanitins

Characterisation of bacterial clones containing DNA sequences derived from Xenopus laevis vitellogenin mRNA.

A 1700 nucleotide DNA sequence derived from Xenopus vitellogenin mRNA has been cloned in the bacterial plasmid pBR322. The identity of the cloned sequence was verified in two ways. Firstly, the plasmid DNA was shown to hybridise to an RNA of the correct size (6,700 nucleotides). This was shown by in situ hybridisation to electrophoretically separated RNA and also by the formation of "R-loops" with purified vitellogenin mRNA. Then, using a novel procedure in which plasmid DNA covalently bound to diazotised paper is used to select complementary mRNA sequences, the cloned sequence was shown to hybridise to an mRNA which directed the synthesis of vitellogenin when translated in a reticulocyte lysate cell-free system.

Animals

Distribution of estradiol receptor and vitellogenin gene in chick liver chromatin fractions.

The distribution of estradiol receptor and vitellogenin gene was studied in estradiol stimulated chick liver chromatin fractions prepared by limited DNAse II digestion and MgCl2 precipitation. The receptor was found in all fractions, undigested chromatin (P1), Mg2+ insoluble chromatin (P2) and Mg2+ soluble chromatin (S2). This last fraction was rich in acidic proteins, had a high protein:DNA ratio (7.0 w/w), contained 28% of rapidly labelled RNA, 20% of the receptor, 3-5% of chromatin DNA and showed a 2 fold enrichment of vitellogenin DNA sequences over unfractionated chromatin as well as P1 and P2 DNA. On isopycnic metrizamide gradients, all chromatin fractions showed a receptor peak banding at 1.23 g/cm3, the density of nucleoproteins. Hybridization experiments showed that the DNA banding at this density in fraction S2 was enriched 4 fold in vitellogenin DNA sequences over unfractionated chromatin as well as P1 and P2 DNA. These results suggest an association of hormone receptor complex with nucleoprotein structures of an apparently active chromatin fraction.

Animals

Electron-microscopic demonstration of terminal and internal initiation sites for cDNA synthesis on vitellogenin mRNA.

cDNA synthesized on purified vitellogenin mRNA from Xenopus liver was hybridized to the template in formamide/urea at 22 degrees C to avoid degradation of the RNA. The hybrids formed were visualized by spreading for electron microscopy. Contour length measurements proved that most of the RNA molecules in the hybrids were still intact showing the expected molecular weight of 2.3 x 10(6). The hybridized cDNA corresponded on the average to 12% of the RNA length. In about 80% of the molecules the cDNA was located at one end. Since cDNA synthesis was primed by oligo(dT), the terminal duplex region marks the 3' end of the vitellogenin mRNA molecule. Internal duplex regions were mainly located at a specific position starting about 2800 nucleotides from the 3' end. Since the cDNA hybridizing at the internal position could specifically be synthesized on a vitellogenin RNA fragment isolated on poly(U)-Sepharose as an oligo(A)-containing RNA, we conclude that cDNA synthesis is not only initiated by the poly(A) of the 3' end, but also by a specific internal sequence.

Animals

Codon-specific serine transfer ribonucleic acid synthesis in avian liver during vitellogenin induction.

The relative rates of synthesis of two major tRNASer species in rooster liver were simultaneously assessed during induction by estradiol-17beta of the synthesis of a serine-rich phosphoprotein, vitellogenin. The relative rates of tRNA synthesis were determined by a double-label method in which nonspecific effects of the hormone were avoided. Isotope ratios of highly purified tRNASer species were measured following an in vivo labeling procedure which included a 7-day labeling period with [5-3H]orotic acid prior to, and a 6 h labeling with [6-14C]orotic acid from 42 h after the hormone injection. tRNASer (AGU,C) and tRNASer (UCU,C,A) were extensively purified by chromatography on benzoylated DEAE-cellulose in the presence and absence of Mg2+. In three separate labeling experiments the rate of tRNASer (UCU,C,A) synthesis was slightly but not significantly increased relative to the rate of tRNASer (AGU,C) synthesis during the period when vitellogenin was synthesized at a constant rate and the level of tRNASer continued to rise. The results suggest that mechanisms other than a differential rate of transcription are involved in the regulation of tRNASer levels in avian liver during vitellogenin induction.

Animals

Molecular characterization of vitellogenin and its receptor with CRISPR-based sgRNA validation in the legume pod borer, Maruca vitrata (Geyer) (Lepidoptera: Crambidae).

Maruca vitrata, the legume pod borer, causes yield losses of up to 80% in grain legumes. Increasing insecticide resistance and environmental concerns necessitate sustainable pest management alternatives. In the present study, the complete vitellogenin (Vg) coding sequence (CDS), a key reproductive gene involved in oogenesis and embryonic development, was cloned and molecularly characterised from M. vitrata. The assembled Vg CDS (∼5.3 kb) shared 99.04% sequence identity with the reported M. vitrata Vg sequence (MG799570.1). Phylogenetic analysis demonstrated close evolutionary association with related Lepidopteran species, while protein domain analysis identified three conserved domains, namely LPD_N, DUF1943, and VWD. Among these, the single exon-encoded LPD_N domain was selected as the target region for CRISPR/Cas9-mediated editing. Homology models of Vg and vitellogenin receptor (VgR) (Global Model Quality Estimation (GMQE): 0.58 and 0.51) showed a favourable interaction by protein-protein docking (score: -295.66). Three single-guide RNAs (sgRNAs) were designed, synthesised through in-vitro transcription, and evaluated using in vitro cleavage assays. sgRNA1 targeting the LPD_N domain and sgRNA2 targeting the signal peptide region exhibited efficient site-specific cleavage activity, whereas sgRNA3 failed to induce cleavage because of an unfavourable secondary structure that likely impaired Cas9-sgRNA complex formation. Overall, this study provides the first CRISPR-oriented functional characterisation and sgRNA validation of the M. vitrata Vg gene, together with structural characterisation of VgR and Vg-VgR interaction analysis, providing preliminary molecular resources for future CRISPR/Cas9 studies and supporting future embryo microinjection and heritable genome editing for sustainable management of M. vitrata.

CRISPR/Cas9

An estrogen receptor from Xenopus laevis liver possibly connected with vitellogenin synthesis.

This paper describes an estrogen receptor which is found in both the nucleus and cytoplasm of liver cells from male Xenopus laevis, and which seems to be involved in the induction of vitellogenin synthesis. It has a high affinity for estradiol (Kd = 0.5 x 10(-9) M), and the affinities of various steroids for the receptor correlate well with their ability to induce vitellogenin synthesis. It sediments at 3.5S at 0 degrees C in 0.5 M KCI. The rate of sedimentation is unaffected by incubation at 20 degrees C prior to centrifugation, but increases if the salt concentration is lowered to 0.1 M KCI or to zero. It has a Stokes radius of 2.6 nm and a molecular weight of approximately 40,000. The receptor is present at very low levels compared to other steroid target tissues (50--100 fold less than chick oviduct). The cytoplasm of a single hepatocyte contains 92 +/- 18 binding sites for estradiol, while each nucleus contains 99 +/- 19 sites.

Animals

Vitellogenin, lipid and carbohydrate metabolism during vitellogenesis and pregnancy, and after hormonal induction in the blenny Zoarces viviparus (L.).

1. Ovarian vitellogenic growth in Zoarces viviparus lasts about 2 months. Vitellogenesis is immediately followed by ovulation, fertilization and a pregnancy period of 4 months. Vitellogenin is observed in the blood during vitellogenesis, but declines during the first month of pregnancy. 2. The largest amount of liver lipid is found before vitellogenesis is initiated. During pregnancy the liver is depleted of lipid and glycogen, and total lipid and phospholipid is accumulating in the blood. 3. Estradiol treatment during pregnancy results in a dose-dependent increase in vitellogenin and lipids of the blood. 4. In late pregnancy, birth can be provoked with progesterone alone, or with combined progesterone and estradiol treatment.

Animals

Physical and chemical characterization of vitellogenin from the hemolymph and eggs of the tobacco hornworm, Manduca sexta.

1. Vitellogenin has been purified from mature eggs and the hemolymph of adult females of Manduca sexta by a combination of gel permeation chromatography and sodium bromide density gradient centrifugation. 2. It has a molecular weight of 2.6 x 10(5) and is a glycolipoprotein containing approx 11% lipids and 3% carbohydrates. 3. The carbohydrate moiety is comprised entirely of mannose and N-acetyl glucosamine. 4. Two polypeptide chains are present with molecular weights of 1.8 x 10(5) and 5.0 x 10(4). 5. Partial proteolytic hydrolysis of vitellogenin resulted in the degradation of the large polypeptide but did not affect the small one, suggesting that the small polypeptide is located in the interior of the particle. 6. The proteolytic hydrolysis products of the large polypeptide differed from one another by approx 12.5 x 10(3) daltons.

Amino Acids

Dose response kinetics of serum vitellogenin, liver DNA, RNA, protein and lipid after induction by estradiol-17 beta in male flounders (Platichthys flesus L.).

1. Male flounders receiving 100 micrograms estradiol each second day were fully induced to vitellogenin synthesis within 11 days, while fishes given 5 micrograms doses continued to accumulate vitellogenin in the serum at a progressive rate through 17 days. 2. Liver DNA per unit fish remained constant, while RNA per unit fish in flounders given 100 and 5 micrograms doses attained values 80 and 25% respectively, above the values found in control animals. 3. Liver RNA per unit DNA increased at maximal rate within 6 days in fishes receiving 100 micrograms doses. RNA synthesis continued at a progressive rate through 17 days in fishes given 5 micrograms doses of estradiol. 4. Liver protein per unit DNA elevated at a plateau 60% above control within 6 days with 100 micrograms doses. Doses of 5 micrograms had only little effect on liver protein. 5. Estradiol had a lipogenic effect on the liver. Cellular lipid rose 120 and 60% above control after treatment with 100 and 5 micrograms respectively. 6. Liver dry weight per unit DNA increased 60 and 55% above control with 100 and 5 micrograms doses respectively. Cellular hypertrophy in fishes receiving the smaller dose was primarily associated with an increase in lipid concentration, while protein and lipid contributed almost equally to cellular growth in fishes receiving the high dose.

Animals

Coordination of ribosome content and polysome formation during estradiol stimulation of vitellogenin synthesis in immature male chick livers.

To elucidate the mechanisms by which protein synthesis is affected by estradiol, we characterized cockerel liver polysomal profiles during hormone induction and withdrawal. We describe a method for isolating intact polysomes which results in preparations that are stable even after storage in solution at 10 degrees for 16 hr. In addition, our procedure eliminates the necessity for starving animals prior to experiments. Recovery of radioactive polysomes indicated that yield is about 90% and that our polysomal preparations appear to represent polysome distribution in vivo. Using this approach we show that estradiol injection stimulates ribosome content 6-fold and that formation of polysomes is coincident with the induction of vitellogenin synthesis. We also demonstrate that the size and number of polysomes increase and decrease in a coordinated fashion with the rate of vitellogenin synthesis. The kinetics of ribosome synthesis and the fact that at least 80% of the newly synthesized ribosomes are directly recruited into polysomes indicate that ribosomes might be limiting the rate of protein synthesis during the stimulatory phase of the hormone cycle.

Animals

Decrease in functional albumin mRNA during estrogen-induced vitellogenin biosynthesis in avian liver.

Translation of rooster liver RNA in a wheat germ extract is shown to yield albumin as one of the cell-free products. Quantitation of albumin mRNA by the translation assay indicates that functional albumin mRNA represents 10% of total liver mRNA activity in control roosters. After estrogen administration, this level decreases in a continuous fashion until functional albumin mRNA represents 5% of total mRNA activity at 12 days. This decrease in functional albumin mRNA was correlated with several parameters of vitellogenin induction. Functional vitellogenin mRNA increases to a maximum at 4 days after hormone treatment and returns to control levels by 12 days. A similar pattern is seen for the hormone-stimulated increase in total mRNA activity. The decrease in functional albumin mRNA, therefore, persists after the vitellogenic response of the liver has been completed. These results suggest that the decrease in hepatic albumin synthesis after hormone treatment is due to an estrogen-mediated decrease in the content of albumin mRNA.

Albumins

In vitro transcription of vitellogenin sequences on chick liver chromatin.

The in vitro transcription of chick liver chromatin before and after estrogen treatment was studied. Transcription was by endogenous as well as homologous exogenous RNA polymerase II and the products were analyzed for size and specific vitellogenin sequences. Quantitatively more RNA was synthesized from chromatin of 24 h estrogen-treated (E 24) chicks than from that of untreated chicks. In either case the size of transcribed RNA ranged from 5S to larger than 28S and most was between 5S and 18S. When a fraction enriched in estrogen receptor (E-Rec) complex was added to chromatin from untreated chicks, a dramatic shift of the RNA transcribed into heavier regions occurred. Analysis of RNA transcripts by hybridization to cDNAvit showed an equal number of sequences transcribed from E 24 chromatin and control; however, 13 times more specific sequences were transcribed in the presence of E-Rec complex. The results indicate the E-Rec complex exerts a regulatory function in the specific transcription of the vitellogenin gene.

Animals

Size, complexity and abundance of a specific poly(A)-containing RNA of liver from male Xenopus induced to vitellogenin synthesis by estrogen.

Estrogen treatment of Xenopus males leads to the appearance of a new species of poly (A)-containing RNA in the liver, at a stage when large amounts of the estrogen-induced yolk precursor protein, vitellogenin, is produced. This estrogen-induced RNA sediments at 28 S and migrates on gels in aqueous solution with an apparent molecular weight of 2.0 X 10(6). Contour length measurements under denaturing conditions in the electron microscope reveal a molecular weight of 2.34 X 10(6) compared to the mouse 28-S rRNA. Labeling experiments show that the estrogen-induced RNA has a stability than the average liver poly(A)-containing RNA and represents 10-20% of the poly(a)-containing RNA in the cytoplasm after 24 h of labeling. Hybridization of complementary DNA, synthesized on the isolated estrogen-induced RNA, with its template suggests a complexity corresponding to a single species of poly(A)-containing RNA of such a high molecular weight. Hybridization of the complementary DNA with cytoplasmic poly (A)-containing RNA from estrogen-treated Xenopus males and control toads show that the estrogen-induced RNA constitutes 12-15% of all cytoplasmic poly(A)-containing RNA, and is at least 2000-fold less abundant in untreated males. Size, complexity and abundance of the estrogen-induced RNA are characteristics expected for a mRNA coding for vitellogenin.

Animals