Effects of estrogen and progesterone on transcription, chromatin and ovalbumin gene expression in the chick oviduct

Molybdate and the molecular properties of the vervet monkey estrogen receptor

The Vervet monkey (Cercopithecus aethiops pygerythrus) uterine estrogen receptor was partially characterised. The effect of the molybdate oxyanion on various molecular properties of the receptor was investigated. Molybdate appeared to affect the subunit structure and apparent heterogeneity of the receptor. Anion exchange chromatography of uterine cytosols yielded two ligand binding subunits in a 1:1 ratio in the absence of sodium molybdate, while only a single labelled complex could be demonstrated in cytosols prepared in molybdate containing buffers. Chromatofocussing of the nonstabilized cytosols revealed substantial receptor heterogeneity (7 peaks) while a much simpler pattern (2 peaks) could be observed in the presence of the molybdate. Likewise, iso-electric focussing of labelled cytosols on agarose gels yielded at least 3 high affinity binding components (pI:6.8, 6.2, 5.9) in the absence and only one major band in the presence of sodium molybdate (pI 5.9).

Correlation in isolated nuclei of template-engaged RNA polymerase II, ovalbumin mRNA synthesis, and estrogen receptor concentrations

Template-engaged and total RNA polymerase II molecules were quantitated in isolated nuclei at various stages of estrogen withdrawal and secondary stimulation by using [3H]amanitin titration assays. Estrogen receptors, RNA transcriptional activity, and ovalbumin mRNA were also measured, and comparisons were made between these parameters to determine whether any significant correlations exist. In isolated nuclei, the highest positive correlations existed between template-engaged RNA polymerase II, ovalbumin mRNA synthesis in vitro, and estrogen receptor concentration. Interestingly, restimulation of estrogen-withdrawn chicks results in replenishment of RNA polymerase II activity to prewithdrawal levels within 4 h; however, the recovery of the numbers of template-engaged polymerase II molecules, ovalbumin gene transcription, and nuclear receptor binding lags behind. These findings suggest that the estrogen effect on RNA polymerase activity is more rapid than the increase in template-engaged RNA polymerase II and ovalbumin-specific gene transcription. The excellent correlation that exists between nuclear estrogen receptor concentrations, template-engaged RNA polymerase II, and ovalbumin gene transcription strongly supports the hypothesis that estrogen receptors mediate RNA polymerase II binding to sequences associated with preferential transcription of the ovalbumin gene.

Effects of serial hormone treatments on egg white protein synthesis. Further evidence of translational regulation

The administration of either progesterone or estrogen to withdrawn chicks several hours after a first dose of estrogen affected ovalbumin synthesis differently than its mRNA levels [S. S. Seaver (1981) J. steroid Biochem. 14, 949-957]. This suggested that the hormones were regulating the translation of ovalbumin directly. In this paper we report that serial hormone treatments also affect the rates of synthesis of two other egg white proteins, conalbumin and ovomucoid. When progesterone was administered 4 h after estrogen, conalbumin synthesis decreased. When either progesterone or a second dose of estrogen was administered 12 h after the first dose of estrogen, conalbumin synthesis increased. Serial hormone treatments did not always affect all three proteins similarly. At later times, administering progesterone after estrogen decreased ovomucoid synthesis but did not affect conalbumin or ovalbumin synthesis. To determine if the serial hormone treatments affect egg white protein mRNA's in a similar way, changes in ovalbumin and conalbumin mRNA levels were quantified in a rabbit reticulocyte cell-free translation system and were compared to changes in ovalbumin and conalbumin synthesis as measured in chick oviduct tissue minces. When serial hormone treatments were 12 h apart, ovalbumin and conalbumin synthesis was 50-300% higher than that predicted by the changes in ovalbumin or conalbumin mRNA levels. This is further evidence that translation of both conalbumin mRNA and ovalbumin mRNA is directly regulated by steroid hormones.

Lack of an effect of estrogen on endogenous RNA polymerase II in guinea pig brain

An early action of estrogen in peripheral target tissues is to increase endogenous RNA polymerase II activity which precedes changes in protein synthesis. Previous reports have indicated that estrogen causes a similar increase in polymerase activity in rat brain regions containing high affinity receptors for this hormone. The present series of experiments was designed to test whether a similar action of estrogen on polymerase activity occurs in guinea pig brain, with the expectation being that this enzyme might prove to be a useful marker for the early actions of estrogen. Injections of 25 or 100 micrograms estradiol-17 beta in an ethanol-saline vehicle failed to induce significant changes in polymerase II activity in the basal hypothalamus, preoptic area-septum or cortex 1, 2, 6, 13 or 24 h after hormone administration. It is concluded that the modification of RNA polymerase II activity by estrogen is not a good marker for estrogen action in the brain. This may be due to the intrinsic heterogeneity of the tissue resulting possibly in (1) increased activity in some cells and decreased activity in other cells with no net change in overall polymerase activity after estrogen treatment (2) only a small percentage of the cells responding to the steroid with altered polymerase activity with this change not detectable when whole tissue is measured or (3) only a few genes within the cells being altered in transcription by the steroid.

The effect of progesterone on RNA polymerases in the rat uterus

The effect of progesterone on transcription was investigated in the uterus of the ovariectomized rat. Progesterone rapidly depressed both RNA polymerase A and B activities for up to 6 h after steroid administration. Both enzyme activities returned to control values 24 h after steroid treatment. In contrast, in the estrogen-primed rat uterus, progesterone was capable of stimulating RNA polymerase B activity 30 min after hormone treatment. The cellular entities or mechanisms which progesterone uses to alter transcription in cell nucleus remain to be determined.

Interaction of the chick oviduct progesterone receptor with deoxyribonucleic acid

The purified DNA binding component (receptor A) of the chick oviduct progesterone receptor has been analyzed for its ability to bind to the cloned ovalbumin gene and to plasmid DNA of various structural compositions. The rapid equilibrium filter adsorption assay of Riggs et al. [Riggs, A. D., Suzuki, H., & Bourgeois, S. (1970) J. Mol. Biol. 48, 67] has been used to demonstrate high affinity binding of the protein to DNA (Kdiss = 10(-10) M at 50 mM KCl, pH 7.2). Studies of association rates are consistent with equilibrium measurements (t 1/2 = 40-80 min). Association of purified receptor with DNA and the kinetics of the interaction have been verified independently by velocity sedimentation techniques. Direct binding assays were performed with the ovalbumin structural gene (cDNA), the entire natural ovalbumin gene containing seven intervening sequences, and various ovalbumin gene fragments coding for the 5' end of the nuclear precursor RNA, intron-exon junctions, and the 3'-noncoding region of the gene. No DNA-sequence specificity was identified for the binding of the receptor protein to any region of ovalbumin gene DNA. In contrast, the structural integrity of the DNA template greatly affected receptor binding. The poorest affinity was to supercoiled DNA and to blunt end, linear duplex gene fragments. The receptor bound saturably to DNA containing limited nicks but became nonsaturable as nicks were increased. Binding of the protein to double-stranded DNA increased susceptibility of the DNA to digestion by the enzyme S1, a single strand specific nuclease. On the basis of preferential receptor binding to single-stranded DNA, a possible mechanism involving DNA helix destabilization is discussed.

Commitment of chick oviduct tubular gland cells to produce ovalbumin mRNA during hormonal withdrawal and restimulation

Acute withdrawal of estrogen from chicks leads to a precipitous decline in egg white protein synthesis and egg white mRNAs in the oviduct. In this paper we explore the biochemical basis of this phenomenon as well as the capacity of the "withdrawn" tubular gland cells to be restimulated with steroid hormones. During withdrawal, the decline in ovalbumin mRNA was closely correlated with the decline in nuclear estrogen receptors. Within 2-3 d of estrogen removal a withdrawn state was established and then maintained, as defined by a 1,000-fold-lower level of ovalbumin mRNA and a 20-fold-lower level of nuclear estrogen receptors, relative to the estrogen-stimulated state. The number of active forms I and II RNA polymerases declined by 50% during this time. Histological examination of oviduct sections and cell suspensions, combined with measurements of DNA content, revealed that tubular gland cells persisted as a constant proportion of the cell population for 3 d after estrogen removal. Despite a 1,000-fold decrease in the content of ovalbumin mRNA, the ovalbumin gene remained preferentially sensitive to digestion by DNase I. When 3-d-withdrawn oviducts were restimulated with either estrogen or progesterone, in situ hybridization revealed that greater than or equal to 98% of the tubular gland cells contained ovalbumin mRNA. Induction by a suboptimal concentration of estrogen was correlated with a lower concentration of ovalbumin mRNA in all cells rather than fewer responsive cells.

Ovalbumin messenger ribonucleic acid accumulation in the chick oviduct during secondary stimulation: influence of combinations of steroid hormones and circannual rhythms

We have analyzed by hybridization the accumulation of ovalbumin mRNA after the administration of estrogen, progesterone, these two hormones together, or each hormone with testosterone to "withdrawn" chicks (chicks previously stimulated with estrogen but then withdrawn from the hormone). We were interested in determining if the time lag between hormone treatment and a significant increase in ovalbumin mRNA levels could be shortened. After every hormonal treatment we found that there was a 1.5-2.5-h lag period before a significant increase in ovalbumin mRNA levels. This lag period was not simply due to the slow delivery of the hormone to the oviduct. Nuclear estrogen receptor levels had plateaued by 1 h. Rather unexpectedly, the rate of ovalbumin mRNA accumulation after this lag period seemed to depend on the time of the year. Ovalbumin mRNA accumulated faster during the summer and early fall than during the winter and early spring. These seasonal differences were also observed in ovalbumin mRNA levels 24 h after hormone treatment. Such a circannual rhythm may help explain reported differences in the rate of ovalbumin mRNA accumulation during secondary stimulation.

Factors influencing association of glucocorticoid receptor-steroid complexes with nuclei, chromatin, and DNA: interpretation of binding data

Attempts to reconstruct, in a test tube, the steroid-hormone system of a responsive cell are fraught with enumerable difficulties. In this chapter I have attempted to point out some of the factors that affect receptor-steroid complexes and their interactions with acceptors. In most cases there is a quantitative influence of these factors on the level of steroid complex binding to acceptors. In some cases, selected experimental designs that neglect these factors and methods of presenting the observed data may lead to artifactual conclusions. Several of these problems should disappear when the prospect of pure receptor-steroid complexes [127, 147, 150, 181, 247, 248] becomes a common occurrence. Nevertheless much has already been learned about the interactions of complexes with acceptors, which in turn have been used to help formulate models of steroid-hormone action.

Estrogen withdrawal in chick oviduct. Characterization of RNA synthesized in isolated nuclei using a mercurated precursor

1. As a prerequisite for analyzing the effect of estrogen on transcription in chick oviduct, we describe suitable methods for the synthesis (under conditions restricting reinitiation), and isolation of RNA transcripts from oviduct nuclei in vitro, utilizing mercurated UTP (Hg-UTP) as an RNA precursor and chromatography on sulphydryl-Sepharose (SH-Sepharose) to recover mercurated RNA (Hg-RNA). The techniques described include treatment of Hg-RNA with p-hydroxymercuribenzoate, to improve the efficiency of binding to SH-Sepharose, and elution of Hg-RNA from SH-Sepharose after treatment with 60% formamide at 90 degrees C, to eliminate contamination by aggregated nucleic acid. 2. RNA synthesized by endogenous form B RNA polymerase (using either UTP or Hg-UTP as precursor) was recovered in nuclear lysates in the form of 30--85-S heterogeneous RNA . protein complexes, and after removal of protein, was 10--12 S in size. 3. The nature of RNA transcripts synthesized in vitro was examined by hybridization. More than 90% of the RNA was complementary to "unique" DNA sequences, and 50--60% of the hybridized RNA could be competed with homologous, steady-state nuclear RNA, indicating a significant degree with homologous, steady-state nuclear RNA, indicating a significant degree of homology between in vitro transcripts and in vivo RNA. The level of homology was similar whether RNA synthesis was performed in low salt, or in high salt in the presence of heparin. Possible reasons for only partial competition in these experiments are discussed. 4. Withdrawal of estrogen from chicks leads to a 50% reduction in endogenous RNA polymerase activities in nuclei within 48 h. Similar levels of competition with Hg-RNA transcripts for "unique" DNA were obtained using oviduct nuclear RNAs isolated before or after estrogen withdrawal, and even with liver nuclear RNA. Thus, in oviduct, those sequences present in primary transcripts, and analyzed under our experimental conditions, are present in different hormonal states and also in other chick tissues.

Developmental restrictions on hormone modulated gene transcription. II. Hormone induced interactions of RNA polymerase with chromatin

Chromatin-bound and soluble RNA polymerase subspecies have been isolated and fractionated by isoelectric focusing at various times (0, 6, 12 and 18 h) following auxin treatment of 4 day (responsive) and 8 day (unresponsive) soybean hypocotyls. Young 4 day seedlings displayed two well defined phases of auxin induced gene transcription. Phase I (6 h) evidenced the selective dissociation of many RNA polymerase subspecies from the chromatin complex which was accompanied by the retention of three class II enzymes. Phase II occurred after 12 h of treatment when the dissociated enzymes including some species which were soluble in the 0 h controls became re-associated with chromatin. These induced RNA polymerases may be responsible for the synthesis of auxin induced RNAs. In contrast, the unresponsive 8 day hypocotyl did not display two phases of auxin induction. Phase one, the dissociation of the chromatin bound enzymes, occurred at 12 h (compared to 6 h for the 4 day seedling) and was not followed by the later translocation of any soluble enzymes towards the chromatin complex. The results support earlier findings suggesting that the developmental "phasing out" of RNA polymerase subspecies limits the hormone induced growth response of this tissue and thus is regarded as an off switch for the transcription of such hormone controlled gene sequences.

Progesterone-regulated changes in transcriptional events in rabbit uterus

The role of steroid receptors in the early events of progesterone action was elucidated by examining the temporal relationship between the nuclear accumulation of progestin receptor and changes in activities of RNA polymerases I and II, as well as that of chromatin template in rabbit uterus. Following a 5-day estrogen pretreatment, the animals received an intravenous injection of progesterone (10 mg), after which they were killed at timed intervals. Nuclear progestin receptor level, as measured by an exchange assay, reached the peak value 30 min after hormone administration (11 600 to 46 600 sites/nucleus) and declined to the control levels by 4 h. Changes in the activities of RNA polymerase I and II did not follow identical time courses: polymerase I rose at 30 min and remained elevated for 2 h and then declined to about 75% of the pretreatment activity, whereas RNA polymerase II activity increased more rapidly (at 15 min), and was followed by a sharp decrease to about 50% of the initial value. Thereafter, the latter enzyme activity rose slowly and reached the pretreatment level within 12 h of progesterone administration. Early changes in chromatin template activity were similar to those in RNA polymerase I with a second rise by 8--10 h. The early inhibition of transcriptional events by progesterone may result from antiestrogenic properties of this steroid. Accumulation of nuclear progestin receptor occurs at a similar time to early changes in the transcriptional events suggesting a regulatory role for the hormone receptor complexes.

Initiation and elongation of polyribonucleotide chains on rat ventral-prostate chromatin transcribed by homologous ribonucleic acid polymerase B

The characteristics of initiation of RNA synthesis and the elongation of RNA chains on rat ventral-prostate chromatin by RNA polymerase B were investigated by two methods. 1. Initiation was carried out under low-salt conditions with three ribonucleoside triphosphates, and elongation was begun in the absence of reinitiation by the addition of the fourth ribonucleoside triphosphate and increasing the salt concentration. 2. Stable initiation complexes were formed by preincubation of enzyme with template at 37 degrees C, elongation was started by the addition of all four ribonucleoside triphosphates and reinitiation or spurious RNA synthesis was prevented by rifamycin AF/013. The latter method gave more reliable results. The dependence of those parameters on the androgenic status of the animal was studied. During the first 24h after castration, elongation was mainly affected, whereas after 72h a smaller number of initiation sites for RNA polymerase B on chromatin was evident. Considerable diurnal variations in the various parameters were observed. Changes in the relative concentrations of the chromatin-associated proteins were also observed after castration. In the rat ventral-prostate gland androgenic steroids may not only influence one stage of the transcriptional process, but may affect many factors involved in the control of gene expression.

RNA polymerase activities in isolated nuclei of guinea pig seminal vesicle epithelium: influence of castration and androgen administration

Nuclei from seminal vesicle epithelium of adult guinea pigs were isolated in hypertonic sucrose solution. The incorporation of [3H]UTP by the isolated nuclei into acid-precipitable products was studied. Incorporation required ATP, GTP, CTP, UTP, and Mg+2. It was inhibited by addition of actinomycin D, deoxyribonuclease, or pyrophosphate to the reaction mixture. Thus, incorporation of [3H]UTP by isolated nuclei had the same characteristics that have been demonstrated for the reactions catalyzed by nuclear RNA polymerases. Using alpha-amanitin as a metabolic tool, we established concentrations of (NH4)2SO4. Mg+2, and nucleotides that give maximum assayable activities of nuclear RNA polymerases I and II. When the activities of polymerases I and II were measured in isolated seminal vesicle nuclei of guinea pigs that had been castrated 4 days earlier, a marked decrease in activities was found relative to control values (nuclei from intact animals). No further decrease was found 8 days after castration. Diminished accessibility to the nuclear DNA template and a decrease in the concentration of RNA polymerase molecules seemed to be responsible for the observed effects of castration on activities of RNA polymerases. An increase in ribonuclease activity did not seem to be responsible for the effects of castration. Activities of the enzymes did not change 2, 3, or 4 hours after intraperitoneal injection (2 mg/kg body weight) of each of five different androgens. Similarly, a single intraperitoneal injection of testosterone did not restore enzyme activity of polymerade I or II at any time during the first 24-hour period after hormone administration.