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At least 1,315 records · Page 73Linked to original sources
PubMed1987

A developmentally regulated activity that unwinds RNA duplexes.

We have attempted to use antisense RNA techniques in the developing Xenopus embryo and found that although hybrids form between sense and antisense RNAs, they are transient. Our studies indicate that this is due to the presence of an activity that unwinds RNA:RNA hybrids. The activity is present at low, but detectable, levels in Xenopus oocytes, increases during oocyte maturation, and exists at high levels throughout early embryogenesis. The activity has been characterized in S100 extracts. The denaturation of a specific RNA:RNA hybrid is inhibited by the addition of a second duplexed RNA but not by the addition of single-stranded RNA, single-stranded DNA, or double-stranded DNA.

Animals↗
PubMed1984

Transcription in vaccinia virus cores. The RNA produced during the first round of transcription does not differ from RNA transcribed in subsequent rounds.

RNA was synthesized in vitro in vaccinia virus cores for times sufficiently short that only the first round of transcription took place. This RNA was compared to RNA synthesized for longer times (which is mainly comprised of reinitiated RNA) by hybridization to fragments of vaccinia virus DNA obtained with several different restriction endonucleases. Under the conditions studied, the composition of mRNA produced during the first round of transcription was the same as that produced in subsequent (reinitiated) rounds. Thus, there is no special arrangement of polymerase molecules within the cores that would allow, in the first round of transcription, for the synthesis of mRNAs distinct from those made in subsequent rounds of transcription. Thus, attachment of polymerase molecules to DNA is likely to occur during preincubation in a way similar to that during reinitiation.

DNA, Viral↗
PubMed1991

Monoaminergic regulation of proopiomelanocortin messenger RNA concentrations in primary cell cultures of rat hypothalamus.

The effect of monoaminergic neurotransmitters on a 1.1-kb proopiomelanocortin messenger RNA (POMC mRNA) detected in rat hypothalamic cells maintained in culture has been evaluated. Serotonin caused a 15% increase in POMC mRNA levels, an effect which was blocked by the 5-HT2 receptor antagonist ketanserin. Dopamine markedly decreased POMC mRNA levels in a dose related manner. Haloperidol and the selective D2 antagonist (+)-butaclamol prevented the inhibitory effects of both dopamine and the selective D2 agonist, 2-bromo-alpha-ergocryptine. The selective dopamine D1 receptor agonist, SKF 38393, as well as norepinephrine and acetylcholine did not affect POMC mRNA levels. It is concluded that serotonin exerts a positive control and dopamine a negative control on POMC mRNA concentrations in primary cultures of rat hypothalamic neurons. The negative effect of dopamine appears to be exerted via D2 receptor-mediated mechanism.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1978

Glucocorticoid regulation of rat thymus RNA polymerase activity: the role of RNA and protein synthesis.

Treatment of rat thymus cells with the glucocorticoids cortisol and dexamethasone resulted in the stimulation of RNA polymerase B activity within 10 min of steroid addition. This early effect was followed by the inhibition of both RNA polymerase A and B activities. These effects were glucocorticoid-specific and were inhibited by the antiglucocorticoid cortexolone. The inhibitory effect of dexamethasone on RNA polymerase A activity was abolished by prior treatment of the cells with alpha-amanitin, cordycepin or cycloheximide, but cycloheximide was only capable of inhibiting the steroid effect measured at 3 h if added within 10--20 min after steroid addition. Cycloheximide had no effect on the steroid-mediated inhibition of RNA polymerase B activity. Control RNA polymerase A activities were unaffected by the presence of inhibitors of RNA and protein synthesis. It is concluded that the inhibition of ribosomal RNA synthesis by glucocorticoids is dependent on protein synthesis, but that basal RNA polymerase A activity in rat thymus cells is not stringently coupled to protein synthesis.

Amanitins↗
PubMed1991

Biphasic regulation of proopiomelanocortin messenger RNA concentrations by corticotropin-releasing factor in primary cultures of rat hypothalamic neurons.

Primary cultures of rat hypothalamic neurons in which a 1.1-kb proopiomelanocortin (POMC) mRNA can be detected, were incubated with corticotropin-releasing factor (CRF) for periods of up to 84 h. A cyclic modulation of POMC mRNA concentrations by CRF was noted. A rapid acute inhibition of POMC mRNA levels after 1 h of exposure was followed by a transient stimulation and then by a more prolonged inhibition which reached a nadir after 48 h.

Animals↗
PubMed2005

Regulating mammalian transcription with RNA.

Recent reports have demonstrated that small duplex RNAs mediate recognition of chromosomal DNA and inhibit transcription within mammalian cells. Key unresolved issues include whether RNAs directly bind to DNA, the identification of the mechanism(s) that convert chromosome recognition into gene silencing and whether naturally occurring antigene RNAs (agRNAs) exist.

Animals↗
PubMed1998

A sequence based computational identification of a Drosophila developmentally regulated TATA-less RNA polymerase II promoter and its experimental validation.

Many RNA polymerase II promoters lack the characteristic TATA box sequence located -25/-30 nucleotides upstream from the transcription start. In Drosophila, half of the promoters identified so far are TATA-deficient. The yemanuclein-alpha gene whose promoter activity is restricted to oogenesis, falls in this class. A number of upstream and downstream promoter elements have been identified for some TATA-less promoters. The yem-alpha promoter contains none of the consensus elements identified so far. Our work was based on the assumption that the physical parameters of the DNA could be used to predict the location of the yem-alpha promoter. A sequence based computational analysis allowed us to determine the characteristic changes of DNA curvature and helix stability in the presumptive regulatory region. Our experimental data were in good agreement with the computational analysis. We have started to investigate the general value of this approach by analyzing other promoters.

Animals↗
PubMed1996

Identification of host factors that regulate the influenza virus RNA polymerase activity.

Transcription and replication of the influenza virus RNA genome take place in the nuclei of infected cells. Ribonucleoprotein (RNP) complexes consisting of viral RNA, RNA polymerase, and nucleocapsid protein (NP) are proven to be the catalytic unit for RNA synthesis, while it has been indicated that the viral RNA polymerase activity is modulated by host-derived nuclear factors. Here we have identified such host factors present in nuclear extracts prepared from uninfected HeLa cells with biochemical complementation assays using the in vitro RNA synthesis system. The stimulatory activity was not absorbed to phosphocellulose but was tightly bound to Q-Sepharose. The eluate recovered from Q-Sepharose was able to stimulate the RNA synthesis catalyzed by both RNP complexes and purified RNA polymerase and NP. The stimulatory activity was further separated into two distinct fractions, designated RAF-1 (RNA polymerase activating factor-1) and RAF-2 fractions, through phenyl-Sepharose column chromatography. When these fractions were fractionated through a gel filtration column, RAF-1 and RAF-2 activities were recovered in fractions corresponding to the molecular mass of 350 kDa and 60 kDa, respectively. Furthermore, the RAF-2 fraction was shown to contain an inhibitory activity, tentatively designated RIF-1 (RNA polymerase inhibitory factor-1). RIF-1 sedimented as fast as bovine serum albumin in glycerol density gradient centrifugation. Roles of these host factors are discussed in the context of viral RNA transcription and replication.

Biological Factors↗
PubMed1996

Estrogen regulation of preproenkephalin messenger RNA in the forebrain of female mice.

We studied the effects of 10 micrograms of 17-beta-estradiol-3-benzoate treatment on preproenkephalin (PPE) mRNA expression in female ovariectomized (OVX) Swiss Webster mice after 0, 1, 6, 12, 24, or 48 h, using the in situ hybridization technique. The VMH showed a 1.6- and 3.3-fold increase in PPE mRNA levels after 24 and 48 h of estrogen treatment (respectively) when compared to OVX females. No differences at 1, 6 or 12 h of estrogen treatment groups were observed compared to control groups. PPE mRNA levels were also increased at 24 and 48 h after estrogen treatment in the posterior medial nucleus of the amygdala (MeAmyg) by 3.3- and 2.5-fold, respectively, and in the arcuate nucleus (ARC) by 2- and 1.9-fold, respectively. No effects of estrogen were observed on PPE mRNA levels in the caudate-putamen (CPu) or the posterior lateral cortical nucleus of the amygdala (plCoAmyg). Furthermore, basal levels of PPE mRNA expression in the VMH and MeAmyg of female mice were lower than those observed in rats, although levels in the CPu, plCoAmyg, and ARC were similar between females of the two species. In conclusion, we have found two differences between the species. First, Swiss mice demonstrated a slower time course of estrogen induction of PPE mRNA in the VMH, ARC. and MeAmyg compared to female rats. Second, there are differences in basal levels of PPE in the MeAmyg and VMH.

Animals↗
PubMed1975

Regulation of casein messenger RNA during the development of the rat mammary gland.

Casein mRNA was isolated and partially purified from RNA extracts of rat lactating mammary glands and translated in a teterologous cell-free protein synthesizing system derived from wheat germ. Casein mRNA activity was assayed by immunoprecipitation using a specific antiserum prepared against a mixture of the purified rat caseins. Properties of rat casein mRNA were examined using a variety of sizing techniques, including chromatography on Sepharose 4B, sedimentation on sucrose gradients after heat denaturation, and electrophoresis on 2.5% agarose gels in 6 M urea. Casein mRNA activity was found in an 8-16S region after gradient centrifugation with the peak occurring at 10.5 S. In addition, the binding of rat casein mRNA to dT-cellulose was examined. Only 40% of the total casein mRNA activity was selectively retained. A partial purification of casein mRNA was accomplished by a combination of these sizing and affinity chromatography techniques. In the purified preparations casein mRNA activity comprises approximately 90% of the total mRNA activity. Characterization of this material by agarose gel electrophoresis revealed two main bands of RNA at approximately 12 and 16 S, both containing casein mRNA activity. These mRNAs were of the correct size to code for two of the principal rat caseins of approximately 25,000 and 42,000 molecular weights. Casein mRNA and total mRNA activities were then compared in total RNA extracts at various stages of normal mammary gland development in the rat, i.e. during pregnancy, lactation, and involution following weaning. A selective induction of casein mRNA activity compared to total mRNA activity was found to occur during pregnancy and lactation. Moreover, a selective loss of activity was also observed during mammary gland involution. A surprisingly high level of casein mRNA activity was found in RNA extracts from early and midpregnant mammary glands.

Animals↗
PubMed1983

Coordinate regulation of unsaturated phospholipid, RNA, and protein synthesis in Mycoplasma capricolum by cholesterol.

The effect of cholesterol, epicoprostanol, and phosphatidylcholine on phospholipid, RNA, and protein synthesis was investigated in the sterol auxotroph Mycoplasma capricolum. Cells growing poorly on lanosterol were stimulated to grow more rapidly by supplementing the medium with either 2 micrograms of cholesterol or 2.2 micrograms of egg phosphatidylcholine per ml. In such cells cholesterol caused a sequential stimulation of phospholipid, RNA, and protein synthesis. Enhanced oleate incorporation into phospholipid occurred early; the rates of RNA and protein synthesis increased later. In cells supplemented with phosphatidylcholine only RNA and protein syntheses were enhanced. The addition of 2 micrograms of epicoprostanol per ml to cells growing on lanosterol promptly inhibited the rate of unsaturated phospholipid synthesis and subsequently the rate of growth. Inhibition of both processes was relieved by supplying 2 micrograms of cholesterol or 2.2 micrograms of phosphatidylcholine per ml along with the inhibitory sterol. The results suggest that cholesterol in small amounts exerts a positive regulatory effect and epicoprostanol exerts a negative one on unsaturated phospholipid synthesis and, in turn, that RNA and protein synthesis are coordinately controlled with phospholipid synthesis. The previously reported phenomenon of sterol synergism and the postulated novel role of sterols in membranes.

Bacterial Proteins↗
PubMed2004

RNA structural rearrangement via unwinding and annealing by the cyanobacterial RNA helicase, CrhR.

Rearrangement of RNA secondary structure is crucial for numerous biological processes. RNA helicases participate in these rearrangements through the unwinding of duplex RNA. We report here that the redox-regulated cyanobacterial RNA helicase, CrhR, is a bona fide RNA helicase possessing both RNA-stimulated ATPase and bidirectional ATP-stimulated RNA helicase activity. The processivity of the unwinding reaction appears to be low, because RNA substrates containing duplex regions of 41 bp are not unwound. CrhR also catalyzes the annealing of complementary RNA into intermolecular duplexes. Uniquely and in contrast to other proteins that perform annealing, the CrhR-catalyzed reactions require ATP hydrolysis. Through a combination of the unwinding and annealing activities, CrhR also catalyzes RNA strand exchange resulting in the formation of RNA secondary structures that are too stable to be resolved by helicase activity. RNA strand exchange most probably occurs through the CrhR-dependent formation and resolution of an RNA branch migration structure. Demonstration that another cyanobacterial RNA helicase, CrhC, does not catalyze annealing indicates that this activity is not a general biochemical characteristic of RNA helicases. Biochemically, CrhR resembles RecA and related proteins that catalyze strand exchange and branch migration on DNA substrates, a characteristic that is reflected in the recently reported structural similarities between these proteins. The data indicate the potential for CrhR to catalyze dynamic RNA secondary structure rearrangements through a combination of RNA helicase and annealing activities.

Base Sequence↗
PubMed2000

Regulation of the RNA-dependent protein kinase by triple helix formation.

The RNA-dependent protein kinase (PKR) is an interferon-induced, RNA-activated enzyme that phos-phorylates the alpha-subunit of the translation initiation factor eIF-2, inhibiting its function. PKR is activated in vitro by binding to double-stranded RNA (dsRNA) molecules of approximately 30 bp or longer. Here we show that triple helix forming oligonucleotides (TFOs) inhibit dsRNA binding to the isolated RNA binding domain of PKR. The inhibition is specific to the targeted RNA and dependent on TFO length. Binding to a 30 bp duplex is inhibited by a 28 nt TFO and a 20 nt TFO with an IC(50) of 35 +/- 2 and 210 +/- 22 nM, respectively. An 18 nt TFO partially inhibits binding. The activation of the kinase domain of PKR by a 30 bp RNA duplex is also inhibited by a 28 nt TFO. Inhibition of binding is most effective when the triple helix is formed prior to addition of the protein. These results indicate that triplex formation can be used to prevent the binding of an RNA binding protein with dsRNA-binding motifs.

Base Sequence↗
PubMed1985

Regulation of uterine nucleolar RNA synthesis by estrogens.

Administration of estradiol to ovariectomized mature rats results in a biphasic early (4 h) and late (24 h) increase in transcriptional activity of isolated uterine nucleoli. The increased rate of nucleolar RNA synthesis is dependent upon the dose of estradiol over the range of 0.1 to 1 micrograms/animal, and exhibits hormone specificity. Administration of cycloheximide, an inhibitor of protein synthesis, prior to the administration of hormone or during the early phase of estrogen action (less than 4 h) blocks the estrogen-induced increase in uterine nucleolar transcriptional activity. Administration of cycloheximide during the later phase (greater than 8 h) of estrogen action is without effect on the estrogen-induced increase in transcriptional activity of isolated uterine nucleoli. This suggests that the longer term maintenance of the hormone-stimulated increase in nucleolar RNA synthesis is independent of continuous protein synthesis. Results indicate that the estrogen-induced accumulation and subsequent decline in uterine nuclear estradiol receptor levels is unaffected by cycloheximide treatment. Together, these results indicate the presence of the receptor-hormone complex in the nucleus is not solely responsible for the increased transcriptional activity of uterine nucleoli following in vivo hormone treatment. The early activation of uterine nucleolar RNA synthesis by estrogen seems to result from the synthesis of a short-lived protein(s) that modified RNA polymerase I and/or the nucleolar chromatin template.

Animals↗