scholarly journals Signal Transduction Protein PII Is Required for NtcA-Regulated Gene Expression during Nitrogen Deprivation in the Cyanobacterium Synechococcus elongatus Strain PCC 7942

2003 ◽  
Vol 185 (8) ◽  
pp. 2582-2591 ◽  
Author(s):  
M. Fadi Aldehni ◽  
Jörg Sauer ◽  
Christian Spielhaupter ◽  
Roland Schmid ◽  
Karl Forchhammer
Keyword(s):  
Gene Expression ◽  
Signal Transduction ◽  
Synechococcus Elongatus ◽  
Dependent Manner ◽  
Nitrogen Deprivation ◽  
Wild Type ◽  
Combined Nitrogen ◽  
Signal Transduction Protein ◽  
Regulated Gene Expression ◽  
Pcc 7942

ABSTRACT The transcription factor of the cyclic AMP receptor protein/FNR family, NtcA, and the PII signaling protein play central roles in global nitrogen control in cyanobacteria. A dependence on PII for NtcA-regulated transcription, however, has not been observed. In the present investigation, we examined alterations in gene expression following nitrogen deprivation in Synechococcus elongatus strain PCC 7942 and specifically the roles of NtcA and PII. Global changes in de novo protein synthesis following combined-nitrogen deprivation were visualized by in vivo [35S]methionine labeling and two-dimensional polyacrylamide gel electrophoresis analysis. Nearly all proteins whose synthesis responded specifically to combined-nitrogen deprivation in wild-type cells of S. elongatus failed to respond in PII- and NtcA-deficient mutants. One of the proteins whose synthesis was down-regulated in a PII- and NtcA-dependent manner was RbcS, the small subunit of RubisCO. Quantification of its mRNA revealed that the abundance of the rbcLS transcript following combined-nitrogen deprivation rapidly declined in wild-type cells but not in PII and NtcA mutant cells. To investigate further the relationship between PII and NtcA, fusions of the promotorless luxAB reporter genes to the NtcA-regulated glnB gene were constructed and these constructs were used to transform wild-type cells and PII − and NtcA− mutants. Determination of bioluminescence under different growth conditions showed that NtcA represses gene expression in the presence of ammonium in a PII-independent manner. By contrast, NtcA-dependent activation of glnB expression following combined-nitrogen deprivation was impaired in the absence of PII. Together, these results suggest that under conditions of combined-nitrogen deprivation, the regulation of NtcA-dependent gene expression requires the PII signal transduction protein.

scholarly journals The NtcA-Regulated amtB Gene Is Necessary for Full Methylammonium Uptake Activity in the Cyanobacterium Synechococcus elongatus

2007 ◽  
Vol 189 (21) ◽  
pp. 7791-7798 ◽  
Author(s):  
Javier Paz-Yepes ◽  
Antonia Herrero ◽  
Enrique Flores
Keyword(s):  
Synechococcus Elongatus ◽  
Nitrogen Deprivation ◽  
Wild Type ◽  
Noticeable Effect ◽  
Unicellular Cyanobacterium ◽  
Net Uptake ◽  
In The Wild ◽  
Uptake Activity ◽  
Step Down ◽  
Pcc 7942

ABSTRACT The Amt proteins constitute a ubiquitous family of transmembrane ammonia channels that permit the net uptake of ammonium by cells. In many organisms, there is more than one amt gene, and these genes are subjected to nitrogen control. The mature Amt protein is a homo- or heterooligomer of three Amt subunits. We previously characterized an amt1 gene in the unicellular cyanobacterium Synechococcus elongatus strain PCC 7942. In this work, we describe the presence in this organism of a second amt gene, amtB, which encodes a protein more similar to the bacterial AmtB proteins than to any other characterized cyanobacterial Amt protein. The expression of amtB took place in response to nitrogen step-down, required the NtcA transcription factor, and occurred parallel to the expression of amt1. However, the transcript levels of amtB measured after 2 h of nitrogen deprivation were about 100-fold lower than those of amt1. An S. elongatus amtB insertional mutant exhibited an activity for uptake of [14C]methylammonium that was about 55% of that observed in the wild type, but inactivation of amtB had no noticeable effect on the uptake of ammonium when it was supplied at a concentration of 100 μM or more. Because an S. elongatus amt1 mutant is essentially devoid of [14C]methylammonium uptake activity, the mature Amt transporter is functional in the absence of AmtB subunits but not in the absence of Amt1 subunits. However, the S. elongatus amtB mutant could not concentrate [14C]methylammonium within the cells to the same extent as the wild type. Therefore, AmtB is necessary for full methylammonium uptake activity in S. elongatus.

scholarly journals Interactions between the Nitrogen Signal Transduction Protein PII and N-Acetyl Glutamate Kinase in Organisms That Perform Oxygenic Photosynthesis

2004 ◽  
Vol 186 (11) ◽  
pp. 3346-3354 ◽  
Author(s):  
Sergio Burillo ◽  
Ignacio Luque ◽  
Inmaculada Fuentes ◽  
Asunción Contreras
Keyword(s):  
Signal Transduction ◽  
Oxygenic Photosynthesis ◽  
Yeast Two Hybrid ◽  
Hybrid Approaches ◽  
Signal Transduction Protein ◽  
Photosynthetic Eukaryotes ◽  
Key Enzyme ◽  
Signal Transduction Proteins ◽  
Pcc 7942 ◽  
Two Hybrid

ABSTRACT PII, one of the most conserved signal transduction proteins, is believed to be a key player in the coordination of nitrogen assimilation and carbon metabolism in bacteria, archaea, and plants. However, the identity of PII receptors remains elusive, particularly in photosynthetic organisms. Here we used yeast two-hybrid approaches to identify new PII receptors and to explore the extent of conservation of PII signaling mechanisms between eubacteria and photosynthetic eukaryotes. Screening of Synechococcus sp. strain PCC 7942 libraries with PII as bait resulted in identification of N-acetyl glutamate kinase (NAGK), a key enzyme in the biosynthesis of arginine. The integrity of Ser49, a residue conserved in PII proteins from organisms that perform oxygenic photosynthesis, appears to be essential for NAGK binding. The effect of glnB mutations on NAGK activity is consistent with positive regulation of NAGK by PII. Phylogenetic and yeast two-hybrid analyses strongly suggest that there was conservation of the NAGK-PII regulatory interaction in the evolution of cyanobacteria and chloroplasts, providing insight into the function of eukaryotic PII-like proteins.

scholarly journals Two classes of mutant mammary tumor virus-infected HTC cell with defects in glucocorticoid-regulated gene expression.

1983 ◽  
Vol 3 (2) ◽  
pp. 149-160 ◽  
Author(s):  
G L Firestone ◽  
K R Yamamoto
Keyword(s):  
Gene Expression ◽  
Cell Surface ◽  
Mammary Tumor ◽  
Hormonal Regulation ◽  
Wild Type ◽  
Viral Glycoprotein ◽  
Mammary Tumor Virus ◽  
Viral Glycoproteins ◽  
Tumor Virus ◽  
Regulated Gene Expression

We have isolated mutant derivatives of M1.54 (a mammary tumor virus [MTV]-infected rat hepatoma [HTC] cell line containing multiple integrated proviruses) that fail to express hormone-inducible cell surface viral glycoproteins. In wild-type M1.54, the synthetic glucocorticoid dexamethasone selectively stimulates the rate of synthesis of MTV RNA. In addition, dexamethasone is essential for posttranslational maturation of three of the four cell surface viral glycoproteins processed from the MTV glycosylated precursor polyprotein; the fourth mature species is produced constitutively. Two mutant phenotypes are described; each contains glucocorticoid receptors that are indistinguishable from the wild-type receptor with respect to hormone affinity, intracellular concentration, nuclear translocation efficiency, DNA-cellulose chromatography, and sedimentation rate. In one class, represented by the mutant line CR1, dexamethasone fails to stimulate the low basal rate of MTV gene transcription; surprisingly, hormonal regulation of tyrosine aminotransferase activity is also defective in CR1, whereas several other cellular responses to dexamethasone are normal. In the second class of mutants, represented by CR4, dexamethasone stimulates synthesis of MTV transcripts indistinguishable from those produced in M1.54, but only the constitutive cell surface viral glycoprotein is expressed. Thus, these mutants define two distinct and novel aspects of glucocorticoid regulated gene expression in HTC cells: CR4 contains a defect in a hormone inducible protein maturation pathway that acts on specific viral (and presumably cellular) precursor polypeptides, whereas the lesion in CR1 appears to affect the expression of a subset of the gene products normally under glucocorticoid control in M1.54.

Human glucagon gene promoter sequences regulating tissue-specific versus nutrient-regulated gene expression

2002 ◽  
Vol 282 (1) ◽  
pp. R173-R183 ◽  
Author(s):  
Min Nian ◽  
Jun Gu ◽  
David M. Irwin ◽  
Daniel J. Drucker
Keyword(s):  
Gene Expression ◽  
Gene Promoter ◽  
Regulatory Sequences ◽  
Dependent Manner ◽  
Specific Expression ◽  
Tissue Specific ◽  
High Fiber ◽  
Fiber Diet ◽  
Regulated Gene Expression

The glucagon-like peptides (GLPs) are synthesized and secreted in a nutrient-dependent manner in rodents; however, the factors regulating human GLP-1 and GLP-2 biosynthesis remain unclear. To understand how nutrients regulate human proglucagon gene expression, we studied the expression of a human proglucagon promoter-growth hormone (GH) transgene in 1.6 human glucagon-GH transgenic mice. Fasting-refeeding significantly decreased and increased the levels of circulating mouse insulin and transgene-derived hGH ( P < 0.05 fasting vs. refeeding) and decreased and upregulated, respectively, the levels of endogenous mouse proglucagon RNA in the ileum but not in the jejunum or colon. High-fiber feeding significantly increased the levels of glucose-stimulated circulating hGH and upregulated levels of mouse intestinal proglucagon gene expression in the jejunum, ileum, and colon ( P < 0.05, 0 vs. 30% fiber diet). In contrast, neither fasting-refeeding nor a high-fiber diet upregulated the expression of the human proglucagon promoter-hGH transgene. These findings demonstrate that human proglucagon gene regulatory sequences specifying tissue-specific expression in gut endocrine cells are not sufficient for recognition of energy-derived signals regulating murine glucagon gene expression in enteroendocrine cells in vivo.

scholarly journals The TEA Transcription Factor Tec1 Confers Promoter-Specific Gene Regulation by Ste12-Dependent and -Independent Mechanisms

2010 ◽  
Vol 9 (4) ◽  
pp. 514-531 ◽  
Author(s):  
Barbara Heise ◽  
Julia van der Felden ◽  
Sandra Kern ◽  
Mario Malcher ◽  
Stefan Brückner ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Transcriptional Activation ◽  
Binding Sites ◽  
Target Genes ◽  
Specific Gene ◽  
Dependent Manner ◽  
A Genome ◽  
Regulated Gene Expression

ABSTRACT In Saccharomyces cerevisiae, the TEA transcription factor Tec1 is known to regulate target genes together with a second transcription factor, Ste12. Tec1-Ste12 complexes can activate transcription through Tec1 binding sites (TCSs), which can be further combined with Ste12 binding sites (PREs) for cooperative DNA binding. However, previous studies have hinted that Tec1 might regulate transcription also without Ste12. Here, we show that in vivo, physiological amounts of Tec1 are sufficient to stimulate TCS-mediated gene expression and transcription of the FLO11 gene in the absence of Ste12. In vitro, Tec1 is able to bind TCS elements with high affinity and specificity without Ste12. Furthermore, Tec1 contains a C-terminal transcriptional activation domain that confers Ste12-independent activation of TCS-regulated gene expression. On a genome-wide scale, we identified 302 Tec1 target genes that constitute two distinct classes. A first class of 254 genes is regulated by Tec1 in a Ste12-dependent manner and is enriched for genes that are bound by Tec1 and Ste12 in vivo. In contrast, a second class of 48 genes can be regulated by Tec1 independently of Ste12 and is enriched for genes that are bound by the stress transcription factors Yap6, Nrg1, Cin5, Skn7, Hsf1, and Msn4. Finally, we find that combinatorial control by Tec1-Ste12 complexes stabilizes Tec1 against degradation. Our study suggests that Tec1 is able to regulate TCS-mediated gene expression by Ste12-dependent and Ste12-independent mechanisms that enable promoter-specific transcriptional control.

Phytochrome signal-transduction: characterization of pathways and isolation of mutants

1995 ◽  
Vol 350 (1331) ◽  
pp. 67-74 ◽  
Keyword(s):  
Gene Expression ◽  
Signal Transduction ◽  
Red Light ◽  
Signal Transduction Pathway ◽  
Regulatory Elements ◽  
Signal Transduction Pathways ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
Regulated Gene Expression ◽  
Dependent Pathway

The study of phytochrome signalling has yielded a wealth of data describing both the perception of light by the receptor, and the terminal steps in phytochrome-regulated gene expression by a number of transcription factors. We are now focusing on establishing the intervening steps linking phytochrome photoactivation to gene expression, and the regulation and interactions of these signalling pathways. Recent work has utilized both a pharmacological approach in phototrophic soybean suspension cultures and microinjection techniques in tomato to establish three distinct phytochrome signal-transduction pathways: (i) a calcium-dependent pathway that regulates the expression of genes encoding the chlorophyll a/b binding protein ( CAB ) and other components of photosystem II; (ii) a cGMP-dependent pathway that regulates the expression of the gene encoding chalcone synthase ( CHS ) and the production of anthocyanin pigments; and (iii) a pathway dependent upon both calcium and cGMP that regulates the expression of genes encoding components of photosystem I and is necessary for the production of mature chloroplasts. To study the components and the regulation of phytochrome signal-transduction pathways, mutants with altered photomorphogenic responses have been isolated by a number of laboratories. However, with several possible exceptions, little real progress has been made towards the isolation of mutants in positive regulatory elements of the phytochrome signal-transduction pathway. We have characterized a novel phytochrome A (phyA)-mediated far-red light (FR) response in Arabidopsis seedlings which we are currently using to screen for specific phyA signal-transduction mutants.

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