scholarly journals Role of an RNase III Binding Site in Transcription Termination at λ nutL by HK022 Nun Protein

2006 ◽  
Vol 188 (19) ◽  
pp. 6824-6831 ◽  
Author(s):  
Robert S. Washburn ◽  
Donald L. Court ◽  
Max E. Gottesman
Keyword(s):  
Binding Site ◽  
Transcription Termination ◽  
Rnase Iii ◽  
Specific Element ◽  
Rate Limiting

ABSTRACT The phage HK022 Nun protein excludes phage λ by binding nascent λ p L and p R transcripts at nutL and nutR, respectively, and inducing transcription termination just downstream of these sites. Termination is more efficient at nutL than at nutR. One difference between nutL and nutR is the presence of RNase III processing sites (rIII) located immediately promoter distal to λ nutL. We found that deletion of rIII dramatically reduced Nun transcription arrest in vitro but had little effect on termination in vivo. However, consistent with the in vitro results, overexpression of a transcript carrying nutL and rIII efficiently titrated Nun, allowing λ to grow on a strain that expressed Nun, whereas a transcript carrying only nutL or nutL-rIII with nucleotides 97 to 141 deleted was ineffective. Rnc70, an RNase III mutant that binds but does not cleave rIII, also prevented Nun-mediated λ exclusion. We propose that rIII enhances the on-rate of Nun at nutL, stimulating Nun-mediated arrest in vitro. We have shown that a specific element in rIII, i.e., box C (G89GUGUGUG), strongly enhances arrest on rIII + templates. Nun-rIII interactions do not stimulate Nun termination in vivo, presumably because formation of the Nun-nutL complex is normally not rate-limiting in the cell. In contrast to Nun, N is not occluded by Rnc70 and is not efficiently titrated by a nutL-rIII transcript.

scholarly journals In Vivo Effect of Mutations at the PRPP Binding Site of the Bacillus subtilis Purine Repressor

2003 ◽  
Vol 185 (22) ◽  
pp. 6728-6731 ◽  
Author(s):  
Pekka Rappu ◽  
Terhi Pullinen ◽  
Pekka Mäntsälä
Keyword(s):  
Bacillus Subtilis ◽  
Binding Site ◽  
Binding Motif

ABSTRACT The Bacillus subtilis PurR mediates adenine repression and guanosine induction of purA. PRPP inhibits binding of PurR to DNA in vitro. Mutations in the PRPP binding motif of PurR caused strong repression regardless of purine exclusions or additions, establishing the role of PRPP as regulator of PurR.

scholarly journals Transcription Termination and 3′-End Processing of the Spliced Leader RNA in Kinetoplastids

1999 ◽  
Vol 19 (2) ◽  
pp. 1595-1604 ◽  
Author(s):  
Nancy R. Sturm ◽  
Michael C. Yu ◽  
David A. Campbell
Keyword(s):  
Binding Site ◽  
Transcription Termination ◽  
Small Nuclear Rna ◽  
Stem Loop ◽  
Spliced Leader ◽  
Nuclear Extracts ◽  
Sequence Elements ◽  
Rna Genes

ABSTRACT Addition of a 39-nucleotide (nt) spliced leader (SL) bytrans splicing is a basic requirement for all trypanosome nuclear mRNAs. The SL RNA in Leishmania tarentolae is a 96-nt precursor transcript synthesized by a polymerase that resembles polymerase II most closely. To analyze SL RNA genesis, we mutated SL RNA intron structures and sequence elements: stem-loops II and III, the Sm-binding site, and the downstream T tract. Using an exon-tagged SL RNA gene, we examined the phenotypes produced by a second-site 10-bp linker scan mutagenic series and directed mutagenesis. Here we report that transcription is terminated by the T tract, which is common to the 3′ end of all kinetoplastid SL RNA genes, and that more than six T’s are required for efficient termination in vivo. We describe mutants whose SL RNAs end in the T tract or appear to lack efficient termination but can generate wild-type 3′ ends. Transcriptionally active nuclear extracts show staggered products in the T tract, directed by eight or more T’s. The in vivo and in vitro data suggest that SL RNA transcription termination is staggered in the T tract and is followed by nucleolytic processing to generate the mature 3′ end. We show that the Sm-binding site and stem-loop III structures are necessary for correct 3′-end formation. Thus, we have defined the transcription termination element for the SL RNA gene. The termination mechanism differs from that of vertebrate small nuclear RNA genes and the SL RNA homologue in Ascaris.

scholarly journals GCUNC-45 Is a Novel Regulator for the Progesterone Receptor/hsp90 Chaperoning Pathway

2006 ◽  
Vol 26 (5) ◽  
pp. 1722-1730 ◽  
Author(s):  
Ahmed Chadli ◽  
J. Dinny Graham ◽  
M. Greg Abel ◽  
Twila A. Jackson ◽  
David F. Gordon ◽  
...  
Keyword(s):  
Progesterone Receptor ◽  
Atpase Activity ◽  
Binding Site ◽  
Signaling Pathway ◽  
Regulatory Proteins ◽  
N Terminus ◽  
Positive Factor

ABSTRACT The hsp90 chaperoning pathway is a multiprotein system that is required for the production or activation of many cell regulatory proteins, including the progesterone receptor (PR). We report here the identity of GCUNC-45 as a novel modulator of PR chaperoning by hsp90. GCUNC-45, previously implicated in the activities of myosins, can interact in vivo and in vitro with both PR-A and PR-B and with hsp90. Overexpression and knockdown experiments show GCUNC-45 to be a positive factor in promoting PR function in the cell. GCUNC-45 binds to the ATP-binding domain of hsp90 to prevent the activation of its ATPase activity by the cochaperone Aha1. This effect limits PR chaperoning by hsp90, but this can be reversed by FKBP52, a cochaperone that is thought to act later in the pathway. These findings reveal a new cochaperone binding site near the N terminus of hsp90, add insight on the role of FKBP52, and identify GCUNC-45 as a novel regulator of the PR signaling pathway.

scholarly journals FoxO1 Is a Novel Regulator of 20S Proteasome Subunits Expression and Activity

2021 ◽  
Vol 9 ◽  
Author(s):  
Marianna Kapetanou ◽  
Tobias Nespital ◽  
Luke S. Tain ◽  
Andre Pahl ◽  
Linda Partridge ◽  
...  
Keyword(s):  
Proteasome Activity ◽  
20S Proteasome ◽  
Direct Role ◽  
Forkhead Box ◽  
Age Related ◽  
Proteasome Subunits ◽  
Rate Limiting

Proteostasis collapses during aging resulting, among other things, in the accumulation of damaged and aggregated proteins. The proteasome is the main cellular proteolytic system and plays a fundamental role in the maintenance of protein homeostasis. Our previous work has demonstrated that senescence and aging are related to a decline in proteasome content and activities, while its activation extends lifespan in vitro and in vivo in various species. However, the mechanisms underlying this age-related decline of proteasome function and the down-regulation in expression of its subunits remain largely unclear. Here, we demonstrate that the Forkhead box-O1 (FoxO1) transcription factor directly regulates the expression of a 20S proteasome catalytic subunit and, hence, proteasome activity. Specifically, we demonstrate that knockout of FoxO1, but not of FoxO3, in mice severely impairs proteasome activity in several tissues, while depletion of IRS1 enhances proteasome function. Importantly, we show that FoxO1 directly binds on the promoter region of the rate-limiting catalytic β5 proteasome subunit to regulate its expression. In summary, this study reveals the direct role of FoxO factors in the regulation of proteasome function and provides new insight into how FoxOs affect proteostasis and, in turn, longevity.

scholarly journals Genome-Wide Prediction and Analysis of Yeast RNase III-Dependent snoRNA Processing Signals

2005 ◽  
Vol 25 (8) ◽  
pp. 2981-2994 ◽  
Author(s):  
Ghada Ghazal ◽  
Dongling Ge ◽  
Julien Gervais-Bird ◽  
Jules Gagnon ◽  
Sherif Abou Elela
Keyword(s):  
Rrna Synthesis ◽  
Ribosomal Protein Genes ◽  
Rnase Iii ◽  
Double Stranded Rna ◽  
In Vivo Experiments ◽  
Genome Wide ◽  
Nucleolar Rnas

ABSTRACT In Saccharomyces cerevisiae, the maturation of both pre-rRNA and pre-small nucleolar RNAs (pre-snoRNAs) involves common factors, thereby providing a potential mechanism for the coregulation of snoRNA and rRNA synthesis. In this study, we examined the global impact of the double-stranded-RNA-specific RNase Rnt1p, which is required for pre-rRNA processing, on the maturation of all known snoRNAs. In silico searches for Rnt1p cleavage signals, and genome-wide analysis of the Rnt1p-dependent expression profile, identified seven new Rnt1p substrates. Interestingly, two of the newly identified Rnt1p-dependent snoRNAs, snR39 and snR59, are located in the introns of the ribosomal protein genes RPL7A and RPL7B. In vitro and in vivo experiments indicated that snR39 is normally processed from the lariat of RPL7A, suggesting that the expressions of RPL7A and snR39 are linked. In contrast, snR59 is produced by a direct cleavage of the RPL7B pre-mRNA, indicating that a single pre-mRNA transcript cannot be spliced to produce a mature RPL7B mRNA and processed by Rnt1p to produce a mature snR59 simultaneously. The results presented here reveal a new role of yeast RNase III in the processing of intron-encoded snoRNAs that permits independent regulation of the host mRNA and its associated snoRNA.

Effects of acid-base changes and carbonic anhydrase inhibition on pancreatic secretion

1963 ◽  
Vol 205 (4) ◽  
pp. 651-657 ◽  
Author(s):  
James A. Rawls ◽  
Per J. Wistrand ◽  
Thomas H. Maren
Keyword(s):  
Carbonic Anhydrase ◽  
Acid Base ◽  
Metabolic Alterations ◽  
Uncatalyzed Reaction ◽  
Output Increase ◽  
Rate Limiting ◽  
In Vitro Kinetics

Pancreatic flow and HCO3– and Cl– output were studied in dogs following 2 U/kg (i.v.) of secretin. Acetazolamide reduced flow and HCO3– output to half normal. HCl produced the same effect. NaHCO3 increased flow and HCO3– output. CO2 produced little change. Severe hyperventilation decreased flow and HCO3– output. Results are consistent with secretion dependent on the over-all reaction OH– + CO2 → HCO3–, with both a carbonic-anhydrase catalyzed and an uncatalyzed component. Reduction of either reactant or of enzyme decreased output: increase of the reactants increased output. From in vitro kinetics and analysis of rates in vivo, the role of carbonic anhydrase may be assessed. About half of HCO3– output normally depends on the uncatalyzed reaction, and half on the catalyzed. In metabolic alterations, only the uncatalyzed component is affected. Pancreatic carbonic anhydrase is greatly in excess of that needed for the observed catalyzed rate in vivo. Correspondingly, reduction of output by acetazolamide occurs only when >99% of pancreatic carbonic anhydrase is inhibited. It is suggested that the rate-limiting event in pancreatic HCO3– secretion is transport of HCO3– from cell to duct.

Role of albumin's copper binding site in copper uptake by mouse hepatocytes

1990 ◽  
Vol 258 (6) ◽  
pp. G988-G991 ◽  
Author(s):  
H. J. McArdle ◽  
S. M. Gross ◽  
D. M. Danks ◽  
A. G. Wedd
Keyword(s):  
Binding Site ◽  
Ternary Complex ◽  
Specific Binding ◽  
Specific Site ◽  
Copper Binding ◽  
Copper Uptake ◽  
Mouse Hepatocytes

It is possible, in vitro, to label albumin with copper either exclusively on the specific binding site or partly on the specific site and also on other sites by altering the pH at which the two ligands are mixed. Copper attached exclusively to the specific site is taken up more rapidly than copper attached to that site and others on albumin. The effect is proportional to the amount of copper on the specific site. Additional histidine stimulates uptake irrespective of the copper binding site on albumin. The effect is related to the histidine on position 3 of the albumin, since it is not seen when dog albumin is labeled under the same conditions. The data suggest that the cell recognizes and presumably binds the copper-albumin (CuAlb) complex but may preferentially recognize the ternary complex formed by CuAlb and histidine. We suggest that, in vivo, copper is bound mainly as the ternary complex and that the structure formed, presumably similar to that formed by a copper-histidine complex, is what is actually recognized by the cell. After binding, the albumin and histidine are released, possibly by a reduction step, and the copper is transported across the membrane. If the copper cannot be transported (as occurs when the cells are incubated at 4 degrees C), it blocks further binding of the ternary complex.

The Physiologic Activity and Mechanism of Quercetin-Like Natural Plant Flavonoids

2020 ◽  
Vol 21 (8) ◽  
pp. 654-658 ◽  
Author(s):  
Wujun Chen ◽  
Shuai Wang ◽  
Yudong Wu ◽  
Xin Shen ◽  
Shutan Xu ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Normal Diet ◽  
The Body ◽  
Natural Plant ◽  
Physiological Functions ◽  
Physiologic Activity ◽  
Rate Limiting

The term “vitamin P” is an old but interesting concept. Most substances in this category belong to the family of flavonoids. “Vitamin P” has also been used to define the activity of some flavonoids, including quercetin, myricetin, and rutin. According to experimental studies, the “quercetin-like natural plant flavonoids” are beneficial to the body due to their various physiological and pharmacological activities in large doses (5 μM in vitro, 50 mg/kg in mice and 100 mg/kg in rats). The physiologically achievable concentration is 10 to 100 nM, which is quite high and hard to achieve from a normal diet. Thus, the physiologic activity and mechanism of "vitamin P" are still not clear. It should be noted that the quercetin-like natural plant flavonoids are physiological co-factors of cyclooxygenases (COXs), which are the rate-limiting key enzymes of prostaglandins. These quercetin-like natural plant flavonoids can strongly stimulate prostaglandin levels at lower doses (10 nM in vitro and in 0.1 mg/kg in vivo in rats). Although these "vitamin P" substances are not original substances in the body, their physiological functions affect the body. This review is focused on the most compelling evidence regarding the physiologic role and mechanism of quercetin-like natural plant flavonoids, which may be useful in understanding the physiological functions of "vitamin P", with the goal of focusing on the role of flavonoids in human physiological health.

The Role of Polyphenols in the Modulation of Plasma Non-Enzymatic Antioxidant Capacity (NEAC)

2012 ◽  
Vol 82 (3) ◽  
pp. 228-232 ◽  
Author(s):  
Mauro Serafini ◽  
Giuseppa Morabito
Keyword(s):  
Antioxidant Capacity ◽  
Dietary Intervention ◽  
Ex Vivo ◽  
The Body ◽  
Dietary Polyphenols ◽  
Enzymatic Antioxidant ◽  
Endogenous Antioxidant

Dietary polyphenols have been shown to scavenge free radicals, modulating cellular redox transcription factors in different in vitro and ex vivo models. Dietary intervention studies have shown that consumption of plant foods modulates plasma Non-Enzymatic Antioxidant Capacity (NEAC), a biomarker of the endogenous antioxidant network, in human subjects. However, the identification of the molecules responsible for this effect are yet to be obtained and evidences of an antioxidant in vivo action of polyphenols are conflicting. There is a clear discrepancy between polyphenols (PP) concentration in body fluids and the extent of increase of plasma NEAC. The low degree of absorption and the extensive metabolism of PP within the body have raised questions about their contribution to the endogenous antioxidant network. This work will discuss the role of polyphenols from galenic preparation, food extracts, and selected dietary sources as modulators of plasma NEAC in humans.

Anti-obesity role of Aster glehni extract: in vivo and in vitro effects

Planta Medica ◽  
2012 ◽  
Vol 78 (11) ◽  
Author(s):  
HM Lee ◽  
TG Ahn ◽  
CW Kim ◽  
HJ An
Keyword(s):  
In Vitro Effects
Sign in / Sign up

Export Citation Format

Share Document