Showing papers on "Psychological repression published in 1990"
TL;DR: Findings reveal a cross talk between two major signal transduction systems used to control gene transcription in response to extracellular stimuli, and a novel mechanism for transcriptional repression.
1,531 citations
TL;DR: It is shown that the transcriptional activity of seven maize photosynthetic gene promoters is specifically and coordinately repressed by the photosynthesis end products sucrose and glucose and by the exogenous carbon source acetate.
Abstract: Using freshly isolated maize mesophyll protoplasts and a transient expression method, I showed that the transcriptional activity of seven maize photosynthetic gene promoters is specifically and coordinately repressed by the photosynthetic end products sucrose and glucose and by the exogenous carbon source acetate. Analysis of deleted, mutated, and hybrid promoters showed that sugars and acetate inhibit the activity of distinct positive upstream regulatory elements without a common consensus. The metabolic repression of photosynthetic genes overrides other forms of regulation, e.g., light, tissue type, and developmental stage. Repression by sugars and repression by acetate are mediated by different mechanisms. The identification of conditions that avoid sugar repression overcomes a major obstacle to the study of photosynthetic gene regulation in higher plants.
714 citations
TL;DR: Under conditions where loop formation is impossible, occupation of O3 but not of O2 may lead to weak repression, which suggests that under these conditions CAP activation may be inhibited and that stopping transcription at O2 does not significantly contribute to repression.
Abstract: We tested the effect of systematic destruction of all three lac operators of the chromosomal lac operon of Escherichia coli on repression by Lac repressor. Absence of just one 'pseudo-operator' O2 or O3 decreases repression by wild-type tetrameric Lac repressor approximately 2- to 3-fold; absence of both 'pseudo-operators' decreases repression greater than 50-fold. O1 alone represses under these conditions only approximately 20-fold. Dimeric active Lac repressor (iadi) represses the wild-type lac operon to about the same low extent. This indicates that cooperative interaction between lac operators is due to DNA loop formation mediated by tetrameric Lac repressor. Under conditions where loop formation is impossible, occupation of O3 but not of O2 may lead to weak repression. This suggests that under these conditions CAP activation may be inhibited and that stopping transcription at O2 does not significantly contribute to repression.
490 citations
TL;DR: The results suggest that senescent fibroblasts were unable to proliferate because of, at least in part, selective repression of c-fos; moreover, the multiple changes in gene expression support the view that cellular senescence is a process of terminal differentiation.
Abstract: Normal cells in culture invariably undergo senescence, whereby they cease proliferation after a finite number of doublings. Irreversible changes in gene expression occurred in senescent human fetal lung fibroblasts: a non-cell cycle-regulated mRNA was partially repressed; an unusual polyadenylated histone mRNA was expressed; although serum induced c-H-ras, c-myc, and ornithine decarboxylase mRNA normally, ornithine decarboxylase activity was deficient; and serum did not induce mRNA for a replication-dependent histone and for the c-fos proto-oncogene. The loss of c-fos inducibility was the result of a specific, transcriptional block. The results suggest that senescent fibroblasts were unable to proliferate because of, at least in part, selective repression of c-fos; moreover, the multiple changes in gene expression support the view that cellular senescence is a process of terminal differentiation.
472 citations
TL;DR: It is shown here that four positions of histone H4 (N-terminal residues 16, 17, 18, and 19) are crucial to silencing and provides a link between one of the SIR proteins and a component of chromatin.
Abstract: Repression of transcription from the silent mating loci (HML alpha and HMRa) is essential for mating ability in Saccharomyces cerevisiae. This silencing is known to require at least five proteins (SIR1, SIR2, SIR3, SIR4, and histone H4) and is accompanied by a change in chromatin structure. We show here that four positions of histone H4 (N-terminal residues 16, 17, 18, and 19) are crucial to silencing. HML alpha and HMRa are efficiently repressed when these positions are occupied by basic amino acids but are derepressed when substituted with glycine. These results suggest that acetylation of Lys-16 would lead to derepression of the silent mating loci. Three strong extragenic suppressors of the latter H4 mutations were isolated and determined to be located in SIR3. These suppressors allow high mating efficiencies in cells expressing either wild-type H4 or H4 containing single amino acid substitutions. They did not allow efficient mating in a strain that contained an H4 N-terminal deletion. These results indicate that the SIR3 mutations do not bypass the requirement for the H4 N terminus but, rather, allow repression in the presence of a less than optimal H4 N terminus. This provides a link between one of the SIR proteins and a component of chromatin.
334 citations
TL;DR: Although many mutations reduced the repression ratio 3- to 11-fold, some also caused a 2-fold or greater increase in amylase production and some caused hyperproduction without affecting catabolite repression.
Abstract: Catabolite repression of the Bacillus subtilis alpha-amylase gene (amyE) involves an operator sequence located just downstream of the promoter (amyR), overlapping the transcription start site. Oligonucleotide site-directed mutagenesis of this sequence identified bases required for catabolite repression. Two mutations increased both the 2-fold symmetry of the operator and the repression ratio. Although many mutations reduced the repression ratio 3- to 11-fold, some also caused a 2-fold or greater increase in amylase production. Others caused hyperproduction without affecting catabolite repression. Homologous sequences in other catabolite-repressed B. subtilis promoters suggest a common regulatory site may be involved in catabolite repression.
311 citations
TL;DR: E2-mediated repression of HPV-18 P105 promoter activity was shown to be a transcriptional effect and the interaction of E2 with promoter-proximal E2-binding sites is likely to be important for the controlled expression of viral genes transcribed from the HPV-16 P97 promoter and the HPV in infected human genital epithelial cells.
Abstract: cis-Acting elements involved in E2 modulation of human papillomavirus type 16 (HPV-16) P97 promoter activity and HPV-18 P105 promoter activity were examined. In transfected primary human keratinocytes, each promoter had a basal activity that could be repressed by the bovine papillomavirus type 1 E2 gene product. Mutational analysis of the E2-binding sites in the long control region upstream of each promoter revealed that E2 repression was mediated through the E2-binding sites proximal to each promoter. In the context of a mutated E2-binding site at the promoter proximal position, the HPV-16 P97 and HPV-18 P105 promoters could be transactivated by E2. E2-mediated repression of HPV-18 P105 promoter activity was shown to be a transcriptional effect. The interaction of E2 with promoter-proximal E2-binding sites is likely to be important for the controlled expression of viral genes transcribed from the HPV-16 P97 promoter and the HPV-18 P105 promoter in infected human genital epithelial cells.
273 citations
TL;DR: Fos is a transcriptional regulator that can activate or repress gene expression by way of two separate functional domains that act on distinct regulatory elements.
Abstract: The Fos-Jun complex has been shown to activate transcription through the regulatory element known as the AP-1 binding site. We show that Fos down regulates several immediate-early genes (c-fos, Egr-1, and Egr-2) after mitogenic stimulation. Specifically, we demonstrate that the target for this repression is a sequence of the form CC(A/T)6GG, also known as a CArG box. Whereas Fos bound to the AP-1 site through a domain rich in basic amino acids and associated with Jun via a leucine zipper interaction, mutant Fos proteins lacking these structures were still capable of causing repression. Furthermore, Jun neither enhanced nor inhibited down regulation by Fos. Critical residues required for repression are located within the C-terminal 27 amino acids of c-Fos, since v-Fos and C-terminal truncations of c-Fos did not down regulate. In addition, transfer of 180 c-Fos C-terminal amino acids to Jun conferred upon it the ability to repress. Finally, Fra-1, a Fos-related protein which has striking similarity to Fos in its C-terminal 40 amino acids, also down regulated Egr-1 expression. Thus, Fos is a transcriptional regulator that can activate or repress gene expression by way of two separate functional domains that act on distinct regulatory elements.
213 citations
TL;DR: CREB has a dual function, that of a repressor in the absence of phosphorylation and an activator when phosphorylated by protein kinase A.
Abstract: We have shown that the transcriptional activity of the protooncogene jun (c-jun) promoter is repressed by a transcription factor, the cAMP response element-binding protein (CREB). This repression can be alleviated when CREB is phosphorylated by the catalytic subunit of protein kinase A. Repression cannot be alleviated by a mutant CREB deficient in the protein kinase A phosphorylation site (M1 CREB Ser-133----Ala), suggesting that phosphorylation of CREB at this site is essential for the relief of repression. Repression by CREB requires its binding to the c-jun promoter. In NIH 3T3 cells stably expressing CREB, c-jun is no longer induced by serum, but this repression can be relieved by treatment of the cells with forskolin, an agonist of the adenylate cyclase pathway. Thus, CREB has a dual function, that of a repressor in the absence of phosphorylation and an activator when phosphorylated by protein kinase A.
207 citations
TL;DR: It is proposed that repression of UASG and URSG is mediated by two independent pathways that respond to a common signal generated by growth on glucose.
Abstract: Expression of the GAL1 gene in Saccharomyces cerevisiae is strongly repressed by growth on glucose. We show that two sites within the GAL1 promoter mediate glucose repression. First, glucose inhibits transcription activation by GAL4 protein through UASG. Second, a promoter element, termed URSG, confers glucose repression independently of GAL4. We have localized the URSG sequences responsible for glucose repression to an 87-base-pair fragment located between UASG and the TATA box. Promoters deleted for small (20-base-pair) segments that span this sequence are still subject to glucose repression, suggesting that there are multiple sequences within this region that confer repression. Extended deletions across this region confirm that it contains at least two and possibly three URSG elements. To identify the gene products that confer repression upon UASG and URSG, we have analyzed glucose repression mutants and found that the GAL83, REG1, GRR1, and SSN6 genes are required for repression mediated by both UASG and URSG. In contrast, GAL82 and HXK2 are required only for UASG repression. A mutation designated urr1-1 (URSG repression resistant) was identified that specifically relieves URSG repression without affecting UASG repression. In addition, we observed that the SNF1-encoded protein kinase is essential for derepression of both UASG and URSG. We propose that repression of UASG and URSG is mediated by two independent pathways that respond to a common signal generated by growth on glucose.
174 citations
TL;DR: It is demonstrated that transcription of neu can be strongly repressed by the E1A gene products, and results indicate that E 1A negatively regulates neu gene expression at the transcriptional level by means of a specific DNA element.
Abstract: Amplification/overexpression of the human neu protooncogene has been frequently found in human primary breast and ovarian cancers and is correlated with the number of axillary lymph nodes positive for metastasis in breast cancer patients. Identification of the factors controlling transcription of the neu gene is essential for understanding the mechanisms of neu gene regulation and its role in tumorigenicity. The adenovirus early region 1A (E1A) gene products are pleiotropic transcription regulators of viral and cellular genes and have been identified as a viral suppressor gene for metastasis. Here we demonstrate that transcription of neu can be strongly repressed by the E1A gene products. The 13S and 12S products of E1A gene are effective at repressing neu transcription and the transcriptional repression requires the conserved region 2 of the E1A proteins. The target for E1A repression was localized within a 139-base-pair DNA fragment in the upstream region of the neu promoter. In addition, competition experiments suggest that the sequence TGGAATG, within the 139-base-pair fragment, is an important element for the E1A-induced repression. These results indicate that E1A negatively regulates neu gene expression at the transcriptional level by means of a specific DNA element.
TL;DR: This work has identified a hepatocyte-specific enhancer that is repressed by Tse-1, and a cAMP response element (CRE) which is the target for repression by TSE-1 and the specificity of the enhancer is generated by the combination of these two essential elements, which are fully interdependent.
TL;DR: This repression depends on conserved region 1, one of the transforming domains of E1a, indicating that it is an integral feature of adenovirus transformation, and is a unique property among dominant oncogenes.
TL;DR: In this article, the authors demonstrate that the SRE is the site of regulation of both the induction and repression events of c-fos transcription and show that the inner core of SRE can stabilize the binding of SRF and thereby enhance the transcriptional response to serum.
Abstract: Serum stimulation of quiescent fibroblasts results in a dramatic increase in c-fos transcription that peaks by 15 min and is then rapidly repressed to basal levels within 60 min. Using a nuclear run-on assay to follow directly the kinetics of transcription of mutant c-fos constructs, we demonstrate that the serum response element (SRE) is the site of regulation of both the induction and repression events. This is indicated by the ability of the SRE to mediate c-fos kinetics of induced transcription when fused to a heterologous gene and in the absence of a recognizable TATA element. Functions of the inner core and the outer palindromic arms of the SRE have been determined by mutagenesis. The 14-bp inner core binds the serum response factor (SRF) and is, itself, sufficient to mediate both the induction and shutoff of serum-stimulated transcription. Therefore, SRF and any other factors that regulate the transient kinetics of c-fos transcription require no more than these 14 nucleotides to function. The palindromic outer arms of the SRE stabilize the binding of SRF and thereby enhance the transcriptional response to serum. Autoregulation by the c-fos gene product is not affected by the direct interaction of Fos/Jun complexes with the c-fos promoter and is likely to be mediated by either a novel function of the Fos protein or by an effect of Fos on the expression of another gene.
TL;DR: With germline transformation in mice, a cis-acting element was identified upstream of the transcription initiation site of the alpha-fetoprotein gene that was responsible for repression of the gene in adult liver.
Abstract: Transcription of the mouse alpha-fetoprotein gene is activated in the developing fetal liver and gut and repressed in both tissues shortly after birth. With germline transformation in mice, a cis-acting element was identified upstream of the transcription initiation site of the alpha-fetoprotein gene that was responsible for repression of the gene in adult liver. This negative element acts as a repressor in a position-dependent manner.
TL;DR: Examination of histidase and beta-galactosidase expression in extracts of a hut-lacZ fusion strain grown in various media showed that induction, catabolite repression, and amino acid repression of the hut operon were mediated at the level of transcription.
Abstract: The first enzymes of the histidine (hut) and proline degradative pathways, histidase and proline oxidase, could not be induced in Bacillus subtilis cells growing in glucose minimal medium containing a mixture of 16 amino acids. Addition of the 16-amino-acid mixture to induced wild-type cells growing in citrate minimal medium repressed histidase synthesis 25- to 250-fold and proline oxidase synthesis 16-fold. A strain containing a transcriptional fusion of the hut promoter to the beta-galactosidase gene was isolated from a library of Tn917-lacZ transpositions. Examination of histidase and beta-galactosidase expression in extracts of a hut-lacZ fusion strain grown in various media showed that induction, catabolite repression, and amino acid repression of the hut operon were mediated at the level of transcription. This result was confirmed by measurement of the steady-state level of hut RNA in cells grown in various media. Since amino acid repression was not defective in B. subtilis mutants deficient in nitrogen regulation of glutamine synthetase and catabolite repression, amino acid repression appears to be mediated by a system that functions independently of these regulatory systems.
TL;DR: It is shown that the rapid postinduction decrease in the level of IFN-beta mRNA is due to a combination of transcriptional repression and rapid turnover of the mRNA, which can be blocked with cycloheximide.
Abstract: Viral induction of the human beta-interferon (IFN-beta) gene leads to a transient accumulation of high levels of IFN-beta mRNA. Previous studies have shown that the increase in IFN-beta mRNA levels after induction is due to an increase in the rate of IFN-beta gene transcription. In this paper, we show that the rapid postinduction decrease in the level of IFN-beta mRNA is due to a combination of transcriptional repression and rapid turnover of the mRNA. This transcriptional repression can be blocked with cycloheximide, suggesting that the synthesis of a virus-inducible repressor is necessary for the postinduction turnoff of the IFN-beta gene. Analysis of the sequence requirements for IFN-beta mRNA instability revealed two regions capable of destabilizing a heterologous mRNA. One destabilizer is an AU-rich sequence in the 3' untranslated region, and the other is located 5' to the translation stop codon.
Journal Article•
TL;DR: This review summarizes work aimed at elucidating the molecular mechanisms by which a growth factor-induced signal effects a change in gene expression, including c-fos, where both the activation and repression of transcription are mediated by the serum response element.
Abstract: Many growth factor-inducible immediate-early genes, including c-fos, encode transcription factors that are believed to propagate the mitogenic signal by activating a program of gene expression critical for cell proliferation. This review summarizes work aimed at elucidating the molecular mechanisms by which a growth factor-induced signal effects a change in gene expression. In the case of c-fos, both the activation and repression of transcription are mediated by the serum response element, a dyad symmetrical sequence found upstream of the c-fos gene. This element binds a complex of proteins, a component(s) of which may be the target of the growth factor-induced signal. Recent progress made towards understanding the roles of these factors in the regulation of c-fos transcription will be described.
TL;DR: The results indicate that the amino-terminal region of the protein, which contains domain 1, plays a crucial role in repression, possibly by interfering in the transcriptional activation process at a step common to all trans-acting enhancer factors.
Abstract: It has been shown previously that the adenovirus 2 (Ad2) E1A proteins repress activation of transcription by the SV40, polyomavirus and immunoglobulin gene enhancers. Here, we demonstrate that the repression of the SV40 enhancer is not specifically mediated by one of its constituent enhansons and/or proto-enhancers, but that each is subject to repression individually. This inhibitory effect of the E1A proteins is also observed with the AP-1 factor-binding enhansons from the polyomavirus and human metallothionein enhancers, and the MHC class I gene H-2Kb enhanson, which binds the KBF1/H2TF1/TC-IIB protein. Repression by the E1A gene products may, in fact, extend to all enhancer trans-activators, because the transcriptional activities of nuclear receptors (e.g., the estrogen and glucocorticoid receptors), of the yeast enhancer factor GAL4 expressed in HeLa cells, and of chimeric trans-activators (such as GAL-VP16) are all similarly inhibited. The E1A protein domains 2 and 3, including the acidic amino acid stretch that has been shown previously to be necessary for E1A-mediated trans-activation, are not required for repression. These results indicate that the amino-terminal region of the protein, which contains domain 1, plays a crucial role in repression, possibly by interfering in the transcriptional activation process at a step common to all trans-acting enhancer factors.
TL;DR: Results indicate the presence of a stem cell-specific repressor that extinguishes M-MuLV expression via the NRE at the tRNA PBS via base-pair mutagenesis to an 18-base-pair segment of the t RNA PBS.
Abstract: A negative regulatory element (NRE) spanning the tRNA primer-binding site (PBS) of Moloney murine leukemia virus (M-MuLV) mediates repression of M-MuLV expression specifically in embryonal carcinoma (EC) cells. We precisely defined the element by base-pair mutagenesis to an 18-base-pair segment of the tRNA PBS and showed that the element also restricted expression when moved upstream of the long terminal repeat. A DNA-binding activity specific for the M-MuLV NRE was detected in vitro by using crude EC nuclear extracts in exonuclease III protection assays. Binding was strongly correlated with repression in EC cells. Mutations within the NRE that relieved repression disrupted binding activity. Also, nuclear extracts prepared from permissive, differentiated EC cell cultures showed reduced binding activity for the NRE. These results indicate the presence of a stem cell-specific repressor that extinguishes M-MuLV expression via the NRE at the tRNA PBS.
TL;DR: It is proposed that developmental induction results in a generalized metabolic shutdown, leading to an inability of cells to acquire nutrients from the growth medium, and self-imposed nutrient limitation could reinforce the primary developmental stimulus and ensure progression through the asexual reproductive pathway.
Abstract: Asexual reproductive development can be initiated in Aspergillus nidulans in the presence of excess nutrients through artificial induction of the developmental regulatory genes brlA or abaA by fusing the genes to the promoter from the alcohol dehydrogenase I gene (alcA) and culturing cells in the presence of an inducing alcohol. Artificially induced development completely inhibits growth and represses expression of the endogenous alcA gene and the coordinately controlled aldehyde dehydrogenase gene (aldA). Repression of alcA and aldA expression probably occurs at both the transcriptional and posttranslational levels. We propose that developmental induction results in a generalized metabolic shutdown, leading to an inability of cells to acquire nutrients from the growth medium. Self-imposed nutrient limitation could reinforce the primary developmental stimulus and ensure progression through the asexual reproductive pathway.
TL;DR: This chapter describes the transcriptional and translational regulatory events that involve in the general amino-acid control of S. cerevisiae, which responds to limitation for a single amino acid by increasing the size of many different amino- acid pools.
Abstract: Publisher Summary This chapter describes the transcriptional and translational regulatory events that involve in the general amino-acid control of S. cerevisiae. General-control-mediated derepression of certain lysine biosynthetic enzymes is also partially over-ridden by a lysine-specific repression mechanism when lysine is not limiting. The same phenomenon may apply to certain leucine biosynthetic enzymes that are subject to leucine-specific repression. By contrast, multivalent repression of enzymes in the isoleucine-valine pathway by a mixture of isoleucine, valine, and leucine does not interfere with their derepression by the general control system in response to starvation for other amino acids. Smaller increases have been observed for the leucine and glutamate pools. It is not obvious why S. cerevisiae responds to limitation for a single amino acid by increasing the size of many different amino-acid pools. Perhaps single amino-acid limitation occurs rarely in nature, such that multiple-pathway derepression is generally a simple and effective response to starvation conditions, with specific repression mechanisms operating to over-ride derepression of those pathways for which no amino-acid limitation exists.
TL;DR: It is proposed that the postinduction repression of beta-IFN gene transcription involves virus-inducible repressors that either bind directly to the positive regulatory elements of the beta- IFN promoter or inactivate thepositive regulatory factors bound to PRDI and PRDII.
Abstract: Virus induction of the human beta-interferon (beta-IFN) gene results in an increase in the rate of beta-IFN mRNA synthesis, followed by a rapid postinduction decrease. In this paper, we show that two beta-IFN promoter elements, positive regulatory domains I and II (PRDI and PRDII), which are required for virus induction of the beta-IFN gene are also required for the postinduction turnoff. Although protein synthesis is not necessary for activation, it is necessary for repression of these promoter elements. Examination of nuclear extracts from cells infected with virus reveals the presence of virus-inducible, cycloheximide-sensitive, DNA-binding activities that interact specifically with PRDI or PRDII. We propose that the postinduction repression of beta-IFN gene transcription involves virus-inducible repressors that either bind directly to the positive regulatory elements of the beta-IFN promoter or inactivate the positive regulatory factors bound to PRDI and PRDII.
TL;DR: It is suggested that the mRNA contains functionally distinct ribosome and repressor binding sites that are allosterically coupled and can relieve translational repression by disrupting the linkage between the two sites without altering S4 binding.
Abstract: Escherichia coli ribosomal protein S4 is a translational repressor regulating the expression of four ribosomal genes in the alpha operon In vitro studies have shown that the protein specifically recognizes an unusual mRNA pseudoknot secondary structure which links sequences upstream and downstream of the ribosome binding site for rpsM (S13) [Tang, C K, & Draper, D E (1989) Cell 57, 531] We have prepared fusions of the rpsM translational initiation site and lacZ that allows us to detect repression in cells in which overproduction of S4 repressor can be induced Twenty-five mRNA sequence variants have been introduced into the S13-lacZ fusions and the levels of translational repression measured Sets of compensating base changes confirm the importance of the pseudoknot secondary structure for translational repression An A residue in a looped, single-stranded sequence is also required for S4 recognition and may contact S4 directly Comparison of translational repression levels and S4 binding constants for the set of mRNA mutations show that nine mutants are repressed much more weakly than predicted from their affinity for S4; in extreme cases no repression can be detected for variants with unchanged S4 binding We suggest that the mRNA contains functionally distinct ribosome and repressor binding sites that are allosterically coupled Mutations can relieve translational repression by disrupting the linkage between the two sites without altering S4 binding This proposal assigns to the mRNA a more active role in mediating translational repression than found in other translational repression systems
TL;DR: Using the comparatively drastic and synchronous response to fungal elicitor, it is demonstrated that the repression of SSU synthesis was caused by rapid gene inactivation and supports the hypothesis that induction of the extensive, multi-component defense response requires repression of other cellular functions to ensure metabolic balance.
Abstract: The levels of ribulose 1,5-bisphosphate carboxylase small-subunit (SSU) mRNA and protein decreased considerably in potato (Solanum tuberosum L.) leaves upon infection with the pathogenic fungus,Phytophthora infestans, or upon treatment with an elicitor preparation from the fungal culture fluid. This effect occurred systemically throughout the affected leaf, regardless of whether the interaction withP. infestans was compatible or incompatible. Using the comparatively drastic and synchronous response to fungal elicitor, we demonstrated that the repression of SSU synthesis was caused by rapid gene inactivation. The timing of repression was similar to that observed previously for the transcriptional activation of various pathogen defense reactions. This supports the hypothesis that induction of the extensive, multi-component defense response requires repression of other cellular functions to ensure metabolic balance.
TL;DR: A normal part of transcriptional regulation of the GAL1 and GAL10 genes appears to involve a balance between the opposing functions of positive and negative control elements.
Abstract: The yeast GAL1 and GAL10 genes are transcribed at a remarkably low basal level when galactose is unavailable and are induced by over 4 orders of magnitude when it becomes available. Approximately six negative control elements (designated GAL operators GALO1 to GALO6) are located adjacent to or overlapping four binding sites for the transcription activator GAL4 in the GAL upstream activating sequence UASG. The negative control elements contribute to the broad range of inducibility of GAL1 and GAL10 by inhibiting two GAL4/galactose-independent activating elements (GAE1 and GAE2) in UASG. In turn, multiple GAL4-binding sites in UASG are necessary for GAL4 to overcome repression by the negative control elements under fully inducing conditions. When glucose in addition to galactose is available (repressing conditions), the ability of GAL4 to activate transcription is diminished as a result of its reduced affinity for DNA and the reduced availability of inducer. Under these conditions, the negative control elements inhibit transcriptional activation from the glucose-attenuated GAL4 sites, thus accounting at least in part for glucose repression acting in cis. A normal part of transcriptional regulation of the GAL1 and GAL10 genes, therefore, appears to involve a balance between the opposing functions of positive and negative control elements.
TL;DR: All seven lines derived from a strain called Sexi possessed numerous copies of a particular P element, called KP, which has been hypothesized to produce a polypeptide repressor of gonadal dysgenesis, but this hypothesis does not explain why the inbred Sexi lines varied so much in their repression abilities.
Abstract: Inbred lines derived from a strain called Sexi were analyzed for their abilities to repress P element-mediated gonadal dysgenesis. One line had high repression ability, four had intermediate ability and two had very low ability. The four intermediate lines also exhibited considerable within-line variation for this trait; furthermore, in at least two cases, this variation could not be attributed to recurring P element movement. Repression of gonadal dysgenesis in the hybrid offspring of all seven lines was due primarily to a maternal effect; there was no evidence for repression arising de novo in the hybrids themselves. In one of the lines, repression ability was inherited maternally, indicating the involvement of cytoplasmic factors. In three other lines, repression ability appeared to be determined by partially dominant or additive chromosomal factors; however, there was also evidence for a maternal effect that reduced the expression of these factors in at least two of the lines. In another line, repression ability seemed to be due to recessive chromosomal factors. All seven lines possessed numerous copies of a particular P element, called KP, which has been hypothesized to produce a polypeptide repressor of gonadal dysgenesis. This hypothesis, however, does not explain why the inbred Sexi lines varied so much in their repression abilities. It is suggested that some of this variation may be due to differences in the chromosomal position of the KP elements, or that other nonautonomous P elements are involved in the repression of hybrid dysgenesis in these lines.
TL;DR: Deletion analysis of a DNA fragment carrying a DNA segment containing a sequence, ATTGAAAG, which may be implicated as a consensus sequence involved in catabolite repression in the genus Bacillus, revealed that this sequence is located between nucleotide positions +137 and +148.
Abstract: The mechanism underlying catabolite repression in Bacillus species remains unsolved. The gluconate (gnt) operon of Bacillus subtilis is one of the catabolic operons which is under catabolite repression. To identify the cis sequence involved in catabolite repression of the gnt operon, we performed deletion analysis of a DNA fragment carrying the gnt promoter and the gntR gene, which had been cloned into the promoter probe vector, pWP19. Deletion of the region upstream of the gnt promoter did not affect catabolite repression. Further deletion analysis of the gnt promoter and gntR coding region was carried out after restoration of promoter activity through the insertion of internal constitutive promoters of the gnt operon before the gntR gene (P2 and P3). These deletions revealed that the cis sequence involved in catabolite repression of the gnt operon is located between nucleotide positions +137 and +148. This DNA segment contains a sequence, ATTGAAAG, which may be implicated as a consensus sequence involved in catabolite repression in the genus Bacillus.
TL;DR: Further analysis revealed that UAS1(5b) is the site of carbon source control and may be composed of two distinct domains that act synergistically and URS5b mediates the aerobic repression of COX5b and contains two sequences that are highly conserved in other yeast genes negatively regulated by oxygen.
Abstract: The Saccharomyces cerevisiae COX5b gene is regulated at the level of transcription by both the carbon source and oxygen. To define the cis-acting elements that underlie this transcriptional control, deletion analysis of the upstream regulatory region of COX5b was performed. The results of the study suggest that at least four distinct regulatory sites are functional upstream of the COX5b transcriptional starts. One, which was precisely defined to a region of 20 base pairs, contains two TATA-like elements. Two upstream activating sequences (UAS15b and UAS2(5b)) and an upstream repression sequence (URS5b) were also found. Each of the latter three elements was able either to activate (UAS1(5b) and UAS2(5b)) or to repress URS5b) the transcription of a heterologous yeast gene. Further analysis revealed that UAS1(5b) is the site of carbon source control and may be composed of two distinct domains that act synergistically. URS5b mediates the aerobic repression of COX5b and contains two sequences that are highly conserved in other yeast genes negatively regulated by oxygen.
TL;DR: The data indicate that LAC9 is a limiting factor for beta-galactosidase gene expression under all growth conditions and that glucose reduces the activity of the activator.
Abstract: The transcriptional activator LAC9, a GAL4 homolog of Kluyveromyces lactis which mediates lactose and galactose-dependent activation of genes involved in the utilization of these sugars can also confer glucose repression to those genes. Here we report on the isolation and characterization of LAC9-2, an allele which encodes a glucose-sensitive activator in contrast to the one previously cloned. A single amino acid exchange of leu-104 to tryptophan is responsible for the glucose-insensitive phenotype. The mutation is located within the Zn-finger-like DNA binding domain which is highly conserved between LAC9 and GAL4. Glucose repression is also eliminated by duplication of the LAC9-2 allele. The data indicate that LAC9 is a limiting factor for beta-galactosidase gene expression under all growth conditions and that glucose reduces the activity of the activator.