Adenine-rich polymer associated with rabbit reticulocyte messenger RNA

The metabolism of high-molecular-weight ribonucleic acid in hypothalamic and cortical regions of the developing female rat brain

The regional metabolism of high-molecular-weight RNA in the developing female rat brain was investigated after the intracranial injection of [32P]P1. The synthesis of polyadenylated RNA relative to high-molecular-weight RNA was determined after oligo(dT)-cellulose chromatography of total cellular high-molecular-weight RNA labelled after 4h. In both hypothalamus and cortex this synthesis was significantly higher during the first 10 days post partum than at subsequent ages. In both regions apparently more mRNA is synthesized in the young. The ratio of the specific radioactivity of cytoplasmic high-molecular-weight RNA relative to that of the nucleus, measured after a 48 h period of labelling, was considered to be an index of the nucleocytoplasmic transport of newly synthesized RNA [Berthold & Lim (1976) Biochem. J. 154, 529--539]. In the cortex, nucleo-cytoplasmic RNA transport in rats aged up to 20 days was significantly higher than in older rats, with the maximal value being attained between 16 and 19 days post partum. In contrast, in the hypothalamus, nucleo-cytoplasmic transport of RNA was low during the neonatal period and comparable with that of the mature animal. However, there were two periods of increased transport at later stages of development, the first between 15 and 19 days post partum and the second between 25 and 29 days post partum. These prepubertal changes in the nucleo-cytoplasmic transport of RNA in the female hypothalamus during weeks 3 and 4 post partum are coincident with other reported changes occurring during sexual differentiation. Differences in the timing of the maturational changes of the two brain regions thus appear to be reflected in developmental changes in RNA transport.

Poly(A) polymerases of rat liver nuclei. Purification and specificity

Two poly(A) polymerases were isolated from rat liver nuclei and purified more than one thousand times by ion exchange chromatography on DEAE-Sephadex and phosphocellulose columns as well as affinity chromatography on a chromosomal RNA-Sepharose column. One of the two enzymes is bound to chromatin and uses as primer chromosomal RNA, while the second one is localized in the nucleoplasm and uses as primer poly(A) and hnRNA isolated from chromatin. The two enzymes seem to participate in the polyadenylation of chromosomal RNA in vitro, by a coupled mechanism. According to this mechanism, the chromatin bound enzyme adds 120-130 adenosine nucleotides to chromosomal RNA and consequently the nucleoplasmic enzyme completes the poly-adenylation by adding 80-90 more AMP units to the polyadenylated end of chromosomal RNA.

Sequence complexity and relative abundance of vaccinia virus mRNA's synthesized in vivo and in vitro

The sequence complexity and relative abundance of vaccinia virus mRNA's, synthesized in vivo and in vitro, have been measured by DNA-RNA hybridization. Up to 42% of [3H]thymidine-labeled virus DNA can be protected from digestion with nuclease S1, a single-strand specific nuclease, after annealing to excess polyadenylylated mRNA obtained at 7 h after infection. In contrast, only 26% of vaccinia virus DNA is protected when hybridized to polyadenylylated RNA obtained at 2 h after infection in the presence of an inhibitor of DNA synthesis. That the 94 kilobases transcribed early are a subset of the 152 kilobases present late was suggested by hybridization of DNA with a mixture of early and late RNAs. Some control of transcription is lost when virus purified by procedures that include sonic treatment is used for infection since under these conditions similar proportions of DNA are protected by either excess early or late RNA. Excess RNA, synthesized in vitro by enzymes within purified vaccinia virus particles, hybridized to approximately the same fraction of the DNA as did RNA present at late times in vivo. A second type of transcriptional control was demonstrated by kinetic analysis of the hybridization of polyadenylylated RNA to labeled DNA. With virion DNA used as the probe, a single abundance class for early RNA, two classes differing 11-fold in abundance for late RNA, and two classes differing 43-fold in abundance for in vitro RNA were found. To be able to detect high-abundance RNAs of very low sequence complexity, labeled complementary DNA probes to early, late, and in vitro polyadenylylated RNA were used. Evidence that, at late times, RNAs totaling 9 kilobases of sequence complexity are present 40 to 500 times more frequently than the bulk of the virus-specific RNA was obtained. In contrast, the highest abundance class of RNA present at 2 h after infection corresponded to 7 kilobases present in only a 13-fold molar excess over the majority of virus-specific sequences. RNA synthesized in vitro was found to contain a small amount of sequence information, approximately 2 kilobases, which occurred 150 times more frequently than the majority of viral sequences. Studies using hybridization of viral DNA to labeled complementary DNA probes also suggested that 52 to 59% of the polyadenylylated RNA present at 2 h after infection and 82 to 92% of that at 7 h are virus specific.

Poly(A) polymerase activity during cell cycle and erythropoietic differentiation in erythroleukemic mouse spleen cells

Poly(A) polymerase activity was studied in lysates of cultured murine erythroleukemic cells (Friend cells). Incorporation of ATP into acid-precipitable products is dependendent on the presence of Mn2+ or Mg2+ and of an RNA primer. The reaction is specific for ATP as the substrate (KM=290 290 micron, it is not inhibited by actinomycin D and only slightly interferred with by ethidium bromide. Cordycepin 5'-triphosphate and sodium pyrophosphate inhibit the enzyme activity. The chain length of the products of the reaction is dependent on the primer concentration and reaches up to 30 nucleotides. Poly(A) polymerase activity is low in resting (G1 phase) cells 75 nmol ATP incorporated/h per 10(6) cells) and increases to a level about twice as high in early S phase of the cell cycle. A possible model for regulation of enzyme activity is discussed. Polymerase activity in the early phase of erythropoietic differentiation of the cells induced by butyric acid does not show any difference in comparison to untreated controls. A decrease in enzyme activity to levels characteristic for cells in G1 phase accompanies shutdown of cell growth in the course of the ongoing differentiation. Analysis of the DNA content of the cells revealed that erythropoietic differentiation of Friend cells induced by butyric acid is characterized by arrest of the cells in G1 phase of the cell cycle. Poly(A) polymerase activity in erythroleukemic cells is thus controlled only by the phase of the cell cycle; it is not affected by changes in gene expression during erythroid differentiation.

Size and distribution of polyadenylic acid sequences in Drosophila polytene DNA and RNA

[3H]Poly(U) hybridizes very rapidly to polytene DNA from Drosophila hydei. When hybridization is performed at 30 degrees C in 2 X SSC to a large excess of DNA, 95% of the poly(U) becomes ribonuclease resistant. Also, complementary RNA transcribed in vitro from polytene DNA hybridizes to poly(U). 023--0.25% of the DNA is composed of (dA)-rich sequences and 0.23--0.31% of cRNA hybridizes to [3H]poly(U). The length of the (dA)-rich sequences on the DNA and cRNA is 40 nucleotides. The Tm values of these hybrids formed between DNA or cRNA-poly(U) is 45 degrees C. The poly(A) fragments from cytoplasmic RNA ranged from 80 to 170 nucleotides in lenght, and migrated in polyacrilamide gels as a broad peak. The average sizes of the poly(A) fragments from the poly(A)-containing RNA transcribed by nuclei isolated from salivary glands in vivo or in vitro were 40, 70, 170 and 70 nucleotides, respectively. Hybridization in situ of [3H]-poly(U) to chromosome squashes indicated that the (dA)-rich sequences are randomly distributed over the whole genome.

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.

Complete 3' noncoding region sequences of rabbit and human beta-globin messenger RNAs

The 3' noncoding regions of rabbit and human beta-globin mRNAs, 95 and 134 nucleotides in length, have been sequenced. Furthermore, these and previous studies (Baralle, 1977; Proudfoot, 1976a, 1976b) have established about one half of the 589 nucleotide sequence of rabbit beta-globin mRNA, including all of the noncoding region. These sequence studies took advantage of the plus and minus gel-sequencing procedure originally described by Sanger and Coulson (1975) and recently adapted by G.G. Brownlee and E.M. Cartwright (manuscript in preparation). The human and rabbit 3' noncoding region sequences are extensively homologous, except that the human sequence has an addition of 39 nucleotides as compared with rabbit. This extra sequence may have arisen by gene duplication.

Biochemical characterization of RNA and protein synthesis in erythrocyte development

Newts (Triturus cristatus) made anemic with acetylphenylhydrazine (APH) fail to regenerate erythrocytes (RBC's) immediately and exhibit a latent period of 1.5-2 wk during which animals lack RBC's and are aplastic. With the establishment of erythroid regeneration at 10-14 days, relatively homogeneous populations of successive erythropoietic stages occur in the blood. This feature makes possible biochemical analyses of events in early, intermediate, and late developmental stages, respectively, each of which can be obtained in vivo with minimal contamination by other stages. Previous studies have described a primitive cell population referred to as "erythroid precursor cells" (EPC's) which precedes the appearance of definitive erythroid elements. The present studies show that EPC's and early erythroid cells are engaged mainly in ribosomal production, including synthesis of rRNA and ribosomal proteins. Moreover, EPC's and early erythroid cells also synthesize tRNA and a presumed Hb-mRNA which has been identified by its sedimentation rate at 9-12 s and its content of polyadenylic acid. In intermediate stages, there occurs a fourfold decrease in the level of RNA synthesis and, while rRNA continues to be formed, there is a disproportionate accumulation of the two major cytoplasmic rRNA species in favor of the large ribosomal subunit RNA. In late developmental stages, the level of RNA synthesis is markedly diminished with little or no evidence of formation of defined RNA classes. Correlated radioautographic and biochemical studies with radioactive delta-aminolevulinic acid and leucine indicate that EPC's and other early erythroid elements synthesize not only hemoglobin but also ferritin and ribosomal proteins. It is concluded that: (a) erythroid RNA synthesis is most pronounced in the early developmental stages, being manifested predominantly by rRNA production but including tRNA and Hb-mRNA; (b) intermediate developmental stages show both "ribosomal wastage" and decreased growth rate, marking a pivotal point between the transcriptional activities of early stages and translational activities of late stages; (c) EPC's represent a cell population already committed to RBC formation and are excluded from a role as the pluripotential stem cell.

Messenger ribonucleoprotein complexes of cryptobiotic embryos of Artemia salina

Poly(A)-containing ribonucleoprotein (poly(A)+-RNP) particles in the post-mitochondrial supernatant of cryptobiotic embryos of Artemia salina were characterized by hybridization to [3H]-poly(U). By sucrose isopycnic centrifugation, approximately 2/3 of poly(A)+-RNPs was found to band at 1.27-1.30 (g/cm3) and the rest 1+/3 at 1.20-1.23 (g/cm3) and below 1.20 (g/cm3). The 1.27-1.30 RNPs could be separated into two density classes, 1.27-1.28 and 1.30 (g/cm3) respectively. The latter RNP class was apparently complexed with ribosomal components because they were completely converted to the former RNP class (free RNPs) by 25 mM EDTA treatment. Further, the 1.30 (g/cm3) RNPs were resolved into several RNP species having sedimentation coefficients above 50 S. which were transformed mostly to 20-30 S rnps in the presence of 25 mM EDTA. The free 20-30 S RNPs contained 8-14 S poly(A)+-RNAs, having the highest template activity in a wheat embryo cell-free system, whereas the 1.20-1.23 poly(A)+-RNPs consisted of 10 S and 16 S RNPs, both of which contained 4 S poly(A)-containing sequences without any template activity.

A specific polyadenylase from Escherichia coli K12

A polyadenylase, degrading specifically poly(A) sequences was isolated from Escherichia coli K12. The enzyme was purified about 850 times to practically electrophoretic homogeneity. It was free of poly(A) polymerase activity, as well as of the well known E. coli RNAases I and II. It is stimulated by bivalent cations like Mg2+ and Mn2+ and splits poly(A) to 3'-AMP and therefore it can be considered as an exonuclease. The enzyme does not degrade any other ribohomopolymer or RNA.

Endoribonuclease IV. 2. Further investigation on the specificity

The poly(A)-specific endoribonuclease IV produces oligo(A) fragments of a chain length of 10 AMP nucleotides. One enzyme molecule performs 1700 cleavages per min; the cleavages occur randomly. The endoribonuclease IV is a nuclear enzyme which is present in the oviduct of quails in a concentration of 40 000 enzyme molecules per cell. Poly(A) segments on mRNA are selectively hydrolyzed by endoribonuclease IV; the poly(A)-free part of the RNA is not affected. After incubation with the enzyme, a residual oligo(A) stretch of 5 AMP nucleotides remains on poly(A)-rich RNA. The endoribonuclease IV does not disintegrate the polyribosomal complex after incubation in vitro and the enzyme has also no influence on the translational capacity of a cell-free protein-synthesizing system.

Globin messenger RNA from anaemic rabbit spleen. Size of its polyadenylate segment

The size of the polyadenylate segment of globin messenger RNA isolated from spleens of anaemic rabbits was estimated by comparison of its electrophoretic migration in polyacrylamide gels to that of synthetic poly(A) segments of known lengths. Conditions of enzymic degradation of mRNA with pancreatic ribonuclease and T1 ribonuclease were carefully established in order to ensure complete degradation of the heteropolymeric part of mRNA without affecting the polyadenylate sequence. The poly (A) segments of spleen globin mRNA were found to be 25-90 nucleotides long whilst those of peripheral blood reticulocytes from the same animals were only 10-30 residues long. Since spleen contains young erythroid cells and since anucleated blood reticulocytes constitute a statistically older population of the same cell line, these results support the idea that the poly(A) segment of mRNA shortens when the message ages.

The conservation of poly-A-containing RNA during the dormant state of the moss Polytrichum commune

The moss Polytrichum commune can be dried to less than 2% of free water and kept for some weeks without losing its viability. Upon rehydration of the moss, protein synthesis starts about 60 minutes before incorporation of radioactive precursors into RNA can be observed. Pulse labeled total RNA and poly-A-containing RNA do not show quantitative or qualitative alterations during desiccation up to 20 days.

Poly(A) associated RNA from mitochondria and microsomes of rat brain

Rat brain mitochondria contain a significant proportion of poly(A) associated RNA which is higher than that found in microsomes from the same source. When steady state poly(A) RNA of brain mitochondria was analyzed by microelectrophoresis, it displayed a characteristic separation pattern with a large amount of "free" poly(A).

The formation of poly A-containing RNA in rat liver after administration of 3-methylcholanthrene

The incorporation of [32P] orthophosphate into liver poly A-rich cytoplasmic RNA was investigated in rats which were pretreated with 3-methyl cholanthrene (3MC) or with the vehicle, corn oil. This incorporation was markedly increased within 6 h after administration of the polycyclic hydrocarbon and reached a maximum by 24 h, i.e., 33-fold increase. The poly A-rich RNA fraction was examined by gel electrophoresis and the specific activity of individual species was shown to be elevated.

Polyadenylate polymerase from cytoplasm and nuclei of N.I.H.-Swiss mouse embryos

Poly (A) polymerase activity from cytoplasm and nuclei of 12-16-day-old mouse embryos has been partially purified by (NH4)2SO4 fractionation, DEAE-cellulose, phosphocellulose and tRNA-Sepharose affinity chromatography, and their properties have been compared. The nuclear and cytoplasmic enzymes exhibit similar chromatographic elution profiles, and similar biochemical and physical properties. Poly(A) polymerase has an absolute requirement for a divalent cation, ATP and an oligo- or polyribonucleotide primer. With tRNA, the divalent salt concentrations for optimum enzyme activity are 1 mM MnCl2 or 10 mM MgCl2. The enzyme activity with MnCl2 is 10-15-fold higher than that with MgCl2. The molecular weight of the native enzyme is about 65 000 and its sedimentation coefficient is around 4.5 S. The average chain length synthesized by the enzyme is between 10 and 13 nucleotides. The inhibitors of RNA polymerase do not affect poly (A) polymerase activity; however, some synthetic rifamycin SV derivatives are potent inhibitors of this enzyme.

The metabolism of high-molecular-weight ribonucleic acid including polyadenylated species, in the developing rat brain

High-molecular-weight RNA was isolated from rat brain at various times after the intracranial administration of [32P]Pi. The synthesis of 28S and 18S rRNA could be detected within 1h of the injection of the radioactive precursor and appeared to be more pronounced, relative to other high-molecular-weight RNA, in the brains of older rats compared with those of newborn rats. Polyadenylated RNA, representing most mRNA and their precursors, was isolated by chromatography on oligo(dT)-cellulose. The contribution of this polyadenylated RNA to total RNA synthesis was investigated in the cerebral cortex and the phylogenetically older brain stem at different stages in the development of the rats by using a 5h period of labelling as an arbitrary index of transcription. In the brain stem the proportion of labelled polyadenylated RNA comprised 27-30% of the total RNA. The corresponding values for the cortex decreased from 34% in newborn rats to 23% in 40-150-day-old rats. These data indicated that proportionately more polyadenylated RNA is synthesized in the cortex of the newborn than in the adult rat and that there is a progressive decrease in the synthesis of polyadenylated RNA relative to rRNA during development.

Nucleo-cytoplasmic relationships of high-molecular-weight ribonucleic acid, including polyadenylated species, in the developing rat brain

The metabolism of high-molecular-weight RNA in the nuclear and cytoplasmic fractions of newborn and adult rat brain was investigated after the intracranial administration of [32P]Pi. In young brain, a considerable proportion of the newly synthesized radioactive RNA is transferred to the cytoplasm, in contrast with the adult brain, where there appears to be a high intranuclear turnover. Electrophoretic analysis of the newly synthesized RNA showed that processing of the rRNA precursor to yield the 28S and 18S rRNA may be more rapid in the adult than in the young, although most of the adult rRNA in the nucleus is not transferred to the cytoplasm. In young brain, processing is probably tightly coupled to transport of rRNA into the cytoplasm, so that 28S and 18S rRNA are not subjected to possible degradation within the nucleus. Polyadenylated RNA turns over in concert with high-molecular-weight RNA in the nuclei of the adult rat brain. In the cytoplasm the polyadenylated RNA has a higher turnover rate relative to rRNA. In the young brain the polyadenylated RNA is transferred to the cytoplasm along with rRNA, although polyadenylated RNA is transported into the cytoplasm at a faster rate. The nuclear and cytoplasmic polyadenylated RNA species of young brain are larger than their corresponding adult counterparts. These results suggest that there are considerable changes in the regulation of the nucleo-cytoplasmic relationship of rRNA and polyadenylated RNA during the transition of the brain from a developing replicative phase to an adult differentiated and non-dividing state.

Study of messenger-like RNA extracted from HeLa cells polysomes. II. Identification of the types of RNA eluted from methylated albumin kieselguhr columns

Together with the elution pattern of pure messenger RNA molecules of various origin, the labelling kinetics of rapidly labelled heterogeneously sedimenting RNA (HSRNA) extracted from polysomes of HeLa cells have been studied by chromatogrphy on columns made of methylated bovine serum albumin adsorbed on kieselguhr. HSRNA is eluted within three peaks-IP, Q2P and TDP-following in that order the increase of NaC1 concentration in the eluting buffer. Besides peak TDP which results from an experimental artefact, our data suggest that the appearance of peaks IP and Q2P reflects the absence and presence respectively of polyadenylic acid stretches in these molecules. Within peak Q2P, the critical factor affecting the order of elution is the size of the polyadenylic acid stretch.

Pattern of labelling of poly (A)-associated RNA in the CA3 region of rat hippocampus during training

Newly synthesized poly (A)-associated mRNA was analysed in the hippocampal CA3 pyramidal nerve cells in rats subjected to training to reverse handedness. The nerve cells of trained animals showed a smaller percentage of poly(A)-associated mRNA than did the active controls. However, a specific fraction of this poly (A) hippocampal RNA with a SE value of around 25 was reproducibly stimulated. This qualitative nerve cell mRNA change is discussed in relation to similar changes in the protein pattern as a function of training.

A micro-method for the assay of polyadenylate-containing ribonucleic acid by gel electrophoresis

A micro-method for the determination of the electrophoretic profile of the various poly(A)-containing RNA species in a RNA sample was developed. The method is simple to carry out and allows for great reproducibility. It combines the resolving power of electrophoresis in agarose with the specificity of binding of poly(A) to poly(U)-containing glass-fibre filters. It consists of the following steps. (1) The molecules in an RNA sample are first separated according to their molecular weight by electrophoresis in agarose, at low ionic strength. 2. The molecules thus seperated are then submitted to a second electrophoresis in 'binding buffer' in a direction perpendicular to the first one. In the course of this electrophoresis the poly(A)-containing RNA species are seperated from other RNA species as they bind to a poly(U)-containing glass-fibre filter which is placed across the electrophoresis path. The method was used to determine the electrophoretic profile of Rhynchosciara salivary-gland messenger RNA. It was found that the population of messenger RNA in the gland is dominated by forms moving as 18 and 158 S peaks, but there is also polydisperse RNA with slower mobility.

Precursor mRNA from erythroid-enriched bone-marrow cells of the rabbit. Electron microscope investigation of precursor mRNA molecules, molecular weight about 1.7 X 10(7), containing mRNA-like structures at one end

Precursor mRNA (pre-mRNA) molecules, sedimenting at greater than 45 S, from erythroid-enriched bone marrow cells of the rabbit and hemoglobin mRNA molecules from rabbit reticulocytes were investigated by electron microscopy. Four of 98 measured pre-mRNA molecules had a length between 15 and 17.1 mum. In some of the pre-mRNA molecules a characteristic condensed structure was observed at one end, strikingly resembling the structure of the mRNA molecules.