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At least 541 records · Page 30Linked to original sources
PubMed1996

Control of transcription termination in prokaryotes.

A growing number of genetic systems have been shown to be controlled at the level of premature termination of transcription. Genes in this class contain transcription termination signals in the region upstream of the coding sequence. The activity of these regulatory termination signals is controlled through a variety of mechanisms. These include modification of RNA polymerase to a terminator-resistant, or terminator-prone form, and alterations in the structure of the nascent transcript, to determine whether the stem-loop structure of an intrinsic terminator or an alternate antiterminator is formed. Structural alterations in the transcript can be controlled by the kinetics of translation of the RNA, by binding of specific regulatory proteins, and by mRNA-tRNA interactions. This review describes a number of variations on the termination control theme that have been uncovered in prokaryotes.

Nucleic Acid Conformation↗
PubMed2006

Regulation of Th2 differentiation and Il4 locus accessibility.

Helper T cells coordinate immune responses through the production of cytokines. Th2 cells express the closely linked Il4, Il13, and Il5 cytokine genes, whereas these same genes are silenced in the Th1 lineage. The Th1/Th2 lineage choice has become a textbook example for the regulation of cell differentiation, and recent discoveries have further refined and expanded our understanding of how Th2 differentiation is initiated and reinforced by signals from antigen-presenting cells and cytokine-driven feedback loops. Epigenetic changes that stabilize the active or silent state of the Il4 locus in differentiating helper T cells have been a major focus of recent research. Overall, the field is progressing toward an integrated model of the signaling and transcription factor networks, cis-regulatory elements, epigenetic modifications, and RNA interference mechanisms that converge to determine the lineage fate and gene expression patterns of differentiating helper T cells.

Animals↗
PubMed2005

Identification of a molecular signature of sarcopenia.

Investigating the molecular mechanisms underlying sarcopenia in humans with the use of microarrays has been complicated by low sample size and the variability inherent in human gene expression profiles. We have conducted a study using Affymetrix GeneChips to identify a molecular signature of aged skeletal muscle. The molecular signature was defined as the set of expressed genes that best distinguished the vastus lateralis muscle of young (n = 10) and older (n = 12) male subjects, when a k-nearest neighbor supervised classification method was used in conjunction with a signal-to-noise ratio gene selection method and a holdout cross-validation procedure. The age-specific expression signature was comprised of 45 genes; 27 were upregulated and 18 were downregulated. This signature also correctly classified 75% of the muscle samples from young and older subjects published by an independent laboratory, based on their expression profiles. The signature revealed increased expression of several genes involved in mediating cellular responses to inflammation and apoptosis, including complement component C1QA, Galectin-1, C/EBP-beta, and FOXO3A, among others. The increased expressions of genes that regulate pre-mRNA splicing, localization, and modification of RNA comprise markers of the aging signature. Downregulated genes in the signature were the glutamine transporter SLC38A1, a TRAF-6 inhibitory zinc finger protein, and membrane-bound transcription factor protease S2P, among others. The sarcopenia signature developed here will be useful as a molecular model to judge the effectiveness of exercise and other therapeutic treatments aimed at ameliorating the effects of muscle loss associated with aging.

Adult↗
PubMed2002

The mRNA expression of serotonin 2C subtype receptors uncoupled with inositol hydrolysis in NG108-15 cells.

Cell culture systems seem to be useful for clarifying the cellular physiological mechanisms of serotonin 2C subtype receptors (5-HT2CR) and related drug action mechanisms. However, there are still few reports about cells that contain intrinsic 5-HT2CR. This report demonstrates by using RT/PCR that 5-HT2CR mRNA exists in splicing variant forms in NGI08-15 cells. The PCR results using a pair of primers that recognized sequences near the third intracellular loop site showed two neighboring bands at about 500 bp upon electrophoresis in acrylamide gels. The sequence analysis demonstrated that one band was the rat 5-HT2CR sequence and the other one was that of the mouse. Serotonin, however, did not enhance the inositol phosphates formation in NG108-15 cells. It has been reported that post-translational modifications of RNA, splicing and editing, occur at the site of the second intracellular loop domain in 5-HT2CR mRNA. Accordingly, a pair of primers that recognized this site were designed. The molecular size of the PCR product was shorter than that expected based on the sequence of the native 5-HT2CR. The fragment lacked the 95 nucleotides of native 5-HT2CR mRNA. This seems to be the reason why serotonin did not enhance inositol phosphates formation in NG108-15 cells.

Animals↗
PubMed1997

Regulation of estrogen receptor alpha function in breast cancer.

Estrogen receptor alpha (ER) plays a key role in the development and progression of breast cancer as well as the treatment and outcome of breast cancer patients. In normal mammary epithelial cells, the level of ER fluctuates during the menstrual cycle in response to cyclical changes in estrogen. However, in breast cancer normal control of ER gene expression and/or function is lost. Of particular interest, the absence of ER in mammary carcinomas is associated with a less-differentiated phenotype and resistance to endocrine therapies. This review focuses on our current understanding of the mechanisms that regulate ER alpha gene expression and function in breast cancer. These include alteration of the ER gene, loss of gene expression, alternative splicing of ER RNA, posttranslational modification of the protein, and interaction of ER with other proteins that can modify its function.

Breast Neoplasms↗
PubMed1991

Development and use of monoclonal antibodies against an oncofetal protein associated with carcinogenesis and tumorigenesis.

An oncofetal protein (OFP) studied in our laboratory associated with embryogenesis, carcinogenesis and tumorigenesis has as its known biological function the modification of RNA release from isolated nuclei. In the present study, we have developed and investigated the use of monoclonal antibodies against OFP. Six hybridoma cell lines (A-F) were isolated by screening the hybridoma culture media for anti-OFP antibodies (MOFP) with an indirect ELISA and by testing the ability of these antibodies complexed with anti-mouse IgG-agarose to bind to rat OFP and remove its associated RNA transport activity from solution (Immunobioassay). An inhibition ELISA developed to measure OFP gave a linear response up to 20 ng of plasma protein from a tumor-bearing rat. Western blot analysis using these monoclonals showed that OFP from a rat tumor (H7777) cytosol that shed to the blood consisted of two species exhibiting molecular weights of 50 and 55 kD respectively. In order to show the usefulness of our assays, a preliminary study showing the ability of the immunobioassay to detect the expression of OFP in the plasma of carcinogen treated rats in a dosage dependent manner has been presented. Since OFP is produced in the target organ of rats shortly after treatment with carcinogens and persists in the preneoplastic foci and subsequent tumors, these monoclonal antibodies will be valuable in studying its involvement in chemical carcinogenesis and tumorigenesis.

Animals↗
PubMed1989

Effects of helio-neon laser radiation upon cellular cycle in a plant model.

The scope of this study was to investigate possible relationships between He-Neon laser radiation and mitotic and phase indices in meristematic cells of Allium cepa L. bulbs. Our results indicate that mitotic index increased after irradiation depending this modification on the time exposure and the potency of the He-Neon beam. Phase indices were also modified: frequency of prophase increased, while inter- meta- and anaphase decreased: telophases remain unchanged. These variations were significative only when the preparations were irradiated a) with 5 mW for 10 min. or more, b) with 10 mW or c) when the preparations were processed 60 min. after irradiation. These findings could not be attributed to thermal changes. Modifications in RNA or protein synthesis could be responsible.

Allium↗
PubMed1986

[Affinity modification of E. coli RNA-polymerase in a complex with the promoter by phosphorylating derivatives of primer oligonucleotides].

Oligonucleotides 2 to 7 nucleotide residues long, complementary to the codogenic strand of T7 promoter A2, have been synthesized; all of them contained a ribo-unit at the 3'-end. They were converted into 5'-(N-methyl)phosphoimidazolides, and the affinity reagents obtained were allowed to bind covalently to RNA polymerase in the presence of a promoter. Some of the nucleotide residues covalently attached occupied proper positions relative to the active centre of the phosphodiester bond synthesis and on addition of [alpha-32P]UTP were elongated, so that highly selective affinity labelling occurred. With oligonucleotides of various lengths, different distribution of the label between beta, beta' and sigma subunits of RNA polymerase took place. Most efficient was labelling of beta-subunit by the residue--pCpGpCpU, and of sigma-subunit by the residue--pApApApTp-CpGpCpU (p--radioactive phosphorus atom). In both cases, the amino acid residues labelled were histidines.

Binding Sites↗
PubMed1987

The mechanism of action of ricin and related toxic lectins on eukaryotic ribosomes. The site and the characteristics of the modification in 28 S ribosomal RNA caused by the toxins.

Ricin is a potent cytotoxic protein derived from the higher plant Ricinus communis that inactivates eukaryotic ribosomes. In this paper we have studied the mechanism of action of ricin A-chain on rat liver ribosomes in vitro. Our findings indicate that the toxin inactivates the ribosomes by modifying both or either of two nucleoside residues, G4323 and A4324, in 28 S rRNA. These nucleotides are located close to the alpha-sarcin cleavage site and become resistant to all ribonucleases tested. The examination of the lability of phosphodiester bonds of these nucleotides to both mild alkaline digestion and aniline treatment at acidic pH suggests that the base of A4324 is removed by the toxin. This unique activity of ricin A-chain was also observed when naked 28 S rRNA is used as a substrate, indicating that the toxin directly acts on the RNA. Similar activity on 28 S rRNA is also exhibited by abrin and modeccin, ricin-related toxins, suggesting a general mechanistic pathway for ribosome inactivation by lectin toxins.

Animals↗
PubMed1986

[Effect of sodium selenite on tumor cells in culture].

Morphofunctional changes in HeLa cell culture following treatment with various concentrations of selenium ion during 2, 4 and 24 hours are described. Variations in mitotic index, duration of separate mitotic stages and a profile of pathologic mitoses were established. Inhibition of cell entry into the S-phase of mitotic cycle and modifications of RNA and protein synthesis after treatment with 0.1 and 0.25 ppm of the trace element was shown autoradiographically. Increased destruction of cell monolayer following contact with selenium was demonstrated by light, scanning and transmission electron microscopy. It is suggested that selenium exerts a toxic effect on tumor cells although this mechanism is not yet clear.

HeLa Cells↗
PubMed1983

Tertiary structure of the eukaryotic ribosomal 5 S RNA. Accessibility of phosphodiester bonds to ethylnitrosourea modification.

The tertiary structure of the eukaryotic ribosomal 5 S RNA was examined using ethylnitrosourea reactivity as a probe for phosphodiester bonds. In three different 5 S RNAs of diverse origin the reactivity was restricted to the same three regions of the sequence, corresponding to residues G 99-A 101, A 88-G 89, and G 75 in the rat 5 S RNA molecule. All of these restricted residues are in highly conserved sequences; five of the residues (G 75, G 89, G 99, A 100, and A 101 in the rat) are present in all 5 S RNAs. The results indicate that, as has been suggested for the secondary structure, the tertiary structure of the 5 S RNA is also highly conserved. Based on these data, a working model for the tertiary structure is suggested which is consistent with previous studies on the structure of the free RNA and 5 S RNA-protein complexes.

Animals↗
PubMed1982

The nucleotide sequence of tRNA4Val of Drosophila melanogaster. Chloroacetaldehyde modification as an aid to RNA sequencing.

The nucleotide sequence of tRNA4Val from Drosophila melanogaster was determined to be pGUUUmCCGUm1GGUG psi AGCGGDU(acp3U)AUCACA psi CUGCCmUIACAm5CGCAGAAGm7GCCCCCGGT psi CGm1AUCCCGGGCGGAAACACCA. It is probable that residue C 49 is modified to m5C. The use of tRNA modified with chloroacetaldehyde to overcome secondary structure problems in sequencing is described.

Acetaldehyde↗