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G Ab

Publications and source records attributed to G Ab.

At least 55 records · Page 3Linked to original sources
PubMed1986

Estradiol-dependent transcription initiation upstream from the chicken apoVLDLII gene coding for the very-low-density apolipoprotein II.

We have investigated RNAs originating from the 5'-flanking region of the chicken very-low-density apolipoprotein II (apoVLDLII) gene. S1 nuclease mapping and primer extension experiments revealed two minor upstream transcription start points located 1105 and 1530 nucleotides in front of the apoVLDLII gene. Transcription starting at these points is dependent upon estradiol as is transcription from the major start points. The transcripts are polyadenylated, but are not detectable in polysomes. Run-on assays indicated that the low concentration of the upstream initiated transcripts is due both to low transcription levels and to low transcript stability. The sequence around the upstream start points does not show strong homologies with consensus sequences of promoters for eukaryotic protein encoding genes. Nevertheless, the upstream sequences are transcribed in vivo by RNA polymerase II.

Animals↗
PubMed1985

Expression-linked demethylation of 5-methylcytosines in the chicken vitellogenin gene region.

We have studied the methylation status of the estradiol-controlled chicken vitellogenin (Vtg) gene, which is expressed in the liver. A 30-kb region was investigated, containing 17 HpaII and 18 HhaI sites, of which 21 are in the 22-kb gene. Of these 21 sites, 9 were found to be demethylated in laying-hen liver relative to immature chicken liver. Outside the transcribed region, only one site was found to be relatively undermethylated in laying-hen liver. This site, at 0.6 kb in front of the gene, is, as shown earlier, also demethylated in rooster or immature chicken liver upon primary hormone stimulation, as well as in the non-expressing estradiol target organ oviduct. In this respect, this site sharply contrasts with those in the transcribed region, which appear to become demethylated only upon prolonged transcription of the gene.

5-Methylcytosine↗
PubMed1985

Nuclease-hypersensitive sites in chromatin of the estrogen-inducible apoVLDL II gene of chicken.

DNAseI-hypersensitive sites were localized in apoVLDL II chromatin from chicken. In the liver two sites at 1.75 and 1.0 kb upstream from the cap-site are present before the gene is activated. After induction by estradiol a number of additional sites appear, three in the promotor region of the gene, one within the coding region and two behind the poly-A signal. These sites disappear when the expression of the gene is shut off upon estradiol withdrawal. All sites appear to be tissue-specific in that they are not found in other tissues of the rooster. However, in oviduct of the laying hen we find a hypersensitive site at 1.6 kb in front of the gene.

Animals↗
PubMed1985

Estrogen receptor in chicken oviduct: receptor dissociation kinetics and transformation.

Cytosolic and nuclear estrogen receptor forms of chicken oviduct have been studied by (1) measuring hormone dissociation kinetics and by (2) sucrose density gradient analysis on high salt gradients. Estradiol dissociates from the receptor in chicken oviduct cytosol at 22 degrees C following a two-phase exponential process. The fraction of receptor with a fast dissociation rate (k = 120 X 10(-3) min-1) decreases as a function of the pre-incubation at 22 degrees C; after prolonged pre-incubation only the slowly dissociating (k = 12.3 X 10(-3) min-1) form remains. Dissociation of moxestrol, a synthetic estrogen with a higher affinity, from the cytosol receptor at 30 degrees C is similar, showing a transition of a fast dissociating form (k = 120 X 10(-3) min-1) to a slowly dissociating form (k = 7.6 X 10(-3) min-1) as a result of pre-incubation at 30 degrees C. A concomitant temperature-dependent shift of the estrogen receptor from a 4.8 S to a 6.1 S form was observed with moxestrol but not with estradiol as a ligand. Sodium molybdate (20 mM) and NaSCN (400 mM) inhibit the temperature-dependent increase in sedimentation coefficient, but molybdate allows the formation of a receptor form which shows intermediary dissociation kinetics. Estrogen receptor, precipitated with ammonium sulfate (0-35%) shows monophasic dissociation kinetics of estradiol (k = 39.5 X 10(-3) min-1) and for moxestrol (k = 10.8 X 10(-3) min-1), suggesting full receptor activation only with moxestrol as a ligand. Moxestrol-receptor complexes obtained by ammonium sulfate precipitation sediment at 0 degree C at 4.8 S. Only after subsequent incubation at 30 degrees C a shift from 4.8 S to 5.9 S is observed, suggesting that the formation of the slowly dissociating form of the receptor may precede the formation of a stable transformed receptor complex. The nuclear estrogen receptor with estradiol as a ligand shows biphasic dissociation kinetics at 22 degrees C (k = 70 X 10(-3) min-1; k = 14.0 X 10(-3) min-1). The ratio of both components (1:1) does not change after preincubation of the nuclear receptor extract at 22 degrees C. Moxestrol dissociates from the nuclear receptor at 30 degrees C monophasically with a slow rate (k = 6.1 X 10(-3) min-1), suggesting that it is extracted as an activated hormone-receptor complex.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Amino acid sequence of phosvitin derived from the nucleotide sequence of part of the chicken vitellogenin gene.

The amino acid sequence of the egg yolk storage protein phosvitin has been deduced from the nucleotide sequence of part of the chicken vitellogenin gene. Of the phosvitin sequence, 210 amino acids including the N-terminal residue are contained on one large exon, whereas the remaining six amino acids are encoded on the next exon. Phosvitin contains a core region of 99 amino acids, consisting of 80 serines, grouped in runs of maximally 14 residues interspersed by arginines, lysines, and asparagines. The serines of the core region are encoded by AGC and AGT codons exclusively and the arginines by AGA and AGG, which results in a continuous stretch of 99 codons with adenine in the first position. The N-terminal quarter of the phosvitin sequence contains 16 serines grouped in a cluster with alanines and threonines and coded mainly by TCX triplets. The C-terminal part includes 27 serines, preferentially coded by AGC and AGT, 13 histidine residues, and the sequence ...Asn-Gly-Ser... at which the carbohydrate moiety of phosvitin is attached. Heteroduplex formation between cloned DNAs from chicken and Xenopus vitellogenin genes shows that the phosvitin sequence contains a stretch of highly conserved sequence.

Amino Acid Sequence↗
PubMed1984

Interaction of calf uterine estrogen receptors with chicken target cell nuclei.

The calf uterine estrogen receptor (ER) was used to study the capacity and the characteristics of the acceptor sites in chicken target cell nuclei. The temperature-activated ER is bound at 0 degrees C with a high affinity to all chicken cell nuclei tested (Kd = 0.4-1.0 nM). The nuclear binding displayed tissue specificity: oviduct greater than liver, heart greater than spleen greater than erythrocytes and was salt-dependent. ER binding to liver nuclei measured in 0.15 M KCl varied between 3000 and 6000 acceptor sites per nucleus. Liver nuclei isolated from estrogen-treated cockerels showed a 2-fold lower binding capacity than nuclei from non-treated chickens. When nuclei were incubated with [3H]ER from embryo liver and increasing concentrations of uterine non-radioactive-ER a progressive inhibition of the binding of the liver ER was found. These experiments suggest that liver and uterine ER compete for a common acceptor site. Liver nuclei charged in vitro with calf uterine ER were digested at 0 degree C with DNAase I and micrococcal nuclease. Both enzymes excised the ER in the form of a chromatin-ER complex. A considerable portion was associated with nucleosomal subunits and a minor fraction was associated with a nuclease-sensitive, protein-poor fraction of the chromatin.

Animals↗
PubMed1983

The nucleotide sequence of the chicken apo very low density lipoprotein II gene.

The nucleotide sequence of the chicken apo Very Low Density Lipoprotein II (apoVLDL II) gene and the regions immediately flanking the gene was determined. Nuclease S1 mapping showed that transcription is initiated at two sites, about 11 bp apart, of which the one lying downstream is used preferentially. Comparison of the 2918-base pair gene sequence with the earlier determined cDNA sequence [Wieringa et al. (1981) Nucleic Acids Research 9, 489-501] enabled us to identify the four exons which are 38 (or 49), 100, 160 and 358 bp long. One of the intron-exon junctions has an unusual sequence. In the 5' flanking region several palindromic sequences are observed. Sequences near the 5' and 3' ends show homologies with the ovalbumin gene.

Animals↗
PubMed1983

Methylation of the chicken vitellogenin gene: influence of estradiol administration.

The degree of methylation of the chicken vitellogenin gene has been investigated. Upon induction by administration of estradiol to a rooster, methyl groups at specific sites near the 5'-end of the gene are eliminated. The process of demethylation is slower than the activation of the gene. Demethylation is therefore probably not a prerequisite to gene transcription. At least two other sites in the coding region of the gene are methylated in the liver of estrogenized roosters, but not in the liver of a laying hen, where the gene is naturally active.

Aging↗
PubMed1983

Sequence homologies within the 5' end region of the estrogen-controlled vitellogenin gene in Xenopus and chicken.

In oviparous vertebrates vitellogenin, the precursor of the major yolk proteins, is synthesized in the liver of mature females under the control of estrogen. We have established the organization and primary structure of the 5' end region of the Xenopus laevis vitellogenin A2 gene and of the major chicken vitellogenin gene. The first three homologous exons have exactly the same length in both species, namely 53, 21 and 152 nucleotides, and present an overall sequence homology of 60%. In both species, the 5'-non-coding region of the vitellogenin mRNA measures only 13 nucleotides, nine of which are conserved. In contrast, the corresponding introns of the Xenopus and the chicken vitellogenin gene show no significant sequence homology. Within the 500 nucleotides preceding the 5' end of the genes, at least six blocks with sequence homologies of greater than 70% were detected. It remains to be demonstrated which of these conserved sequences, if any, are involved in the hormone-regulated expression of the vitellogenin genes.

Amino Acid Sequence↗
PubMed1982

Estrogen receptor in avian embryo and adult liver: estrogen receptor activation and dissociation kinetics of estradiol, ethynylestradiol, and moxestrol.

Estrogen receptor-enriched fractions from cockerel and embryo liver cytosol were obtained by precipitation at 0--35% ammonium sulfate saturation. At low ionic strength conditions, the embryo receptor sediments in sucrose density gradients mainly as an 8S entity. The cockerel receptor, however, sediments at 4.9S, unless an inhibitor of thiol proteases, iodoacetate, is included in the isolation medium. Moreover, the affinity of the cockerel receptor for moxestrol is doubled in the presence of iodoacetate and equals that of the embryo receptor (Kd = 1.4--1.8 x 10(-10) M). We conclude that thiol cathepsins from cockerel liver cause proteolytic degradation of the estrogen receptor. At temperatures between 0--28 C, the dissociations of moxestrol, ethynylestradiol, and estradiol follow monophasic kinetics. At 28 C, the half-times for the moxestrol-, ethynylestradiol-, and estradiol-receptor complexes are 65, 11, and 6 min, respectively. The chaotropic salt, NaSCN, reduces 6-fold the half-time of the moxestrol-receptor complex at 28 C (t 1/2 = 10 min). In 0.15 M KCl, the estrogen-receptor complex from embryo liver sediments at 4S. Incubation at 28 C, before the sucrose gradient analysis at 0 C, does not change the sedimentation coefficient. Sucrose gradient centrifugation carried out at 20 C results in the transformation to a 5S form of the moxestrol- as well as the estradiol-receptor complex. Our findings suggest that the estrogen receptors in the cytosol of avian liver and mammalian reproductive tissues are very similar. From both tissues, the native 8--10S form is extracted, and the receptors are transformed into the 5S form upon incubation with hormone at 20--30 C.

Animals↗
PubMed1981

Structure of the chicken apo very low density lipoprotein II gene.

We describe two cloned genomic DNA fragments, both bearing the entire apo very low density lipoprotein II gene. Electron microscopy and restriction enzyme mapping showed that this gene is split into at least four coding sequences by three or more intervening sequences. A very short exon at the 5'-end of the gene is separated by a 1.5-kilobase intron from the second exon, which codes for the AUG initiation codon of the mRNA.

Animals↗
PubMed1981

Estradiol-induced vitellogenin synthesis in duck liver.

We have studied the induction of vitellogenin by estradiol in duck liver. From the accumulation of vitellogenin in blood plasma we calculated that the rate of vitellogenin synthesis increases linearly with time for about 4 days after estradiol administration. Vitellogenin from chicken and duck cross-react immunologically and their mRNAs show only 7% sequence divergence. We could therefore determine vitellogenin mRNA content of duck liver using chicken vitellogenin cDNA as a hybridization probe. The number of vitellogenin mRNA molecules per hepatocyte increases from less than one in normal duck liver to 18 000 at 4 days after estradiol injection. The rate of vitellogenin synthesis in vivo is roughly proportional to vitellogenin mRNA content, although the data suggest a somewhat enhanced translation of vitellogenin mRNA at later times after hormone administration. Vitellogenin mRNA levels had returned to control values after 4 weeks after hormone administration. In the first 11 h after secondary administration of hormone vitellogenin mRNA accumulates at an only slightly higher rate than is observed after primary hormonal stimulation.

Animals↗
PubMed1981

Electron microscopic analysis of transcription of a ribosomal RNA operon of E. coli.

Transcription in vitro of the E. coli ribosomal RNA operon, rrnE, was analysed by electron microscopy. The transcription initiation sites of the two rrnE promoters in tandem, P1 and P2, were mapped and the transcription from both sites was compared. The first and the second transcription initiation site are about equally used when all nucleotides are present at 200 microM. Lowering the concentration of the second promoter's start nucleotide CTP to 3 microM reduces the use of the P2 site sharply. At all CTP concentrations used the nascent RNA chains from P1 are in the average longer than those from P2 after a fixed transcription time. Most probably, this difference is caused by a longer average interval before formation of the productive complex with the second promoter.

Base Sequence↗
PubMed1981

The nucleotide sequence of the very low density lipoprotein II mRNA from chicken.

The nucleotide sequence of an almost complete, double-stranded cDNA of chicken Very Low Density Lipoprotein II mRNA, carried in recombinant plasmid pVLDLII 3.33 (Wieringa et al., 1979, 7: 2147-2163) is presented. A stretch of 318 nucleotides codes for the pre-VLDLII polypeptide, which consists of a 24 amino acids signal and a 82 amino acids secreted protein. The coding stretch is flanked by 57 nucleotides in the 5'-leader sequence of the mRNA, and 258 nucleotides in the 3'-non-coding region. Hypothetical self-complementary structures of parts of the mRNA are presented.

Animals↗
PubMed1981

A mutation in the RNA polymerase beta' subunit causing depressed ribosomal RNA synthesis in Escherichia coli.

Macromolecular synthesis in an Escherichia coli mutant with a temperature-sensitive beta' subunit of RNA polymerase was analysed. At the non-permissive temperature ribosomal RNA synthesis is strongly reduced while messenger RNA synthesis is affected to only a slightly extent. The overall protein synthesis is only slightly affected. We conclude that the beta' subunit is involved in promoter recognition and plays a role in transcriptional selectivity.

DNA-Directed RNA Polymerases↗
PubMed1981

Translation in vivo and in vitro of mRNAs coding for vitellogenin, serum albumin and very-low-density lipoprotein II from chicken liver. A difference in translational efficiency.

Characterisation of polysomes from estrogenized chicken liver revealed that very-low-density lipoprotein II (VLDLII), serum albumin and vitellogenin mRNAs are differently packed with ribosomes during translation in vivo. Tne ribosome density per number of nucleotides is high for VLDLII mRNA, intermediate for serum albumin mRNA and low for vitellogenin mRNA. This difference in ribosomal load is maintained throughout the period of hormone effect. The differential utilisation observed for vitellogenin and VLDLII mRNAs partly explains the large difference in molar production rate between these yolk protein precursors. Translation properties and efficiency of the three hepatic mRNAs were also compared in the mRNA-depleted reticulocyte lysate. Elongation of the nascent chains for vitellogenin and serum albumin proceeded in a discontinuous fashion. Initiation in vitro was studied at varying ionic strengths, in the presence of aurintricarboxylic acid, and at suboptimal hemin concentrations. VLDLII mRNA expression is by far the most resistant to 7-methylguanosine 5'-triphosphate (m7GTP) and high salt concentrations, vitellogenin mRNA the least. This behaviour resembles the differential utilisation of the mRNAs in vivo. The putative structural basis of these differences is discussed.

Animals↗
PubMed1981

Enhancement of ribosomal ribonucleic acid synthesis by deoxyribonucleic acid gyrase activity in Escherichia coli.

The effect of the deoxyribonucleic acid (DNA) gyrase inhibitors coumermycin A1, novobiocin, and oxolinic acid on ribonucleic acid (RNA) synthesis in Escherichia coli was studied in vivo and in vitro. Preferential inhibition of ribosomal RNA (rRNA) synthesis was observed. No effect of oxolinic acid and coumermycin on rRNA synthesis was seen in mutants having a DNA gyrase which is resistant to these inhibitors. In a temperature-sensitive DNA gyrase mutant rRNA synthesis was decreased at nonpermissive temperatures. Thus, a functional DNA gyrase is required for rRNA synthesis. Purified DNA gyrase had no effect on rRNA synthesis in a purified system. However, DNA gyrase does show preferential stimulation of rRNA synthesis in a system supplemented with other proteins. Apparently, DNA gyrase stimulation of rRNA synthesis requires another protein.

Aminocoumarins↗