Decreased ribonucleic acid synthesis in isolated rat liver nuclei during starvation

1. Isolated nuclei from starved rats showed a lowered incorporation of [(14)C]UMP into RNA. 2. The Mg(2+)-dependent incorporation was decreased by 30% after 1 day of starvation, but incorporation in the presence of Mn(2+) and ammonium sulphate decreased only after longer periods of starvation. 3. RNA synthesis by nuclei in the presence of excess of added RNA polymerase was unchanged after 1 day of starvation and was inhibited by 20% after 4 days. 4. The capacity of nuclei to bind actinomycin D was unchanged after 1 day and was decreased by 20% after 4 days of starvation.     

Synthesis of ribonucleic acid by isolated rat liver mitochondria

Rat liver mitochondria isolated in sucrose-N-tris(hydroxymethyl)methyl-2-aminoethane-sulphonic acid (TES) incorporated [(3)H]UTP into RNA for 1h. Incorporation was inhibited 50% by 1mug of actinomycin D/ml, 1mug of acriflavine/ml and 0.5mug of ethidium bromide/ml but was insensitive to rifampicin, rifamycin SV, streptovarcin and deoxyribonuclease. After the first 10min of incubation, the synthesis was insensitive to ribonuclease. RNA synthesis by mitochondria isolated in sucrose-EDTA was insensitive to actinomycin D and sensitive to ribonuclease during the first 10min of the incubation but thereafter the sensitivities were the same as for mitochondria isolated in sucrose-TES. In a hypo-osmotic medium the relative extent of incorporation of the four ribonucleoside triphosphates into RNA was CTP>UTP=ATP>GTP. In an iso-osmotic medium the incorporation of CTP and GTP decreased. All four nucleotides were incorporated into RNA in a DNA-dependent process, as indicated by the inhibition by actinomycin D. In addition, CTP and ATP were incorporated into the CCA end of mitochondrial tRNA. ATP was also incorporated into an unidentified acid-insoluble compound, which hydrolysed in alkali to a product that was not ATP, ADP or 5'- or 2(3')-AMP. Atractyloside inhibited the incorporation of ATP into RNA with 50% inhibition at 2-3nmol/mg of protein. The [(3)H]UTP-labelled RNA had peaks of 16S and 13S characteristic of mitochondrial rRNA. In addition a peak at 20-21S was observed as well as heterogeneous RNA sedimenting throughout the gradient. The synthesis of all these species was inhibited by actinomycin D, indicating that rat liver mitochondrial DNA codes for mitochondrial rRNA as well as other as yet unidentified species.     

Synthesis and maturation of ribosomal ribonucleic acids in isolated HeLa cell nuclei. A tracer study on the topology of the 45S precursor of ribosomal ribonucleic acids

The synthesis and processing of RNA by isolated HeLa cell nuclei was studied at low ionic strength in the presence of alpha-amanitin. The RNA polymerase reaction, with endogenous template and enzyme, rapidly reaches a plateau dependent on the amount of nuclei. Evidence is presented that incorporation of [(3)H]UMP proceeds only in growing RNA chains, whereas initiation of new RNA chains is arrested. The product formed contains all the main components of the 45S pre-rRNA (precursor of rRNA) maturation pathway (45S, 32S and 20S pre-rRNA; 28S and 18S rRNA). Most of the labelled material is in the mature rRNA components and their immediate precursors, even at very short times of incubation (2min). Small, but definite, 5S and 4S RNA peaks are also observed. At shorter incubation times a substantial amount of [(3)H]UMP is incorporated into RNA molecules in the 24S and 10-16S zones. This RNA material is considered to represent the non-conserved segments of 45S pre-rRNA in the process of nucleolytic degradation. A model for the tracer study of the topology of 45S pre-rRNA, on arrest of rRNA initiation, is discussed. The experimental evidence obtained supports the following structure of 45S pre-rRNA: 5'-end-28S rRNA unit-18S rRNA unit-nonconserved segment-3'-end.     

The effect of actinomycin D on the synthesis of ribonucleic acid and protein in rat liver parenchymal cells in suspension and liver slices

1. Rat liver parenchymal cells in suspension are shown to require a higher concentration of actinomycin D than liver slices for equivalent inhibition of the incorporation of [(14)C]adenine, [(14)C]uracil and [(32)P]phosphate into RNA, and of (14)C-labelled amino acids into protein; protein synthesis is much less susceptible to actinomycin D inhibition than RNA synthesis in both the tissue preparations. Possible causes for these differences are discussed. 2. The uptake of [(3)H]actinomycin D in the first few minutes was much greater in the cell suspensions than in the tissue slices; that in the next 1-4hr. was about the same in both the cases. The uptake by both the tissue preparations was at all times proportional to the concentration of the drug within the range 0.5-2.0mug./ml. 3. In the slices actinomycin D taken up initially was concentrated almost exclusively in the nuclei; with time the concentration of the drug in the mitochondria and the supernatant increased more rapidly than in the nuclei though at no stage did it exceed that in the nuclei. In the cell suspension the largest concentration of the drug taken up initially was found in the supernatant; most of the drug taken up subsequently also stayed in the supernatant. 4. When the drug concentration in the incubation medium was 1mug./ml., its concentration within the parenchymal cells in suspension and the parenchymal cells in the slices reached 2.2 and 1.6mug./cm.(3) of cellular volume respectively. On average, 7% of the drug was removed from the medium by the cells in suspension and 23% by the cells in the slices; the average ratio of intracellular to extracellular concentration was 2.4 in the former and 2.1 in the latter case.     

Characterization of the ribonucleic acid synthesized by isolated rat-liver nuclei

1. Isolated rat-liver nuclei incorporated [¹⁴C]UMP into RNA when incubated in the presence of Mg²⁺ and all four ribonucleoside triphosphates. The addition of bentonite to the system diminished the breakdown of the newly synthesized RNA. 2. AMP and CMP were incorporated in the absence of the other added triphosphates, and in the presence of deoxyribonuclease. 3. RNA synthesized in the presence of Mg²⁺ contained a high proportion of CMP and GMP, and sedimented in the regions of ribosomal RNA and of heavier molecules. About 1% of this RNA hybridized with homologous DNA, and hybrid formation was more effectively inhibited by nuclear RNA than by ribosomal RNA. 4. RNA synthesized in the presence of Mn²⁺ plus ammonium sulphate had a composition intermediate between that of ribosomal RNA and of DNA, and about 4% of this RNA formed hybrids with DNA. 5. Less than 2% of the newly synthesized RNA was capable of forming ribonuclease- and deoxyribonuclease-resistant complexes. 6. It was concluded that the newly synthesized RNA arose as a result of an asymmetric process and included both ribosomal and DNA-like species.     

The synthesis of ribonucleic acid in vivo in the nuclei of rat brain fractionated by zonal centrifugation

1. Radioactive orotic acid, uridine and adenosine were administered to rats by intracisternal injection. The effects of the size of the dose, the specific radioactivity and time on the incorporation into the RNA of unfractionated nuclei of brain tissue were examined to establish appropriate conditions for studies of the relative activities in vivo of the various sorts of brain nuclei fractionated by zonal centrifugation. Uridine is incorporated more efficiently than either orotic acid or adenosine. 2. With [(3)H]uridine as precursor the astrocytes in zone (II) contain the highest radioactivity except at the beginning of the experiment when the neuronal nuclei of zone (I) are more highly labelled. This fraction utilizes [(14)C]orotic acid more readily than the nuclei of zone (II). The astrocytic nuclei of zone (III) show a general resemblance to those of zone (II). Considerable differences between the incorporations into the two types of oligodendrocyte nuclei in zones (IV) and (V) are observed. 3. The relative synthetic activities of the major types of brain nuclei in vitro and in vivo are discussed.     

Stimulation by insulin of the formation of ribonucleic acid and protein by mammary tissues in vitro

1. Insulin is one of the hormones that are essential for successful tissue culture of explants of the mammary glands of pregnant mice. We report here effects of insulin on RNA and protein formation by mammary tissue from pregnant mice and rats incubated in tissue-culture medium 199. 2. The incorporation of [(14)C]adenine over 3hr. into the RNA of explants of the mammary glands of pregnant mice was increased by an average of 68% when the medium contained 5mug. of insulin/ml. Under similar conditions the incorporation into the RNA of slices of the glands of pregnant rats was increased by an average of 61%. Incorporation into the RNA of slices from lactating rats was stimulated to a smaller extent. 3. Adipose tissue was separated from the glands of pregnant mice and the effect of insulin on the incorporation of adenine into its RNA was studied. In whole explants the incorporation of adenine, both with and without insulin, is almost entirely into the RNA of the mammary parenchyma and not of the adipose tissue. 4. Insulin also stimulated by 38% the incorporation of [(14)C]leucine over 3hr. into the proteins of slices of the glands of pregnant rats. It had no significant effect on slices from lactating rats. 5. Actinomycin D (10mug./ml.) decreased the incorporation of [(14)C]adenine into the RNA of slices of the glands of pregnant rats by an average of 97%. Though it also decreased the incorporation of [(14)C]leucine into the proteins by an average of 25%, the percentage stimulation by insulin of this incorporation remained unchanged.     

Stimulation of incorporation of nucleic acid precursors into HeLa cells caused by provaline

1. The effect of proflavine and other acridines on the incorporation of precursors into the nucleic acids of HeLa cells was examined. 2. Relatively low concentrations (50mum) of proflavine completely inhibited incorporation of precursors into DNA, but allowed a small extent of incorporation into RNA. 3. Acridine-resistant incorporation into RNA was unaffected by actinomycin D at 2mug./ml. and persisted even at high concentrations (500mum) of many acridines. 4. A few combinations of acridine and precursor, notably 250mum-proflavine and [(14)C]adenine, caused a stimulation of incorporation. 5. The proflavine-stimulated incorporation was into alkali-stable di- and tri-nucleotides. 6. It was concluded that the effect was due to the preferential inhibition of degradation of a fraction of RNA that normally turned over, thus allowing small radioactive oligonucleotides to accumulate in the cells.     

Polyphasic changes in incorporation of precursors into ribonucleic acid of oestradiol-stimulated mammary gland

1. At 3 weeks after ovariectomy, mammary glands (5th pair) of adult Swiss mice show (i) no significant decrease in weight, (ii) 20% of the original rate of incorporation of [(3)H]-uridine into RNA (after a 30min pulse), and (iii) 90% of the original rate of incorporation of l-[(3)H]leucine into protein (after a 15min pulse). 2. A single injection of oestradiol-17beta into these ovariectomized mice produces, during the next 17h, a series of discrete bursts of increased incorporation of [(3)H]uridine into mammary-gland RNA; the bursts, which are variable in height, reach peaks at approx. 1, 9, 12 and 16h after hormone administration; an increase is already detected at 15min, the earliest time-point investigated; each burst lasts for approx. 2h. There is no significant stimulation of [(3)H]uridine incorporation into RNA of liver and quadriceps femoris muscle. 3. Nuclear incorporation of [(3)H]UTP into RNA of mammary gland in vitro is linear with time for up to 20min at 15 degrees C; it requires CTP, GTP and ATP and is inhibited by actinomycin D. Also, the incorporation is strongly inhibited by alpha-amanitin in high salt concentrations but only weakly in low salt concentrations, a result indicating that RNA polymerase II activity predominates in high salt, whereas RNA polymerase I activity predominates in low salt concentrations. Injection of oestradiol-17beta in vivo followed by measurement of nuclear RNA synthesis in vitro shows a definite increase in both RNA polymerase activities 30min after oestradiol-17beta injection, the earliest time-point investigated, a higher increase at 1h, a decline at 4h, and again a large increase at 12h. These results in general agree with the changes in precursor incorporation into RNA measured directly in the animal and suggest that changes in [(3)H]uridine uptake into RNA are not precursor-pool-dependent.     

Effects of pancreozymin, urecholine and actinomycin D on the metabolism of ribonucleic acid by canine pancreas

1. Canine pancreas slices were incubated with [6-(14)C]orotic acid and the rate of its incorporation into RNA was measured. RNA was fractionated by shaking homogenates with phenol at 2 degrees , 50 degrees , 65 degrees and 80 degrees . Cytoplasmic RNA was extracted at the lowest temperature and nuclear RNA at the higher temperatures. The samples were centrifuged through sucrose gradients and the E(260) and (14)C-sedimentation patterns determined. Incorporation of orotic acid was very rapid into cytoplasmic 4s RNA. This probably represents end-group turnover. No incorporation into cytoplasmic ribosomal RNA was observed. 2. The nuclear 50 degrees -RNA exhibited two E(260) peaks, at 18s and 28s. This portion of the sample contained but moderate amounts of [(14)C]RNA. The highly labelled material had sedimentation coefficients in the range 35-50s. The nuclear 65 degrees -RNA showed an E(260) peak at 16s. The [(14)C]RNA peak occurred at 25-35s and this portion demonstrated the highest specific activity of any RNA fraction. 3. The 50 degrees -RNA, 65 degrees -RNA and 80 degrees -RNA were hydrolysed and their base compositions were determined. All three samples possess a ribosomal type of composition (G+C)/(A+U)=(1.4-1.7). For this reason they are considered to contain ribosomal precursor RNA as their major constituent. 4. Actinomycin D (0.5mug./ml.) in the incubation medium inhibited incorporation of orotic acid into both nuclear fractions but not into 4s RNA. 5. The cholinergic drug Urecholine inhibited incorporation into the heavy, high-specific-activity portions of the nuclear fractions but did not inhibit incorporation into the ribosomal precursor type of nuclear RNA. A similar result was also obtained with the hormone pancreozymin. Moderate inhibition of incorporation of orotic acid into 4s RNA likewise resulted from the presence of the drug and the hormone.     

Ribosomal-type ribonucleic acid from rodent mitochondria

1. Highly purified mitochondria containing 3.0mug of RNA/mg of mitochondrial protein were prepared from rat liver by differential centrifugation. 2. RNA, labelled with [(32)P]P(i) or [(3)H]orotate, was isolated from these mitochondria by a phenol extraction method. The RNA sedimented at 15S and 13S on sucrose density gradients. Its nucleotide composition was 23% uridylate, 30% adenylate, 22% guanylate and 25% cytidylate. 3. RNA from mouse L cells was labelled with [(3)H]-uridine in the presence of 0.1mug of actinomycin D/ml to suppress the synthesis of cytoplasmic rRNA. The RNA isolated from crude L-cell mitochondria by a cold-phenol-sodium dodecyl sulphate method had components sedimenting at 15S and 12.5S. These components had an electrophoretic mobility on agarose-acrylamide gels of 21 and 12S(E) compared with 28 and 18S(E) for cytoplasmic rRNA. The nucleotide composition was 26% uridylate, 34% adenylate, 18% guanylate and 22% cytidylate. 4. RNA extracted from crude L-cell mitochondria by a hotphenol-sodium dodecyl sulphate method had an additional component sedimenting at 21S and having an electrophoretic mobility of 18S(E). It was probably DNA because of its sensitivity to deoxyribonuclease and its insensitivity to ribonuclease and alkali. It was present in nuclear fragments contaminating the crude mitochondrial fraction and could be removed by deoxyribonuclease or isopycnic-gradient centrifugation.     

Partial purification of a ribosomal ribonucleic acid methylase from rat liver nuclei and methylation of undermethylated nuclear ribonucleic acid from regenerating liver of ethionine-treated rat

S-Adenosylmethionine-dependent ribosomal RNA (rRNA) methylase has been purified approx. 90-fold from rat liver nuclei. The partially purified methylase catalyzes the methylation of base and ribose in hypomethylated nuclear rRNA prepared from the regenerating rat liver after treatment with ethionine and adenine. The enzyme has an apparent molecular weight of about 3 x 10(4) and a sedimentation coefficient of 3.0 S. The enzyme is optimally active at pH 9.5 and sensitive to p-chloromercuribenzoate. Thiol-protecting reagents, such as dithiothreitol, are necessary for its activity, and the enzyme requires no divalent cations for its full activity. This enzyme did not efficiently transfer the methyl group to nuclear rRNA from normal rat liver, compared with hypomethylated nuclear rRNA. Methyl groups were mainly incorporated into pre-rRNA larger than 28 S, and the extent of 2'-O-methylation of ribose by this enzyme was greater than that of base methylation in the hypomethylated rRNA. No other nucleic acids, including transfer RNA (tRNA) and microsomal RNA from normal as well as ethionine-treated rat livers, tRNA from Escherichia coli, yeast RNA, and DNA from rat liver and calf thymus, were significantly methylated by this methylase. These results suggest that partially purified rRNA methylase from rat liver nuclei incorporates methyl groups into hypomethylated pre-rRNA from S-adenosylmethionine.     

Ribonucleic acid synthesis in vitro in primary spermatocytes isolated from rat testis

The incorporation of [(3)H]uridine into RNA was studied quantitatively (by incorporation of [(3)H]uridine into acid-precipitable material) and qualitatively (by phenol extraction and electrophoretic separation of RNA in polyacrylamide gels) in preparations enriched in primary spermatocytes, obtained from testes of rats 26 or 32 days old. The rate of incorporation of [(3)H]uridine into RNA of isolated spermatocytes was constant during the first 8h of incubation, after which it decreased, but the decreased rate of incorporation was not reflected in a marked change in electrophoretic profiles of labelled RNA. In isolated spermatocytes, [(3)H]uridine was incorporated mainly into heterogeneous RNA with a low electrophoretic mobility. Most of this RNA was labile, as shown when further RNA synthesis was inhibited with actinomycin D. Spermatocytes in vivo also synthesized heterogeneous RNA with a low electrophoretic mobility. A low rate of incorporation of [(3)H]uridine into rRNA of isolated spermatocytes was observed. The cleavage of 32S precursor rRNA to 28S rRNA was probably retarded in spermatocytes in vitro as well as in vivo. RNA synthesis by preparations enriched in early spermatids or Sertoli cells was qualitatatively different from RNA synthesis by the spermatocyte preparations. It is concluded that isolated primary spermatocytes maintain a specific pattern of RNA synthesis, which resembles RNA synthesis in spermatocytes in vivo. Therefore isolated spermatocytes of the rat can be used for studying the possible regulation of RNA synthesis during the meiotic prophase.     

Free pyrimidine nucleotide pool of Ehrlich ascites-tumour cells. Compartmentation with respect to the synthesis of heterogeneous nuclear RNA and precursors to ribosomal RNA.

The incorporation of [14C]orotate and [14C]uridine into UMP residues of hnRNA (heterogeneous nuclear RNA) and pre-rRNA (precursors to rRNA) of Eharlich ascites-tumour cells was compared: orotate was incorporated at a markedly higher rate into hnRNA. On the other hand, the rate of incorporation of uridine into pre-rRTNA was even somewhat higher than into hnRNA. The ratio of specific radioactivities of CMP to UMP residues in pre-rRNA and hnRNA was studied. At all times of labelling this ratio was similar for both RNA species independently of the precursor used. On addition of excess unlabelled uridine, the CMP/UMP labelling ratio in both pre-rRNA and hnRNA rose. However, this increase was much more pronounced with hnRNA. It is concluded that nuclear pyrimidine nucleotide pool for RNA synthesis is compartmentalized. The synthesis of hnRNa is supplied preferentially by the large and the small compartment, respectively. A detailed model for the cellular compartmentation of uridine nucleotide precursors to RNA is proposed.U     

Initiation of RNA synthesis in isolated rat liver nuclei

Isolated rat liver nuclei were incubated under conditions when RNA polymerase I or RNA polymerase II was preferentially active. It was shown that [gamma-32P] ATP and [gamma-32P] GTP were incorporated into phenol extractable, TCA-precipitable material. RNase, actinomycin D, heparin and, in the case of RNA-polymerase II, alpha-amanitine inhibited precursor incorporation. These data are interpreted as evidence in favour of the initiation of RNA synthesis in isolated rat liver nuclei.     

RNA synthesis in isolated nuclei of the dinoflagellate Crypthecodinium cohnii

Atypical eukaryotic RNA polymerase activity was demonstrated in nuclei of Crypthecodinium cohnii, a eukaryote devoid of histones. Nuclei were isolated from growing cultures of this dinoflagellate and assayed for endogenous RNA polymerase (EC 2.7.7.6) activity. There was a biphasic response to Mg2+ with optima at approximately 0.01 and 0.02 M MgCl2, but in contrast to other eukaryotic RNA polymerases, this enzyme activity was inhibited by low MnCl2 concentrations. In the presence of 0.01 M MgCL2 the optimum (NH4)2SO4 concentration was 0.025 M, a concentration at which the nuclei were lysed. Incorporation of [3H]UMP into RNA was inhibited by actinomycin D and dependent on the presence of undergraded DNA, and the reaction product was sensitive to ribonuclease and KOH digestion. Omission of one or more ribonucleoside triphosphates greatly reduced the incorporation. Only a slight enhancement of RNA polymerase activity resulted from the addition of various amounts of native and denatured calf thymus DNA. Spermine caused a marked inhibition while spermidine had little effect on RNA synthesis in the nuclei. Under the optimum conditions described in the present paper the nuclei incorporated approximately 3 pmoles of [3H]UMP/microgram DNA at 25 C for 15 min, and approximately 80% of this activity was inhibited by the eukaryotic RNA polymerase II inhibitor, alpha-amanitin (20 micrograms/ml). A unique situation therefore exists in C. cohnii nuclei, in which absence of histones (a prokaryotic trait) is combined with alpha-amanitin-sensitive RNA polymerase activity (a eukaryotic trait).     

Inhibition by soluble ribonucleic acid of stimulatory effect of liver template ribonucleic acid

1. Liver soluble RNA (s-RNA) and, to a smaller extent, Escherichia coli s-RNA inhibited the stimulation of [(14)C]leucine incorporation into protein in an E. coli S-30 system brought about by liver microsomal RNA or polyuridylic acid as template. 2. The inhibitory activity was associated with the fraction of the s-RNA possessing transfer-RNA activity. 3. The inhibition was exercised at a stage after charging of the s-RNA with amino acid. 4. Neither the method of preparation of the s-RNA nor its state of amino acid acylation affected its inhibitory action. 5. Stimulation of [(14)C]phenylalanine incorporation by polyuridylic acid or by liver microsomal RNA was not inhibited by addition of s-RNA. 6. It appears that excess of s-RNA inhibits the ambiguous incorporation of leucine with polyuridylic acid and also that something similar occurs with a natural template. 7. Estimation of messenger activity of samples of RNA should be carried out only after removal of s-RNA.     

Ribonucleic acid and protein synthesis in Rhizophlyctis rosea zoospores

LéJohn, Herbert B. (Purdue University, Lafayette, Ind.), and James S. Lovett. Ribonucleic acid and protein synthesis in Rhizophlyctis rosea zoospores. J. Bacteriol. 91:709-717. 1966.-The uniflagellate zoospores of Rhizophlyctis rosea display active motility and a high endogenous respiratory metabolism, but neither growth nor net ribonucleic acid (RNA) or protein synthesis can be measured by ordinary procedures. Nevertheless, synthesis can be detected with isotopic precursors. Uracil-C(14) is incorporated slowly into both the soluble and ribosomal RNA. Analysis of zoospore extracts (on diethylaminoethyl cellulose columns or sucrose gradients) after various periods of labeling suggested that most of the uracil incorporation represents slow synthesis of ribosomal precursor RNA and, ultimately, ribosomes. Actinomycin D caused an 80% inhibition of uracil incorporation. The most rapidly labeled RNA was susceptible to extensive degradation in cells treated with actinomycin, but the percentage of stable RNA increased with the time of incorporation before addition of the antibiotic. Neither the effects of actinomycin nor the results of chase experiments have established unequivocally the existence of turnover or the presence of a short-lived "messenger" fraction in motile spores. Both leucine and methionine were slowly incorporated into a spectrum of cellular proteins. The methyl group of C(14)-methylmethionine also served as a methyl donor for the methylation of soluble RNA but not of ribosomal RNA. The observations that some of the newly synthesized RNA and protein occur in the intact 82S ribosomes and that actinomycin inhibits the low level of protein synthesis provide some indirect evidence for a very low rate of "messenger" synthesis and turnover in zoospores.     

Effects of estradiol on uterine ribonucleic acid metabolism. Assessment of transfer ribonucleic acid methylation.

Immature rats treated with estradiol for selected periods of time demonstrated both increased methylation of uterine transfer ribonucleic acid (tRNA) and methylase activities. Whereas the former parameter was assessed by incubating whole uteri with [methyl-14C]methionine and measuring the incorporation of isotope into the tRNA, methylase activity was obtained by measuring the rate of incorporation of methyl groups from S-adenosyl[methyl-14C]methionine into heterologous tRNA (Escherichia coli B) in the presence of uterine cytosol preparations (100,000g supernatants). Although increased methylation of tRNA during the estrogen response was demonstrated, additional studies indicated that these results were largely attributable to an increased rate of synthesis of tRNA rather than gross changes in either the type or amount of methylated constituents present. Evidence in this regard included the inability of estrogen treatment of alter significantly the (a) resulting patterns of methyl-14C-methylated constituents of uterine tRNA, (b) the extent ot which [2-14C]guanine residues, incorporated into tRNA, become methylated, (c) the extent of methylation of precursor tRNA in the absence of tRNA synthesis, and (d) the types of methylase activities expressed in vitro.     

The effect of castration on the ribonucleic acid metabolism of an experimental prostatic tumour

1. The incorporation of [(14)C]phenylalanine into the protein of microsomes obtained from an androgen-dependent transplantable prostatic tumour has been investigated. 2. The incorporation of [(14)C]ATP into the RNA of the nuclei from the same tumour has also been examined. 3. The castration of the host animal depresses the incorporation of both labelled compounds on subsequent incubation in vitro. 4. The uptake of phenylalanine can be markedly stimulated by polyuridylic acid only in tumours obtained from castrated host animals. 5. The tumour RNA-polymerase activity appears to be dependent on the concentrations of androgens in the host animal.