Purification and properties of ovalbumin messenger RNA

Construction and characterization of type II collagen complementary deoxyribonucleic acid clones

The mRNA for type II collagen was purified from embryonic chick sternum or from purified sternal chondrocytes with guanidine thiocyanate as the extractant. Double-stranded cDNAs to procollagen mRNAs from sternum were synthesized and dC-tailed. After annealing with PstI-cleaved, dG-tailed pBR322, this DNA was used to transform Escherichia coli X1776. Transformed colonies were screened by colony hybridization to type I and II collagen cDNAs. Clones that preferentially hybridized to type II cDNA were characterized further. Four such cDNA clones, pCgII-2, 3, 10 and 12, with inserts of 400, 320, 260 and 750 bp, have been identified as type II collagen cDNA clones by several criteria, including their preference for hybridizing with type II rather than type I collagen mRNAs in hybrid-selected translation experiments.

An improved purification and further characterization of the messenger ribonucleic acid for the fatty acid synthetase from rat liver

High purity fatty acid synthetase mRNA has been prepared from rat liver. The translational purity of the mRNA preparation was at least 27% as judged by the percentage of the radioactivity incorporated into acid-insoluble material that was precipitated by anti-fatty acid synthetase antibody. The specific activity of the mRNA was 220-times greater than that reported previously from this laboratory [1]. The large increase in the specific activity was achieved by the repeated use of high resolution linear-log sucrose density gradient centrifugation and the removal of 28 S rRNA by Sepharose 4B chromatography, as well as by the optimization of the K+ concentration (160 mM) in the reticulocyte lysate translation system. The mRNA preparation showed a single major band on agarose gel electrophoresis under denaturing conditions, and the translational activity of the fatty acid synthetase mRNA on the gel was found to coincide with this band. The molecular weight of the fatty acid synthetase mRNA is 2.5.10(6) Da. The mRNA directed the synthesis of fatty acid synthetase with a molecular weight indistinguishable from that of the authentic enzyme subunit (Mr = 240 000). The copurification of the translation product and authentic enzyme revealed that the fatty acid synthetase polypeptides synthesized in the reticulocyte lysate system are assembled in vitro into dimers, the native form of the enzyme.

Distribution, quantification and biological activity of messenger RNA coding for human chorionic somatomammotropin during normal pregnancy

Synthesis of hCS by RNA fractions from human placentas obtained at different stages of pregnancy was estimated either by immunological or electrophoretical methods in wheat-germ and reticulocyte cell-free systems. hCS synthesis is preferentially associated with polyribosomes bound to the membrane of the endoplasmic reticulum, as is assumed for a secreted protein. In both translational systems we determined only one precursor form of this hormone of a molecular weight near 24 000. Full-term placentas synthesize hCS as the major protein. This conveniently allowed us to isolate the messenger RNA coding for the hormone and to synthesize a specific hCS complementary DNA which we used as a probe for quantifying sequences of RNA coding for hCS during pregnancy. In placentas from first-trimester pregnancy, the concentration of hCS mRNA was 4 times less than in the full-term organs, and the hCS synthesis per microgram of RNA added into the translational medium was diminished in the same order of magnitude. In placentas from second-trimester pregnancy, the concentration of hCS mRNA was similar to that obtained at term, and in vitro the hCS synthesis per microgram of translated RNA was also similar to that observed at the end of pregnancy. However, the hCS mRNA content per placenta from mid-term pregnancy was much lower than from full-term gestation. We established a good parallelism, as pregnancy progressed, between the hCS mRNA content, its capacity of hCS synthesis in vitro and the maternal plasma hCS level, indicating that hCS production is controlled essentially by the biological active mass of the placenta.

Isolation and characterization of xenopus laevis albumin mRNA

The messenger RNA for albumin was isolated from the liver of male frogs. Purification was achieved using oligo(dT)-cellulose chromatography and sucrose gradient centrifugation under denaturing conditions. As judged by translational activity in a cell-free protein-synthesizing system derived from rabbit reticulocytes, albumin mRNA was enriched 259-fold as compared to the total ribonucleic acid of the liver cells. Purified albumin mRNA migrated after sucrose gradient centrifugation as a single symmetrical peak of approximately 17 S and also moved as a single band following denaturing agarose gel electrophoresis. Albumin mRNA possess properties compatible with the presence of a poly(adenylic acid) sequence. Translation in vitro yielded a product which is immunoprecipitable with anti-(frog albumin) and which showed a single radioactive peak having a molecular weight of about 74000 in sodium dodecylsulfate/polyacrylamide gel electrophoresis. Complementary DNA was synthesized using reverse transcriptase, and, as a template, purified albumin mRNA. Following hybridization under conditions of excess RNA, the rot1/2 of albumin mRNA was found to be 1.8 X 10-3 mol . s . 1-1. This result also confirmed that albumin nRNA had been isolated in a highly purified form.

The complete amino-acid sequence of hen ovalbumin

The complete amino acid sequence of hen ovalbumin, comprising 385 residues, has been determined. The sequence was deduced from the 17 cyanogen bromide fragments and from peptides derived by digestion with a number of proteolytic enzymes. The molecular weight of the polypeptide chain of ovalbumin is 42699. Ovalbumin has four sites of postsynthetic modification; in addition to the acetylated N terminus, the carbohydrate moiety is located at Asn-292, and the two phosphorylated serines are at residues 68 and 344. The 'signal sequence' of ovalbumin is between residues 234 and 252. The heptapeptide released during the conversion of ovalbumin to plakalbumin by subtilisin digestion corresponds to residues 346-352. The hen ovalbumin polymorphism characterised by an Asn leads to Asp replacement results from a mutation at residue 311. The amino acid sequence of ovalbumin deduced from these amino acid sequence studies is in complete agreement with the sequence of mRNA determined by McReynolds et al. [Nature (Lond.) 273, 723-728 (1978)].

A DNA segment isolated from chromosomal site 67B in D. melanogaster contains four closely linked heat-shock genes

cDNA clones coding for two different small heat-shock polypeptides were isolated. Both clones hybridize exclusively to the heat-shock puff site 67B, and restriction mapping of embryonic Drosophila melanogaster DNA showed that the two genes probably occur as single copies and are closely linked. The analysis was extended by isolating genomic clones, which contain these genes and two additional ones. The four different genes code for heat-induced poly(A)+ RNAs. These genes are clustered within an 11 kb segment and are separated by spacers of 1.0-4.7 kb. Three of the genes were found to exhibit alternating polarities. Thus in spite of their close linkage, the four heat-induced genes are most likely organized in individual transcription units.

Developmental regulation in cotton seed germination: polyadenylation of stored messenger RNA

Evidence that RNA preexisting in the cotyledons of mature cotton seed (stored mRNA) is polyadenylated during the first day of germination is presented, based on three different experimental data sets. First, actinomycin D is found to inhibit 32PO4 incorporation into mRNA-poly(A) by 62%, into mRNA by 70%, but into poly(A) only 30%. Second, far more 32PO4 and [2-3H]adenosine are incorporated into the poly(A) portion of mRNA-poly(A) than into the mRNA portion as would be expected from their relative sizes and base composition. This underlabeling of the mRNA moiety is enhanced when cotyledons are germinated in actinomycin D. However, an expected distribution of the isotopes between the mRNA and poly(A) moieties is found in cotyledons labeled later in germination. Third, spectral measurements of the absolute amount of mRNA-poly(A) accumulated during the first day of germination in cotyledons germinated in actinomycin D are larger than would be expected from the 70% inhibition of mRNA labeling caused by the drug. The three sets of data suggest that over 50% of the total mass of mRNA polyadenylated during early germination exists in the mature seed. Its complexity, however, has not been measured. These data may explain the sensitivity of much of germination enzyme synthesis to inhibition by 3'dAdo during early germination and its insensitivity to actinomycin D during this period.

The synthesis of presumptive procollagen messenger ribonucleic acid in the calvaria of the developing chick embryo

The presumptive messenger RNAs for type I procollagen were isolated from chick embryo calvaria at various stages of development. Poly(A)-containing RNA fractions from denaturing sucrose gradients directed protein synthesis in a cell-free system derived from wheat germ. Procollagen mRNA activity was detected in a region of about 26 S. Approx. 80% of the labeled proline incorporated into cell-free product was susceptible to digestion by purified bacterial collagenase. The synthesis of procollagen mRNAs was followed during development. Comparison of the in vitro labeled mRNAs from calvaria of day 12--16 embryos indicated that the 26 S component was most pronounced at day 13 and decreased progressively towards day 16. In addition, incubation of calvaria with tritiated nucleosides for 1.5--25 h revealed that 26 S mRNA was significantly labeled only after prolonged periods. The results suggest that procollagen mRNA is a relatively stable species with a prolonged half-life compared to the majority of mRNAs in this tissue.

Reverse transcription of thyroglobulin 33-S mRNA

Bovine thyroglobulin 33-S mRNA has been used as a template for the synthesis of a complementary DNA, using RNA-directed DNA polymerase from the avian myeloblastosis virus. The yield of the reaction was relatively poor and the size of the cDNA did not exceed 10 S. Nevertheless, a copy of high specific radioactivity (approximately 10(7) counts. min-1 microgram-1) could be obtained which hybridized specifically back to its template with an rot1/2 value about 5 times higher than that observed in hybridizations between hemoglobin mRNA (alpha + beta chain) and hemoglobin cDNA. This suggests that thyroglobulin mRNA does not contain extensive internal repetitive sequences. Quantification of thyroglobulin mRNA sequences among various RNA preparations from the beef thyroid was performed using cDNA/RNA hybridizations in RNA excess. The results confirmed that thyroglobulin mRNA represents the large majority of mRNA in membrane-bound polysomes and indicated the virtual absence of thyroglobulin sequences on free polyosomes. The cDNA transcribed from mRNA of bovine origin hybridized efficiently with thyroid RNA from goats, dogs and humans. Although the heterologuous hybrids exhibited the expected decrease in thermal stability, the bovine cDNA provides an appropriate probe for studies dealing with the expression of the thyroglobulin gene in various mammals including man.

Translation of mRNA for glutamate dehydrogenase and spectrophotometric procedure to follow the enzyme biosynthesis

Heterogeneous poly (A)-mRNA fraction was isolated from rat liver microsomes using phenol-chloroform extraction, millipore filtration and poly (U)-agarose affinity chromatography. Obtained fractions were characterized with respect to their secondary structure and poly (A) content. Isolated poly (A)-mRNA fraction contained high template activity for glutamate dehydrogenase in cell-free systems with microsomes or polysomes. A spectrophotometric procedure to follow enzyme biosynthesis was also developed.

Purification and properties of soybean leghemoglobin messenger RNA

Poly(A)-containing leghemoglobin mRNA from soybean root nodules has been purified 84-fold, as judged by its ability to direct the in vitro synthesis of leghemoglobin in a wheat germ system. It has a poly(A) content of 8.6% and a molecular weight, estimated by formamide gel electrophoresis, of 260 000. mRNA with a molecular weight of around 143 000 would be sufficient to code for leghemoglobin. Thus, with respect to both its poly(A) content and its unexpectedly high molecular weight, leghemoglobin mRNA is similar to mRNAs isolated from animal tissues.

Quantitation and characterisation of poly(A)-containing messenger RNAs from mouse neuroblastoma cells

Comparison of several isolation procedures for neuroblastoma poly(A)-containing mRNAs shows that the highest percentage recovery of undegraded and biologically active messenger RNAs is obtained using proteinase K prior to phenol extraction. The messenger RNAs thus isolated comprise approximately 1.5% of the total ribosomal RNAs and have negligible contamination with 18 and 28 S RNAs. On denaturing polyacrylamide gels they have an average molecular weight of 6.5-10(5) with a range from 2.2-10(5) to 1.53-10(6). The messenger RNAs have an average poly(A) content of 154 nucleotides. They are highly active in wheat germ in vitro protein synthesizing systems, giving as much as 4.3 pmol [35S]methionine incorporation into total protein per mol of mRNA. This is almost as active as a control globin mRNA preparation.

The synthesis of polyadenylated RNA and other RNA species in synchronised CHK cells

Chinese hamster kidney cells have been synchronised by the double thymidine block technique. The rate of incorporation of [5-3H]uridine into the polyadenylated RNA fraction has been analysed throughout two complete cell cycles and compared with the rate of incorporation into other RNA species and the UTP pool. In contrast with other reports, we have found that synthesis of 18 S rRNA continues steadily throughout the cell cycle, as does synthesis of 5 S RNA and tRNA. In the case of the polyadenylated RNA, however, our data indicate a major peak of synthesis during S phase and a smaller peak coinciding with G1.

Isolation of specific messenger RNA by adsorption of polysomes to matrix-bound antibody

A procedure is presented for the purification of specific mRNAs, which exploits the ability of antibodies prepared against a native protein to bind to the nascent polypeptide on the polysome. Rather than precipitating these soluble antibody-polysome complexes with anti-antibody, which can lead to nonspecific trapping of polysomes, we have linked the anti-antibody to an insoluble matrix. Thus, the antibody-polysome complex binds to the anti-antibody support and nonspecific polysomes can easily be removed by several washes. We have found para-aminobenzyl cellulose (PAB cellulose), to be a suitable matrix for this purpose. This support can bind large quantities of anti-antibody and it displayed no detectable nonspecific affinity for polysomes or RNA. Using this procedure, we have obtained an apparently homogeneous preparation of ovalbumin mRNA.

Production and properties of vitamin-D-induced mRNA for chick calcium-binding protein

1. Calcium-binding protein synthesis on chick intestinal polysomes is induced within 2 h of injecting vitamin-D-deficient birds with 1,25-dihydroxycholecalciferol. The induction is short-lived: the maximum output of the binding protein is reached by 13 h after hormone injection, and declines rapidly thereafter. 2. This induction of calcium-binding protein synthesis occurs by the production of active mRNA for the protein. The sedimentation coefficient of this mRNA in denaturing conditions is 18 S, equivalent to a molecular weight of approximately 700000, and the molecule contains a tract of polyadenylate. 3. Both polysomal and poly(A)-containing RNA extracted from intestinal polysomes stimulate the synthesis of a range of proteins (up to 70000 molecular weight) by the wheat germ cell-free system. Immunoprecipitable calcium-binding protein is translated from RNA obtained from 1,25-dihydroxycholecalciferol-dosed birds but not from control birds. This calcium-binding protein is the same size (27000 molecular weight) as authentic chick calcium-binding protein; No other proteins are specifically precipitated by the antiserum. Thus in chickens 1,25-dihydroxycholecalciferol-induced calcium-binding protein is not synthesised via any precursor molecule. The implications of this result are discussed.

Isolation and characterization of purified rat casein messenger ribonucleic acids

Purification of casein messenger ribonucleic acids (mRNAs) from lactating rat mammary gland RNA has been accomplished by a combination of sizing techniques, including Sepharose 4B chromatography and preparative agarose-urea gel electrophoresis, and affinity chromatography of poly(adenylic acid)-containing mRNA on oligo(dT)-cellulose. The separation of the individual casein mRNAs into discrete molecular species free of apparent ribosomal RNA contaminants was facilitated by the use of denaturing conditions either prior to or during each of the fractionation procedures. Two casein mRNA fractions were isolated: (1) a 15S mRNA doublet which directed the synthesis of the two largest rat caseins in the wheat-germ, cell-free, translation assay, and (2) a 12S mRNA which migrated as a single species during agarose-urea gel electrophoresis and directed the in vitro synthesis of the smallest of three rat caseins. These mRNAs had apparent molecular weights of 450 000 +/- 30 000 and 320 000 +/- 25 000 and contained poly(adenylic acid) sequences at their 3' termini ranging from 15 to 150 residues with number average lengths of 42 and 38 adenosines, respectively. The purity of the isolated casein mRNA'S was determined both by agarose-urea gel electrophoresis and by a careful comparison of the total products synthesized in the wheat-germ translation assay with those recognized by a specific casein antibody using an indirect immunoprecipitation technique. The specificity of the indirect immunoassay procedure was demonstrated by the selective displacement by purified rat casein of greater than 95% of the radioactive product synthesized in the cell-free system. Under optimal translation conditions for casein mRNA, at least 90% of the released protein synthesized in response to the 15S casein mRNA was specifically immunoprecipitable, representing a 178-fold purification compared with the initial RNA extract. Using these techniques a comparable purification was also obtained for a 15S mouse casein mRNA fraction. Finally, an analysis by fluorography on 5-20% (w/v) polyacrylamide gradient slab gels of the total proteins synthesized in response to both the 15S and 12S casein mRNAs revealed a close correspondence with those proteins which were specifically immunoprecipitated.

Guinea-pig milk-protein synthesis. Isolation and characterization of messenger ribonucleic acids from lactating mammary gland and identification of caseins and pre-alpha-lactalbumin as translation products in heterologous cell-free systems

1. The major milk proteins synthesized by the lactating mammary gland of the guinea pig were identified and designated as caseins A, B and C and alpha-lactalbumin, with estimated mol.wts. of 28000, 25500, 20500 and 14500 respectively. 2. Antisera to the total casein fraction and to alpha-lactalbumin were prepared from rabbits. The milk proteins were also iodinated with either 131I or 125I. 3. A poly(A)-rich RNA fraction was isolated from lactating guinea-pig mammary glands. Isolation was by affinity chromatography on oligo(dT)-cellulose. 4. Examination of this RNA fraction by electrophoresis on polyacrylamide gels containing formamide indicated three major species 1, 2 and 3, with estimated wol.wts. of 5.4 X 10(5) and 3.3 X 10(5), and the apparent absence of rRNA species. 5. The poly(A)-rich RNA stimulated protein synthesis in heterologous cell-free systems based on wheat germ, Krebs II ascites-tumour cells, and the latter supplemented with an initiation factor-3 fraction from rabbit reticulocyte ribosomes. 6. Between 80 and 90% of the protein synthesis directed by the mRNA was for milk proteins. 7. Analysis of the proteins immunoprecipitated by the alpha-lactalbumin antiserum showed in the wheat-germ system that the product was a protein with a molecular weight greater than that of alpha-lactalbumin, whereas in the ascites-tumour-cell systems both this protein and alpha-lactalbumin were found. When the larger protein was treated with CNBr and the resulting peptides were examined, it was shown that the extra peptide was at the N-terminus. This and other evidence is adduced for the initial translation product of alpha-lactalbumin being a precursor with an addition of about ten amino acids at the N-terminus. 8. Similar analysis of the casein immlnospecific proteins produced under the direction of mRNA indicated that the products had a molecular weight that was apparently a littel smaller than that of the caseins synthesized in vivo. This was not consistent with higher-molecular weight casein precursors. 9. Possible explanations for the results obtained are discussed, especially in terms of the physiological significance of the pre-alpha-lactalbumin as a secretory protein.

The transcripts of Balbiani rings from Chironomus thummi. Giant RNA molecules with messenger characteristics

Experimental results on the transcription of Balbiani rings BR 1 and BR 2 of Chironomus thummi salivary gland chromosomes are presented. The DNA of Balbiani ring 2, which is the most active puff in larvae, is transcribed into large RNA molecules of about 22 X 10(6) D which resist degradation by heating, formamide or urea treatment. The asymmetrical distribution of electrophoretic profiles of BR 2 RNA and the appearence of a symmetrical BR RNA peak in the nucleoplasm suggest the synthesis of (mainly) one RNA fraction in BR 2. The gel electrophoretic patterns of BR 1 RNA are, on the other hand, characterized by the appearance of two main fractions of high molecular weight RNA, one of which corresponds in molecular weight (about 22 X 10(6) D) to BR 2 RNA. The second RNA fraction is significantly smaller in molecular size (molecular weight: about 10 X 10(6) D) and, like the 22 X 10(6) D RNA fractions of the two Balbiani rings, resistant against heating in 8 M urea. Binding to poly (U) sepharose of a significant part of Balbiani ring RNA suggests the existence of poly (A) and/or oligo (A) sequences in the Balbiani ring RNA. -- In situ hybridization of BR RNA to the salivary gland chromosomes reveals accumulation of silver grains over the Balbiani ring regions only and demonstrates the restriction of BR DNA sequences to the corresponding Balbiani ring.

Effect of 5-bromodeoxyuridine on the appearance of cytoplasmic poly-A containing RNA

Cytoplasmic poly-A containing RNA, synthesized by cultured chick embryo cells, was examined during growth in 5-bromodeoxyuridine. The kinetics of 3H-adenosine incorporation into this species of RNA, when compared to the rest of the cytoplasmic RNA, and to control cells, indicates that the rate of synthesis of this RNA is slower in BrdU treated cells. An examination of the rate at which a steady state distribution of radioactivity, between the poly-A segment and non-poly-A portion of poly-A containing RNA is reached also indicated that this species is synthesized at a lower rate in BrdU treated cells.

A significant lag in the induction of ovalbumin messenger RNA by steroid hormones: a receptor translocation hypothesis

Although ovalbumin and conalbumin mRNA accumulate in the same tubular gland cells of the chick oviduct in response to estrogen or progesterone treatment, the kinetics of induction are markedly different. Conalbumin mRNA begins to accumulate within 30 min after estrogen administration, whereas there is a lag of approximately 3 hr before ovalbumin mRNA begins to accumulate, as measured by three independent assays. The kinetics of estrogen-receptor binding to chromatin indicate that these sites are saturated within 15 min of estrogen administration to the chicks, demonstrating that the lag is not due to slow uptake of the steroid. Suboptimal doses of estrogen produce the same lag, but the resultant rate of ovalbumin mRNA accumulation is lower than with an optimal dose. Partial induction of ovalbumin mRNA by a low dose of estrogen does not shorten the lag with an optimal dose. With progesteone, there is a lag of about 2 hr before either ovalbumin or conalbumin mRNA begins to accumulate. Treatment of chicks with hydroxyurea shortens the lag for ovalbumin induction with either hormone. Inhibition of protein synthesis with emetine does not prevent the accumulation of either ovalbumin or conalbumin mRNA. With cycloheximide, however, ovalbumin mRNA accumulation can be prevented. The existence of a lag suggests that there are intermediate steps between the binding of steroid receptors to chromatin and the induction of ovalbumin mRNA. There are basically two models to explain these delays in response: one involving the accumulation of an essential intermediate, and the other involving a rate-limiting translocation of steroid receptors from initial nonproductive chromatin-binding sites to productive sites. Several aspects of the kinetics of ovalbumin mRNA induction are more consistent with the latter model.

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

The effects of estrogen, progesterone and estrogen + progesterone combined on nuclear transcriptional processes in oviducts of immature chicks, previously withdrawn from estrogen, are reported. The responses to the steroids of the endogenous nuclear RNA polymerase activities, both nucleolar (I) and nucleoplasmic (II), the chromatin compositions and template capacities, and the appearance of ovalbumin messenger RNA (mRNA) are compared. When immature chicks (previously treated at 14 days with estrogen) are withdrawn from estrogen treatment, there is a gradual reduction in both polymerase activities. Diurnal variations in polymerase II activties in the oviduct of withdrawn chicks required that subsequent experiments include time-matched controls. The hormones alter RNA polymerase II and II activities in vivo as assayed in isolated nuclei. Progesterone represses the polymerase I and II activities, while estrogen alone and estrogen + progesterone enhance both polymerase activities immediately after injection. Diethylstillbestrol, a synthetic estrogen, causes changes similar to those of estrogen. The effects of these steroids on the polymerases are detected within 15 min of hormone injection. Changes in the capacities of chromatins to serve as template for RNA synthesis in general correlated with changes in polymerase II activities. Interestingly, in the case of estrogen treatment, the acidic chromatin protein (but not histone) levels fluctuate positively with the template capacities of the chromatin. An antagonism between estrogen and progesterone is observed in the responses of both RNA polymerases I and II activities as well as in the chromatin template capacity. Levels of messenger RNA coding for ovalbumin, as detected by hybridization with labeled complementary DNA, increase in oviducts of withdrawn chicks within 2--3 of the injection of estrogen, progesterone or estrogen + progesterone. This rapid accumulation of ovalbumin mRNA is not accompanied in each case by a similar increase in polymerase II activity or chromatin template capacity.

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.

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.

Characterization of adenovirus type 2 transcriptional complexes isolated from infected HeLa cell nuclei

HeLa cell nuclei, isolated 17 h after infection with human adenovirus type 2 (Ad2), were treated with 200 mM ammonium sulfate. The extract (S200 fraction) contained 50 to 70% of the nonintegrated Ad2 DNA, which was in the form of nucleoprotein complexes. These complexes contained native, intact Ad2 DNA (with the exception of replicative intermediates) and could be partially purified and resolved by velocity gradient centrifugation. Using high-salt (200 mM ammonium sulfate) incubation conditions, more than 95% of the nuclear RNA polymerase activity belonged to class B. About 45% of the class B enzyme molecules bound to DNA in the nuclei (those "engaged" in RNA synthesis) were released from the nuclei in the form of Ad2 transcriptional complexes by treatment with 200 mM ammonium sulfate. At least 90% of the RNA synthesized in high salt in the nuclei or in the S200 fraction was Ad2 specific, and essentially all of this RNA was complementary to the l strand of Ad2 DNA. These findings are compatible with what is known about Ad2-specific RNA synthesis in vivo. The analysis of the RNA synthesized from partially purified transcriptional complexes supports the contention that its transcription is almost entirely asymmetric, and that the asymmetry observed in vivo is not a consequence of the rapid degradation of h-strand transcripts. The RNA synthesized in vitro in the absence of detectable RNase activity sedimented with a maximum size of 35 to 40S. Less than 5% of the nuclear or the S200 fraction RNA polymerase activity was class C when assayed under non-reinitiating conditions. Although much of the RNA synthesized by the class C enzyme was Ad2 specific, 5.5S virus-associated RNA was not the predominant product. The isolation of Ad2 DNA transcriptional complexes provides an attractive system for further characterizing the Ad2 DNA template used for transcription and for studying the regulation of the expression of the Ad2 genome during the productive infection cycle.