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At least 127 records · Page 7Linked to original sources
PubMed1999

Transcriptional and posttranscriptional regulation of insulin-like growth factor binding protein-3 by cyclic adenosine 3',5'-monophosphate: messenger RNA stabilization is accompanied by decreased binding of a 42-kDa protein to a uridine-rich domain in the 3'-untranslated region.

The Madin Darby bovine kidney (MDBK) cell line was used to investigate the mechanisms underlying the cAMP regulation of insulin-like growth factor binding protein-3 (IGFBP-3) gene expression. Treatment of confluent monolayers either with forskolin or cAMP produced a 60- to 75-fold induction of IGFBP-3 mRNA and protein levels. This effect did not require new protein synthesis as inhibition of translation by cycloheximide actually caused a 2-fold increase in the cAMP induction. The rates of IGFBP-3 gene transcription, assessed by nuclear run-on assays, increased approximately 15-fold in cells exposed to cAMP. In addition, the half-life of the IGFBP-3 mRNA transcript was increased approximately 3-fold in the presence of cAMP. Gel mobility shift and competition experiments revealed the specific binding of an approximately 42-kDa cytoplasmic protein factor to the 3'-untranslated region (3'-UTR) of the IGFBP-3 mRNA. A 21-nucleotide uridine-rich segment that contained no AUUUA motif was sufficient for the specific binding. The binding activity of this protein was reduced after cAMP treatment but was increased by phosphatase treatment. In conclusion, the cAMP induction of IGFBP-3 mRNA in MDBK cells occurred at both the transcriptional and posttranscriptional levels. The IGFBP-3 mRNA stabilization in MDBK cells probably involved the phosphorylation of a member of the family of U-rich region mRNA-binding proteins and is the first reported member whose RNA-binding activity is reduced by cAMP.

3' Untranslated Regions↗
PubMed1988

Autogenous regulation of tubulin synthesis via RNA stability during sea urchin embryogenesis.

When pluteus embryos of Lytechinus pictus were treated with colcemid, the incorporation of [35S]methionine into tubulin declined by 5- to 15-fold within 4 h. This was mostly accounted for by a rapid decline in the concentration of alpha- and beta-tubulin mRNA in the cytoplasm. Treatment with other microtubule depolymerizing agents (colchicine, nocodazole, low concentrations of vinblastine) had similar effects. Treatment of embryos with the microtubule-stabilizing agent, taxol, or high concentrations of vinblastine resulted in increased synthesis of tubulin. The concentration of tubulin mRNA increases during development and becomes increasingly sensitive to colcemid and decreasingly sensitive to taxol. The transcriptional activity of tubulin genes, estimated by an RNA run-on assay in isolated nuclei, was not altered after colcemid treatment. On the other hand, the rate of decay of tubulin mRNA in prism embryos treated with actinomycin D was increased several fold by colcemid treatment, while taxol treatment led to an increased half-life of tubulin mRNA. These observations suggest that tubulin synthesis is autogenously regulated at the level of mRNA stability by the level of unpolymerized tubulin. The increasing polymerization of microtubules and declining level of unpolymerized tubulin during embryogenesis would result in a stabilization of tubulin mRNA accounting for the increasing concentration of tubulin mRNA and rate of tubulin synthesis, as well as the increasing sensitivity of tubulin synthesis to microtubule-depolymerizing agents. Evidence is also presented for a rapid influence of the level of unpolymerized tubulin on the efficiency of translation of tubulin mRNA.

Alkaloids↗
PubMed1991

Messenger RNA stabilization in chicken lens development: a reexamination.

Previous studies, using actinomycin D, suggested that the rate of mRNA degradation in chicken embryo lens epithelial cells decreased sharply between Days 11 and 13 of development (Yoshida and Katoh, Exp. Eye Res. 11, 1971; Exp. Cell Res. 71, 1972). We repeated these studies and directly measured the effects of actinomycin on lens mRNAs. Although actinomycin decreased [3H]uridine incorporation greater than 90%, only modest decreases in methionine incorporation were detected. Treatment for 6 hr had no detectable effect on delta-crystallin mRNA levels or on the relative amounts of proteins synthesized in an in vitro translation system. Unlike the previous studies, we did not find significant changes in the stability of lens epithelial mRNAs during development.

Animals↗
PubMed1995

Lactate dehydrogenase A subunit messenger RNA stability is synergistically regulated via the protein kinase A and C signal transduction pathways.

We have identified and studied a posttranscriptional mechanism of lactate dehydrogenase A (LDH) subunit gene expression at the level of mRNA stability. Using the well differentiated rat C6 glioma cell line as a model system, the effects of activators of the protein kinase A and C pathways on the half-life of LDH A mRNA were measured by two independent methods: 1) by the RNA synthesis inhibitor-chase method using actinomycin D, and 2) by analysis of decay of LDH A [3H]mRNA in [3H]uridine-labeled cells. By each method, the half-life of relatively short-lived LDH A mRNA was increased 5- to 7-fold in 8- (4-chloro-phenylthio) cAMP or forskolin-treated and about 3-fold in 12-0-tetradecanoylphorbol-13- acetate (TPA) or dioctanoylglycerol-treated cells. Forskolin acted synergistically with TPA to prolong LDH A mRNA half-life from 55 min to more than 20 h. The relatively rapid basal decay rate of LDH A mRNA was also considerably slowed in the presence of the protein phosphatase inhibitor okadaic acid, suggesting a functional role for protein phosphorylation in the stabilization process. In glioma cells stably transformed with a protein kinase A catalytic subunit expression vector, overexpression of the catalytic subunit stabilized LDH mRNA to the degree seen in forskolin-treated cells. In cells transfected with a protein kinase A inhibitor-expression vector, cAMP-mediated stabilization of LDH A mRNA half-life was prevented. Furthermore, both staurosporin and 3- [1-(3-dimethylaminopropyl)-indol-3-yl]-3-(indol- 3-yl)- maleimide, inhibitors of protein kinase C, prevented the TPA-induced stabilization of LDH A mRNA. We conclude from the experimental data that the protein kinase A and C signal pathways play an active functional role in regulating LDH A mRNA stability and act cooperatively to achieve LDH A mRNA stability regulation.

Animals↗
PubMed1971

New polarity suppressors in Escherichia coli: suppression and messenger RNA stability.

Two new polarity suppressors (Su27 and Su78) have been isolated in Escherichia coli. Both suppress polarity in the trp and lac operons, and neither shows codon specificity for suppression. Extreme polar mutants of the lac z gene that contain either Su27 or Su78 make mRNA from the entire operon; however, no active beta-galactosidase is translated from the z-gene messenger, and the amount of distal messenger is greater than would be expected from corresponding enzyme activities. Puromycin treatment of lac(+) strains mimics the effect of polar chain-termination mutations in destabilizing lac mRNA. This effect is completely reversed by Su27, and it is partially reversed by Su78. The results suggest that these suppressors act by stabilizing mRNA after premature termination of protein synthesis.

Acyltransferases↗
PubMed1999

Regulation by p38 mitogen-activated protein kinase of adenylate- and uridylate-rich element-mediated urokinase-type plasminogen activator (uPA) messenger RNA stability and uPA-dependent in vitro cell invasion.

MDA-MB-231 cells are highly metastatic breast tumor cells. Their high invasiveness is thought to be due to constitutively high levels of urokinase-type plasminogen activator (uPA) and its receptor. Previously (R. Nanbu et al., C. Eur. J. Biochem., 247: 169-174, 1997), we showed that uPA mRNA in these cells is stable and that mRNA degradation mediated by an AU-rich element (ARE) is impaired. Here we report that treatment of MDA-MB-231 cells with SB203580, an inhibitor of the stress-activated p38 mitogen-activated protein (MAP) kinase, strongly destabilized uPA mRNA in an ARE-dependent manner. In contrast, in LLC-PK1 and HeLa cells, uPA mRNA is unstable, and an ARE present in the 3' untranslated region plays a role in its degradation. Enhanced ARE-mediated mRNA destabilization induced by SB203580 was also observed in both LLC-PK1 and HeLa cells with a globin chimeric mRNA harboring two copies of the ARE (globin-2ARE) from uPA mRNA. Overexpression of constitutively active MKK6, a p38 upstream activator kinase, increased the stability of the globin-2ARE message in LLC-PK1 cells, confirming the participation of p38 in the regulation of ARE-mediated mRNA decay. Interestingly, the half-life of the uPA mRNA in the three cell lines studied correlated with the basal levels of active p38. SB203580 treatment of MDA-MB-231 cells decreased cell-associated uPA activity and dramatically reduced in vitro cell invasiveness. These results suggest the participation of p38 in the control of invasiveness through regulation of the stability of uPA and uPA receptor mRNA, which is also destabilized by p38.

3' Untranslated Regions↗
PubMed1996

G.A and U.U mismatches can stabilize RNA internal loops of three nucleotides.

Optical melting experiments on oligoribonucleotides containing internal loops of three nucleotides (two nucleotides opposing one nucleotide) flanked by CG pairs show that the free energy of internal loop formation depends on the sequence of nucleotides within the loop. Internal loops with the potential for A.G and U.U mismatch pairing generally have more favorable free energies of formation than internal loops with potential AA, CC, AC, or UC pairings. In most cases, potential A.G and U.U pairings leaving a single unpaired nucleotide 5' to a flanking CG pair are most stable; those leaving a single nucleotide 3' to a flanking CG pair have intermediate stability. Internal loops of three nucleotides without potential A.G or U.U pairs are the least stable. The results provide an improved model for predicting the folding stabilities of internal loops of three nucleotides.

Adenine↗
PubMed1999

Messenger RNA stability and its role in control of gene expression in bacteria and phages.

The stability of mRNA in prokaryotes depends on multiple factors and it has not yet been possible to describe the process of mRNA degradation in terms of a unique pathway. However, important advances have been made in the past 10 years with the characterization of the cis-acting RNA elements and the trans-acting cellular proteins that control mRNA decay. The trans-acting proteins are mainly four nucleases, two endo- (RNase E and RNase III) and two exonucleases (PNPase and RNase II), and poly(A) polymerase. RNase E and PNPase are found in a multienzyme complex called the degradosome. In addition to the host nucleases, phage T4 encodes a specific endonuclease called RegB. The cis-acting elements that protect mRNA from degradation are stable stem-loops at the 5' end of the transcript and terminators or REP sequences at their 3' end. The rate-limiting step in mRNA decay is usually an initial endonucleolytic cleavage that often occurs at the 5' extremity. This initial step is followed by directional 3' to 5' degradation by the two exonucleases. Several examples, reviewed here, indicate that mRNA degradation is an important step at which gene expression can be controlled. This regulation can be either global, as in the case of growth rate-dependent control, or specific, in response to changes in the environmental conditions.

Bacteria↗
PubMed1997

X chromosome inactivation is mediated by Xist RNA stabilization.

Low level Xist expression can be detected from both active X chromosomes (Xa) in female embryonic stem cells prior to X inactivation. After differentiation, Xist is expressed at high levels only from the inactive X chromosome (Xi). Differentiating female cells increase Xist expression from the Xi prior to silencing low level Xist expression from the Xa. The transition from low level to high level expression is regulated by the stabilization of Xist transcripts at the Xi. We suggest that these developmentally modulated changes in Xist expression are regulated by several different mechanisms: factors that stabilize Xist transcripts at the Xi, an activity that blocks this stabilization at the Xa, and a mechanism that silences low level Xist expression from the Xa.

Animals↗
PubMed1998

Increased P-glycoprotein messenger RNA stability in rat liver tumors in vivo.

P-glycoproteins (Pgp) are comprised of a small family of plasma membrane proteins whose abundance in cultured cells is often associated with the multidrug resistance phenotype. Overexpression of Pgp has been observed in many types of human cancers, but the molecular basis for this overexpression has not been established. We have used primary monolayer cultures of adult rat hepatocytes and a stepwise model of rat liver carcinogenesis to study the regulation of Pgp gene expression. We observed a marked overexpression of Pgp, specifically the class II Pgp, in both systems. In addition, we observed that a number of unrelated genes including alpha-tubulin, beta-actin, gamma-actin, cytokeratin 8, cytokeratin 18, and c-myc are overexpressed in cultured hepatocytes, and they are also overexpressed during liver carcinogenesis and in transplantable tumors. Nuclear run-on assays showed no increase in the transcriptional activity of Pgp genes in transplantable liver tumors compared to normal liver. Studies of in vivo mRNA stability, however, revealed that all three Pgp mRNAs were relatively stable in transplantable liver tumors (t(1/2) > 12 h), in contrast to what was found in normal liver (t(1/2) < 2 h). In addition, mRNA for several other genes, including alpha-tubulin, c-myc, and cyclin D1, all appear to be stabilized in the tumors. These findings suggest that the overexpression of Pgp genes in rat liver tumors may be the result of a mechanism involving stabilization of a diverse group of mRNAs.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1988

Defective T lymphocytes in old mice. Diminished production of mature c-myc RNA after mitogen exposure not attributable to alterations in transcription or RNA stability.

To gain further insight into the mechanism of age-associated loss of T cell proliferative responses to mitogenic lectins, we measured c-myc specific mRNA accumulation in Con A-stimulated cultures of spleen cells from old and young mice using Northern blot and S1 nuclease protection analyses. Aging led to a consistent decline (an average of approximately 60%) in the level of c-myc mRNA in stimulated cells. The time course for c-myc RNA accumulation was similar for old and young mice. Nuclear runoff experiments showed that mitogen stimulation leads to an equivalent increase in transcription of the c-myc gene in T cells from old and young mice. Furthermore, in the presence of 5,6-dichlorobenzimidazole riboside, a selective inhibitor of RNA polymerase II, c-myc mRNA decayed with equal kinetics in cells from mice of different ages. These results show that lymphocytes from aged mice exhibit defects in gene expression very early in the activation process and suggest that these deficits may involve, at least for some genes, alterations in post-transcriptional processing.

Aging↗