mRNA complexity and egg white protein mRNA content in mature and hormone-withdrawn oviduct

Effects of Continuous Estradiol Administration by Polydimethylsiloxane and Paraffin Implants on Serum Hormone Levels and Uterine Responses

Since tonic elevated estrogen levels are associated with toxic responses, including tumor promotion, we investigated the effects of continuous estradiol (E2) administration by paraffin or polydimethylsiloxane (Silastic) implants on pituitary and uterine responses. Ovariectomized (OVEX) Sprague-Dawley rats implanted with low-dose (P1) or high-dose (P2) paraffin pellets showed initial high serum E2 levels that decayed rapidly. Silastic implants provided more constant pharmacological serum E2 levels during the 14 days of exposure. Rising serum LH and FSH levels in OVEX controls were suppressed by all E2 implants. Serum prolactin levels, low in OVEX controls, rose after implantation (P1 and P2) but decayed to control values by 14 days. Prolactin induced by pharmacological E2 levels initially rose, dropped by 72 hours, but again rose at later times. Uterine weight, low in OVEX controls, was increased by all implants. At later times, paraffin implants did not appear to release significant amounts of E2. However, removal of P2 implants from donors followed by transfer to new recipients stimulated uterine growth in recipients. All implants increased uterine DNA and RNA levels and the RNA/DNA ratio during the first 24–48 hours, followed by maintenance of elevated values. Poly(A)-containing RNA, isolated by oligo(dT) cellulose chromatography, comprised a constant percentage of RNA at all hormone levels and treatment times, suggesting a coupling of total RNA and poly(A)-containing RNA accumulation. Results are discussed in relation to the carcinogenic properties of estrogens, known to be correlated with continuous exposure to elevated estrogen levels.

Effects of steroid hormones on age-related expression and modulation of the lysozyme gene of the oviduct of Japanese quail

The expression of lysozyme gene in the oviduct of Japanese quail is age-dependent. Here we show that the expression of the gene is altered by three steroid hormones: 17beta-estradiol (E), progesterone (P) and glucocorticoid (dexamethasone, G), and their combinations E+P, E+G and P+G. We also show that the levels/affinities of transacting factors that bind to specific cis-acting elements in the promoter region of the gene change with age and after steroid administration. These factors are sequence-specific, age and steroid-dependent. It is proposed that administration of appropriate doses of steroid hormones after adulthood may extend the reproductive function and egg laying period in birds.

Inducibility of the avidin gene by progesterone is suppressed during estrogen-induced cytodifferentiation

We have studied epithelial differentiation of the chick oviduct as induced by diethylstilbestrol (DES) and 17 beta-estradiol (E2). The proportion of goblet cells in the oviduct was slightly higher after E2 than after DES treatment. Also avidin induction by progesterone was stronger following DES than E2 priming. In the estrogen pretreated oviduct epithelium, avidin expression was induced by progesterone in the surface epithelial cells, protodifferentiated gland cells and tubular gland cells, but not in goblet cells. During prolonged estrogen treatment, however, the inducibility of avidin by progesterone ceased in tubular gland cells but not in surface epithelial cells. The estrogen action on the expression of avidin could be explained by estrogen-induced terminal differentiation of the epithelial gland cells or by a direct effect of estrogen on the progesterone action, for instance interaction of estrogen receptor and progesterone receptor in the regulation of transcription.

Chick oviduct differentiation. The effect of estrogen and progesterone on the expression of progesterone receptor

Progesterone receptor (PR) is a marker of estrogen action. Its cellular appearance during estrogen (20 mg/kg i.m.)-induced differentiation of the immature chick oviduct was therefore studied by immunohistochemistry. PR was located in the epithelial, mesothelial, submucosal stromal and smooth muscle cells. Progesterone (20 mg/kg i.m.) caused an obvious decrease in PR immunoreactivity without inducing synthesis of progesterone-dependent avidin. Thus mere receptor occupation by ligand is not sufficient for this induction. This paper reports that the expression of PR in the mucosal stromal cell differs from that in other cell types. In the mucosal stromal cell PR was inducible, i.e., not shown without the action of estrogen. The formation of tubular glands did not commence before mucosal stromal cells expressed PR. It would seem that the mucosal stromal cells have a crucial role in mediating epithelial differentiation. The onset of differentiation was preceded by vascularization and invasion of mononuclear cells in the submucosa. It was conspicuous that the smooth muscle cells of arteries also contained PR.

Distribution of isoaccepting tRNAs and codons for proline and glycine in collagenous and noncollagenous chicken tissues

The relation between codon usage and tRNA content for proline and glycine, the major constituents of collagen, was studied in two tissues: the magnum of laying hen oviduct and the leg tendons of chick embryo where collagen is produced. Although the relative contents of tRNA(GCCGly) and tRNA(IGGPro) in tendons, as compared to magnum indicate a specialization of the tRNA population for collagen synthesis, the distribution of the preponderant codons in collagen mRNA is correlated but at a lesser extent to that of their cognate tRNAs.

Lysozyme gene specific transcription in isolated hen oviduct nuclei

1. Transcription from the chicken lysozyme gene domain and the density of RNA polymerase molecules was studied by incubating isolated hen oviduct nuclei in an in vitro transcription system with [alpha-32P]UTP and hybridizing the purified [32P]RNA with immobilized restriction fragments. 2. The labeled RNA hybridized most prominently to coding and flanking restriction fragments that contain repetitive sequences. 3. Relatively weak hybridization signals with a coding, single-copy, genomic fragment and cDNA fragments were detected using 5000 microCi [alpha-32P]UTP per ml of incubation mixture. 4. Flanking, non-repetitive fragments did not hybridize to the [32P]RNA. 5. The results show that transcription from repetitive sequences dominates over lysozyme gene specific transcription.

Gene regulation by steroid hormones

The location, orientation, and structure of the hormone regulatory elements (HRE) in nine hormonally modulated genes is described. Based on analysis of the contact points between the glucocorticoid receptor (GR) and the DNA double helix within the HREs, a model for the interaction is proposed in which a dimer of the receptor in head-to-head orientation binds to the inverted symmetry element of the HRE. The relationship between the regulatory elements for glucocorticoids and progesterone in the long terminal repeat region (LTR) of mouse mammary tumor virus (MMTV), and in the promoter region of the chicken lysozyme gene, indicates that the recognition mechanism for both receptors is similar but not identical. Curiously, the hormone ligand is not an absolute requirement for the GR to bind its HRE, though it influences the kinetics of the interaction. Other possible functions of the hormone in vivo are discussed, as well as the molecular mechanism responsible for transcriptional regulation after receptor binding to the HRE.

The effects of androgen on the transcription of specific genes in guinea pig seminal vesicle epithelium

Steroid hormones have been shown to have highly differential effects on the expression of abundant cell-specific protein genes in a multitude of model tissues. In rat seminal vesicle, for example, DNA clones representing two major secretory protein genes have been used to show that both of the genes are differentially regulated by androgen. In this paper, we have examined the effects of androgen on the transcription of two major secretory protein genes in guinea pig seminal vesicle epithelium. Nuclear run-off experiments were used to show that castration of the adult resulted in a 3-fold decrease in total transcription activity. Surprisingly, the decrease in total transcriptional activity was not reflected in a differential decrease in the transcriptional activity of the two major secretory protein genes. When the effects of castration on the transcriptional activity of the major secretory protein genes were compared to the effects on other genes, it was found that the transcriptional activity of each gene examined was decreased by the same magnitude as the major secretory protein genes. Similarly, the transcriptional activity of every gene examined increased by the same magnitude as the major secretory protein genes during hormone repletion of the castrated adult. Thus, in contrast to the differential effects of steroids on the transcription of abundant cell-specific proteins in many other steroid-dependent tissues, the transcription of major secretory proteins in guinea pig seminal vesicle epithelium appears to be regulated in parallel with many other genes. The generalized effects of androgen on transcriptional activity could account for the generalized effects of androgen on seminal vesicle epithelial cell structure and function.

Cloning of the chick hsp 90 cDNA in expression vector

A cDNA clone for the 90kDa heat-shock protein, which we have recently identified as a component of steroid hormone receptors in their heteromeric 8S form, was isolated by direct immunological screening of a chicken smooth muscle cDNA expression library, prepared in the expression plasmids pUC8 and pUC9. Using polyclonal and monoclonal antibodies against the 90kDa protein a colony was identified that reacted with both antibodies. Plasmid 9.11 (p9.11, approximately 1100 base pair insert) was found to hybrid-select mRNA for the 90kDa heat-shock protein. Northern blot analysis revealed that RNA isolated from various chicken tissues contain a single transcript of approximately 3 Kb hybridizing to a [32P]labelled cDNA probe made from p9.11. Heat-shock treatment of chick embryonic fibroblasts resulted in increased steady-state levels of a 3 Kb transcript in both poly A+ and poly A- RNA fractions. Southern blot analysis of chicken genomic DNA indicated that the cDNA hybridizes to a single copy sequence. Sequence data show that the p9.11 cDNA displays a high degree of homology with the 5' portion of yeast heat shock protein 90 cDNA.

The TGGCA-binding protein: a eukaryotic nuclear protein recognizing a symmetrical sequence on double-stranded linear DNA

Low salt extracts of chicken oviduct nuclei contain a DNA binding protein with high affinity for specific DNA sequences in the flanking regions of the chicken lysozyme gene. Two of the three binding sites found within a total of 11 kb upstream from the promoter are located only 92 bp apart from each other. Upon comparison of the DNA binding sites, the symmetrical consensus sequence 5'- TGGCANNNTGCCA -3' can be deduced as the protein recognition site. This sequence is the central part of 23 to 25 base pairs protected by the DNA binding protein from DNAase I digestion. A homologous binding activity can be detected in nuclei from several chicken tissues and from mouse liver.

Definition of the ovalbumin gene promoter by transfer of an ovalglobin fusion gene into cultured cells

In order to study the initiation of transcription from the ovalbumin gene promoter, we constructed a hybrid gene (ovalglobin) in which 753 bps of ovalbumin gene 5'-flanking sequence were joined to the chicken adult beta-globin gene. When transfected into HeLa S3 cells, ovalglobin gene transcription initiated at the ovalbumin gene cap site, as measured by S1 nuclease and primer extension analysis. Deletion of 5'-flanking sequences to position -95 had little effect on transcription; deletion to -77 reduced transcription to about 20% of the wild type level and deletion to -48 reduced the level to about 2%. A deletion to -24, removing the sequence TATATAT, abolished transcription entirely. Hormonal regulation of the ovalglobin gene was observed when primary oviduct cells were used as recipients for DNA transfection. Under these conditions, addition of progesterone increased the level of ovalglobin transcripts to more than 10 times the uninduced level.

Nuclease-hypersensitive sites in the chromatin domain of the chicken lysozyme gene

We have examined the chromatin structure of a 22 kilobase-pair chromosomal region containing the lysozyme gene in laying hen. Nuclease-hypersensitive sites were probed with DNAase I by using an indirect end-labeling technique. Eight DNAase I-hypersensitive sites could be mapped in the flanking regions of the gene in oviduct cells, in which the gene is expressed. The same sensitive sites were detected by utilization of an endogenous nuclease activity present in oviduct nuclei. Only one hypersensitive site was detected in the chromatin from erythrocytes, in which the gene is not expressed. The 3'-terminus of the lysozyme gene is highly exposed in nuclei from both tissues. Of special interest is the hypersensitive site at the 5'-terminus of the actively transcribed gene since it maps at the region of multiple initiation sites of transcription and the putative control regions of steroid hormones. DNAase I-hypersensitive chromatin structures also at a greater distance from the gene may take part in the control of gene expression.

Heterogeneous initiation regions for transcription of the chicken ovomucoid gene

We have identified the 5' termini of ovomucoid RNA transcripts isolated from estrogen stimulated chick oviduct by S1-nuclease mapping. Most of the ovomucoid RNA molecules (88-89%) are initiated at a predominant region which is positioned at about 30 basepairs downstream from a "TATATAT" sequence. However, there is at least one additional initiation region which accounts for 9% of the ovomucoid RNA transcripts. It is located at approximately 80 basepairs further upstream (5') from the major initiation region. DNA sequence data reveal that an AT-rich sequence resembling the "TATA" box is also present 30 nucleotides before this minor region. Our finding provides additional insight into the molecular mechanism involved in the transcription initiation of eucaryotic genes, and indicates that in vivo synthesis of mRNA may not require an absolute site for initiation of transcription.

5'-Terminal sequences of eucaryotic mRNA can be cloned with high efficiency

A method for cloning mRNAs has been used which results in a high yield of recombinants containing complete 5'-terminal mRNA sequences. It is not dependent on self-priming to generate double-stranded DNA and therefore the S1 nuclease digestion step is not required. Instead, the cDNA is dCMP-tailed at its 3'-end with terminal deoxynucleotidyl transferase (TdT). The synthesis of the second strand is primed by oligo(dG) hybridized to the 3'-tail. Double-stranded cDNA is subsequently tailed with dCTP and annealed to dGMP-tailed vector DNA. This approach overcomes the loss of the 5'-terminal mRNA sequences and the problem of artifacts which may be introduced into cloned cDNA sequences. Chicken lysozyme cDNA was cloned into pBR322 by this procedure with a transformation efficiency of 5 x 10(3) recombinant clones per ng of ds-cDNA. Sequence analysis revealed that at least nine out of nineteen randomly isolated plasmids contained the entire 5'-untranslated mRNA sequence. The data strongly support the conclusion that the 5'-untranslated region of the lysozyme mRNA is heterogeneous in length.

Heterogeneity of the 5' terminus of hen ovalbumin messenger ribonucleic acid

The 5'-terminal sequence of hen ovalbumin mRNA was investigated using a novel labeling method. Ovalbumin mRNA was purified by hybridization to complementary DNA coupled to cellulose. The mRNA thus purified was shown to be 97.9% pure by hybridization with plasmid DNA containing sequences to the messengers coding for conalbumin and ovomucoid, the next two most abundant messengers of oviduct. After digestion with RNase T1 and alkaline phosphatase, 5'-terminal capped oligonucleotides were selected by binding to anti-m7G-Sepharose. These were then labeled using RNA ligase and [5'-32P]pCp, separated by two-dimensional gel electrophoresis, and sequenced by partial digestion with base-specific ribonucleases. A nested set of three capped oligonucleotides was identified. Their structures and relative abundances were m7GpppAUACAG, 3% m7GpppACAUACAG, 61+; and m7GpppGUACAUACAG, 36%.

Hormone-responsive expression of an endogenous proviral gene of mouse mammary tumor virus after molecular cloning and gene transfer into cultured cells

A recombinant lambda phage containing mouse mammary tumor virus (MMTV) proviral DNA was isolated from a gene library constructed from GR mouse liver DNA. Restriction enzyme analyses reveal that the cloned molecule contains a copy of one of the GR endogenous MMTV proviruses flanked on both sides by 2--3 kb of mouse genomic DNA. In this report we have examined the expression of the cloned MMTV provirus after cotransfection with the herpes thymidine kinase (TK; ATP:thymidine 5'-phosphotransferase,, EC 2.7.1.21) gene and integration into mouse LTK- cells. Nine individual TK+ transformants were selected, and all were found to contain MMTV-transfected DNA. One of the TK+ transformants was chosen for further study. Total poly(A)-containing RNA was isolated from the cells, and liquid hybridization analyses with MMTV cDNA showed that it contained 0.02% MMTV-specific RNA. The sizes of the MMTV-specific species were determined and found to correspond to the 35S and 24S mRNAs synthesized in MMTV-infected cells. Glucocorticoid hormones have been shown to increase the concentration of MMTV RNA in virus-infected cultured cells. Therefore, we tested the effect of dexamethasone on the concentration of MMTV-specific RNA in cells transfected with the MMTV proviral DNA. The amount of MMTV-specific poly(A)-containing RNA found in the cells grown in the presence of hormone was 0.17%. Therefore, dexamethasone causes an 8-fold increase in the amount of MMTV-specific RNA in mouse cells containing several copies of a cloned and transfected MMTV proviral gene.

[Gene structure and gene expression. Chicken lysozyme gene]

In the chicken oviduct the synthesis of the egg-white proteins ovalbumin, conalbumin, ovomucoid and lysozyme is controlled by the female sex steroids. The steroid-controlled rate of synthesis of these proteins is closely correlated to the cellular concentration of the egg-white protein mRNAs. The accumulation of these mRNAs is achieved by a decreased rate of degradation and an increased rate of synthesis. To understand the molecular mechanism that regulates the expression of this group of genes we have isolated the lysozyme and ovomucoid gene by gene-cloning. The structure and expression of the lysozyme gene has been studied.

The ovalbumin gene family: hormonal control of X and Y gene transcription and mRNA accumulation

The ovalbumin gene family is composed of three genes, X, Y and ovalbumin, which are expressed in laying hen oviduct. We have analyzed the in vivo transcription products of X and Y genes and the effect of steroid hormones on their synthesis and accumulation. As in the case of ovalbumin, the complete gene transcripts and processing intermediates are present in the poly(A)+ RNA fraction. The mature RNAs are found in polysomes and are translated into proteins. The expression of X and Y genes is controlled by steroid hormones: X and Y RNAs are not detectable in oviducts from chicks withdrawn from estrogen stimulation, whereas in chicks stimulated with estrogen for 7 days, X RNA represents 0.3% and Y RNA 0.8% of ovalbumin mRNA. In laying hen, however, the levels of X and Y RNAs are about 2% of ovalbumin mRNA. After stimulation with other steroid hormones, alone or in combination, the level of X and Y RNA does not achieve that detected in laying hen. Progesterone has a much weaker effect on X RNA accumulation than on that of Y and ovalbumin mRNAs. Studies with isolated nuclei show that X and Y gene expression is regulated by hormones at the level of transcription. However, the differences observed between the transcription rates and the accumulation of X and Y mRNAs suggest that the expression of X and Y genes could also be controlled at the levels of RNA processing and/or mRNA stability.

Primary sequence of ovomucoid messenger RNA as determined from cloned complementary DNA

Ovomucoid messenger RNA (mRNAom) comprises approximately 8% of the total mRNA in the estrogen-stimulated oviduct. The recombinant plasmid pOM100 contained DNA complementary to the 3' end of mRNAom. DNA complementary to the 5' end of mRNAom was obtained from a partially purified preparation of mRNAom by polymerization by reverse transcriptase in the presence of a restriction fragment primer from pOM100. The complementary DNA mixture was amplified by molecular cloning using poly dG/dC tailing to form recombinant bacterial plasmids. Recombinant plasmids containing ovomucoid DNA sequences were selected by in situ hybridization to 32P-labeled pOM100 fragments. The longest plasmid containing ovomucoid DNA sequences was designated pOM502. The complete DNA sequence of both pOM100 and pOM502 was determined. The two plasmids appear to contain sequences complementary to the entire length of mRNAom. The nucleic acid sequence agrees with the known amino acid sequences for both ovomucoid and its N-terminal signal peptide. Highly homologous sequences occur in two regions that coincide with structural domains of the protein. Comparison of the sequence of mRNAom with that for other eucaryotic mRNAs allowed identification of possible functional regions in the mRNA molecule.

RNA synthesis in rabbit endometrial nuclei. Hormonal regulation of transcription of the uteroglobin gene

Endometrical nuclei, prepared from rabbits subjected to different hormonal treatments, were used for the cell-free synthesis of RNA. Optimal conditions for the incorporation of [3H]UMP into RNA are described, leading to the synthesis of relatively undegraded RNA molecules. Under these conditions there is virtually no initiation of new RNA chains in vitro, and RNA chain elongation is inhibited up to 60% by low concentrations of alpha-amanitin and up to 90% by actinomycin D. The synthesis of RNA is slightly inhibited in the presence of Hg-CTP and monothioglycerol, but newly synthesized mercurated RNA can be efficiently separated from endogenous RNA upon chromatography on sulfhydryl-Sepharose under stringent conditions. The RNA synthesized in vitro by endometrial nuclei from pseudopregnant rabbits contains RNA sequences transcribed from the uteroglobin gene, as demonstrated by hybridization to an excess of purified preuteroglobin cDNA. In endometrial cells from pseudopregnant animals the number of RNA polymerase II molecules transcribing the uteroglobin gene is 12-fold higher than in control animals, demonstrating that at least part of the hormonally induced accumulation of preuteroglobin mRNA is due to an increased rate of transcription of the uteroglobin gene.

Light-induced appearance of polysomal poly(A)-rich messenger RNA during greening of barley plants

Changes in polysomal poly(A)-rich mRNA during greening of etiolated barley plants were studied by the technique of cDNA-mRNa hybridization. Hybridizaiton data of the homologous reactions reveal that in etiolated as well as in greened shoots a complexity of 5 X 10(7) nucleotides or about 33000 different average-sized mRNAs are present. These are organized in different abundancy classes with 94% of the total complexicity present in each of the slowest reacting class representing rare messengers. Heterologous hybridizations indicate that 92% of all polysomal poly(A)-rich mRNAs in etiolated shoots are complementary to those of greened and 82% of 'green' poly(A)-rich mRNAs are complementary to white ones. It is shown that the abundant mRNA clases are essentially responsible for these differences. The prevalent classes making up 15% ('white') and 31% ('green') of the poly(A)-rich mRNA mass but comprising only a complexity of 1.8 X 10(4) and 2.1 X 10(4) nucleotides are identical to 50% with each other. Hybridization of isolated prevalent 'green' cDNA with whole 'white' poly(A)-rich mRNA indicates that the additionally appearing 50% prevalent green messengers must be regarded as green-specific, only present in polysomal poly(A)-rich mRNA after illumination. This conclusion is underlined by the hybridization of the 'green' cDNA with total polysomal RNa of etiolated shoots. Evidently appearance of these prevalent messengers in functional polysomes is not caused by a shift from poly(A)-free mRNA to poly(A)-rich mRNA. The results clearly demonstrate that light induces greening by turning on genes or influencing post-transcriptional processing to produce mature green-specific poly(A)-rich mRNA.

Post-transcriptional regulation of messenger abundance in rat liver and hepatoma

Saturation hybridisation with labelled single-copy DNA shows that polysomal poly(A)+ RNA of rat liver and of a minimum-deviation rat hepatoma cell-line (HTC) have similar total complexities and that few sequences are specific to either cell-type. Hybridisation kinetics of polysomal cDNAs with template and heterologous cell RNAs indicate that a proportion of liver messengers are at greatly reduced abundance in the hepatoma, but not the converse. Hybridisations using fractionated cDNAs enriched for abundant polysomal sequences confirm these findings: on average, abundant liver mRNAs are about 100-fold rarer in hepatoma, whereas abundant hepatoma mRNAs are only 5-fold rarer in liver. This pattern is also implied by cell-free translation of polysomal poly(A)+ RNAs. The reactions of total and fractionated polysomal cDNA probes with poly(A)+ nuclear RNA indicate that there is much less disparity in abundance of these sequences at nuclear level, implying that the differences arise, at least in part, post-transcriptionally. We interpret the altered mRNA abundances in the hepatoma in terms both of its decreased functional specialisation and its ability to proliferate.

Number and location of mouse mammary tumor virus proviral DNA in mouse DNA of normal tissue and of mammary tumors

The Southern DNA filter transfer technique was used to characterize the genomic location of the mouse mammary tumor proviral DNA in different inbred strains of mice. Two of the strains (C3H and CBA) arose from a cross of a Bagg albino (BALB/c) mouse and a DBA mouse. The mouse mammary tumor virus-containing restriction enzyme DNA fragments of these strains had similar patterns, suggesting that the proviruses of these mice are in similar genomic locations. Conversely, the pattern arising from the DNA of the GR mouse, a strain genetically unrelated to the others, appeared different, suggesting that its mouse mammary tumor proviruses are located in different genomic sites. The structure of another gene, that coding for beta-globin, was also compared. The mice strains which we studied can be categorized into two classes, expressing either one or two beta-globin proteins. The macroenvironment of the beta-globin gene appeared similar among the mice strains belonging to one genetic class. Female mice of the C3H strain exogenously transmit mouse mammary tumor virus via the milk, and their offspring have a high incidence of mammary tumor occurrence. DNA isolated from individual mammary tumors taken from C3H mice or from BALB/c mice foster nursed on C3H mothers was analyzed by the DNA filter transfer technique. Additional mouse mammary tumor virus-containing fragments were found in the DNA isolated from each mammary tumor. These proviral sequences were integrated into different genomic sites in each tumor.

Androgenic regulation of messenger RNA sequence complexity in accessory sexual tissues of the male rat studied with fractionated complementary DNA

Effects of androgens on mRNA sequence complexity in the rat seminal vesicle have been investigated using complementary DNA fractionated on the basis of sequence abundance. Total cDNA complementary to poly(A)-rich RNA from normal rats was hybridised with an excess of the same RNA to controlled rot values and then the free cDNA was separated from cDNA . RNA hybrids by hydroxyapatite chromatography. Three cDNA fractions were obtained with very different hybridisation characteristics. Abundant cDNA hybridised to an excess of its parental RNA with an rot 1/2 of 2.46 x 10(-3) mol 1(-1) s and is complementary to about six or seven average-sized sequences. Use of hybrid-arrested translation in a cell-free protein-synthesising system has shown that this class of mRNA includes mRNAs coding for major androgen-dependent secretory proteins. Moderate and scarce cDNA fractions each showed more complex hybridization kinetics; computer analysis suggested each is complementary to two groups of average-sized sequences. Each cDNA fraction was hybridised to excess poly(A)-rich RNA from normal or castrated rats and the kinetics compared. Castration had no effect on the total number of sequences present in any class and did not alter the relative concentration of the scarce sequences. A small (threefold) decrease was seen in the concentration of abundant sequences with a larger (tenfold) decrease in the moderate class. Both de-reases were reversed by testosterone in vivo. The results are consistent with earlier studies where the effects of testosterone on seminal vesicle mRNA were followed using a translation assay and confirm that no gross differential effects are exerted on abundant mRNA coding for major secretory proteins. The cDNA fractions were also used to investigate the overlap in genetic expression between seminal vesicle and ventral prostate. Both tissues share all the scarce sequences in the same relative abundance. Less than 0.0015% and 0.004% of prostatic mRNA is complementary to seminal vesicle abundant and moderate sequences respectively. Similarly prostatic abundant sequences account for less than 0.004% of seminal vesicle mRNA.

Molecular structure and flanking nucleotide sequences of the natural chicken ovomucoid gene

Five independent clones containing the natural chicken ovomucoid gene have been isolated from a chicken gene library. One of these clones, CL21, contains the complete ovomucoid gene and includes more than 3 kb of DNA sequences flanking both termini of the gene. Restriction endonuclease mapping, electron microscopy and direct DNA sequencing analyses of this clone have revealed that the ovomucoid gene is 5.6 kb long and codes for a messenger RNA of 821 nucleotides. The structural gene sequence coding Ifor the mature messenger RNA is split into at least eight segments by a minimum of seven intervening sequences of various sizes. The shortest structural gene segment is only 20 nucleotides long. All seven intervening sequences are located within the peptide coding region of the gene, and the sequences at the 5' and 3' untranslated regions of the mRNA are not interrupted by intervening sequences. The DNA sequences of the regions flanking the 5' and 3' termini of the gene have been determined. Thirty nucleotides before the start of the messenger RNA coding sequence is the heptanucleotide TATATAT, which is also present in a similar location relative to the chicken ovalbumin gene and other unique sequence eucaryotic genes. This sequence resembles that of the Pribnow box in procaryotic genes where a promoter function has been implicated. Seven nucleotides past the 3' end of the gene is the tetranucleotide TTGT, a sequence found to be present at identical locations as either TTTT or TTGT in other eucaryotic genes that have been sequenced. These conserved DNA sequences flanking eucaryotic genes may serve some regulator function in the expression of these genes.

Sequence complexity of bovine pituitary poly(A)RNA

Poly(A)RNA extracted from the anterior lobe of bovine-pituitary tissue was transcribed into its complementary DNA with reverse transcriptase. This 3H-labeled cDNA was hybridized with its template RNA. Hybridization kinetics revealed at least 3 abundance classes with the highest abundance class consisting of only a few different sequences. Bovine-liver poly(A)RNA did not contain this highest abundance class when hybridized to the cDNA probe complementary to pituitary poly(A)RNA. This result suggested that the highest abundance class found in bovine-pituitary poly(A)RNA was specific for that tissue and most likely contained the mRNA sequences for the major pituitary hormones.

Qualitative and quantitative changes in uterine mRNA populations in response to oestradiol treatment of rats

The mRNA population of immature rat uteri, responding to different lengths of oestradiol-induced differentiation, have been compared by the technique of DNA hybridization with heterogeneous RNA. Over the first 4 h of hormone induction there are continuing qualitative and quantitative changes in the poly(A)-containing mRNA such that, by 4 h after oestradiol administration, the population bears little resemblance to that of the unstimulated animal. Between 2 h and 4 h after oestradiol administration, the most striking changes appear to be in sequences of intermediate abundance. The possible significance of these findings is discussed.

Synthesis and characterization of a DNA complementary to pre-uteroglobin mRNA

Uteroglobin, a progesterone-induced uterine protein of the rabbit, is synthesized in cell-free systems as a precursor containing 21 additional amino-acids at its N-terminal end. The mRNA for pre-uteroglobin has been purified from the membrane-bound polysomes of induced endometrium and used as template for the synthesis of a full copy complementary DNA. Final purification of the cDNA was based on hybridization to the template mRNA up to a low value of r0t (0.01 M . s) and digestion of the non-hybridized cDNA by S1 nuclease. A comparison of the hybridization kinetics of the pre-uteroglobin cDNA and rabbit globin cDNA to their respective templates indicates a nucleotide sequence complexity of 650 for pre-uteroglobin mRNA, in agreement with the values obtained by sucrose gradient centrifugation and polyacrylamide gel electrophoresis in formamaide. The melting temperature of the hybrids of pre-uteroglobin cDNA to its template reflects the absence of mismatched sequences. This cDNA has been used to quantify pre-uteroglobin mRNA sequences in the endometrial RNA from control animals and from animals treated sequentially with estradiol and progesterone. In agreement with the induction of uteroglobin-synthesizing activity, there is a dramatic increase in the uterine content of pre-uteroglobin mRNA after hormonal treatment. Part of this effect can be accounted for by hormonally induced cell proliferation. When expressed on a DNA basis there is a 50--100-fold increase in the cellular content of pre-uteroglobin mRNA following hormonal treatment.

Sequence complexities of the poly(A)-containing mRNA in uninfected soybean root and the nodule tissue developed due to the infection by Rhizobium

In order to determine the number of structural genes expressed specifically in root nodules, the total complexities of poly(A) + polysomal RNA populations from uninfected roots and mature nodules were compared. Hybridization kinetics of nodule poly(A) + RNA (NRNA) to its cDNA (NcDNA) revealed a very abundant component comprising 18--20% of the NRNA. This component was shown to be leghaemoglobin (Lb) by the similarity of its kinetics of hybridization to that of purified Lb-cDNA. The hybridization kinetics of uninfected root cDNA (RcDNA) to root poly(A) + RNA (RRNA) indicate that this abundant RNA fraction is absent in RRNA. The extent of sequence homologies between root and nodule tissue was determined by heterologous hybridizations of RcDNA to NRNA and vice versa. The data suggest that the mRNA populations of the two tissues are substantially homologous, though shifts in abundance of certain sequences are quite marked. The hybridization of purified Lb-cDNA to total polysomal RNA from developing nodules shows that the increase in concentration of Lb-mRNA sequences parallels the leghaemoglobin synthesis in this tissue. Lb sequences appear to increase between 8 and 13 days after infection with Rhizobium.

The ovalbumin gene region: common features in the organisation of three genes expressed in chicken oviduct under hormonal control

Two large DNA fragments overlapping the chicken ovalbumin gene have been isolated by molecular cloning. Analysis of these fragments provided a map of a 46,000-base pair region of the chicken genome. This region contains the complete ovalbumin gene (including its mRNA leader-coding sequence) and at least two other genes of unknown function. All three genes are orientated in the same direction and their expression in chicken oviduct is under hormonal control. The three genes share some sequence homologies, suggesting that duplications have occurred in the ovalbumin gene region in the course of evolution.

Distribution of RNA transcripts from structural and intervening sequences of the ovalbumin gene

A study was made of the function of the intervening sequences in the ovalbumin gene, Radioactively labeled DNA probes for the intervening sequences were prepared and RNA's were isolated from whole cells, nuclei, and polysomes of estrogen-stimulated chick oviducts. The concentrations of messenger RNA (mRNA) transcripts from ovalbumin structural sequences (mRNAov) and transcripts corresponding to intervening sequences were then estimated by hybridization to cloned DNA probes. Oviduct tissue contains approximately 58,000 molecules of mRNAov sequences per tubular gland cell and most of these sequences are present in the cytoplasm. In contrast, there are 200 to 300 molecules of RNA per cell which are transcribed from the intervening sequences of the natural ovalbumin gene and almost all of these are found in the nucleus. The difference in distribution of structural and intervening sequence transcripts suggests that, unlike mature mRNA, the intervening sequences are not preferentially transported to cytoplasmic polysomes.

Analysis of the genetic complexity and abundance classes of messenger RNA in human liver and leukemic cells

In an effort to determine the number of genes expressed as messenger RNA in disparate human tissues we have analyzed the genetic complexity of the polyribosome-associated poly(A)-containing RNA population obtained from liver and lymphoblastic leukemic cells. This was accomplished by measuring the kinetics of hybridization of mRNA to a complementary DNA probe synthesized by avian myeloblastosis virus reverse transcriptase in vitro. The results obtained from such an analysis revealed the presence of two major abundance classes of mRNA with a total genetic complexity of approximately 10,000 diverse mRNA species in both of these cell types. Diversity of mRNA species in these unrelated human cells was studied by heterologous hybridization reactions between the cDNA of one cell type and a vast excess of poly(A)-containing mRNA from another. These types of studies indicated that extensive homology (more than 80%) exists in the mRNA sequences of disparate human cell types and suggest that the vast majority of genetic information expressed as mRNA is required for the maintenance of cellular functions common to functionally different human tissues.

Identification of potential ovomucoid mRNA precursors in chick oviduct nuclei

Denaturing gel electrophoresis of chick oviduct nuclear RNA reveals multiple species of RNA that are 1.5-5 times larger than ovomucoid mRNA. By analogy with ovalbumin RNA processing, these data suggest that ovomucoid mRNA is derived from a primary transcript that contains intervening sequences.

The chick ovomucoid gene contains at least six intervening sequences

A 15-kilobase pair EcoRI chick DNA fragment, containing both the termination codon UGA and the 5'-portion of the structural ovomucoid gene, has been cloned in lambda phage Charon 4A by in vitro packaging. Restriction mapping and electron microscopic analyses of this cloned DNA have revealed that the structural ovomucoid gene sequences are separated by at least six intervening sequences.