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At least 271 records · Page 15Linked to original sources
PubMed1997

Posttranscriptional regulation of collagen alpha1(I) mRNA in hepatic stellate cells.

The hepatic stellate cell (HSC) is the primary cell responsible for the dramatic increase in the synthesis of type I collagen in the cirrhotic liver. Quiescent HSCs contain a low level of collagen alpha1(I) mRNA, while activated HSCs contain about 60- to 70-fold more of this mRNA. The transcription rate of the collagen alpha1(I) gene is only two fold higher in activated HSCs than in quiescent HSCs. In assays using actinomycin D or 5,6-dichlorobenzimidazole riboside collagen alpha1(I) mRNA has estimated half-lives of 1.5 h in quiescent HSCs and 24 h in activated HSCs. Thus, this 16-fold change in mRNA stability is primarily responsible for the increase in collagen alpha1(I) mRNA steady-state level in activated HSCs. We have identified a novel RNA-protein interaction targeted to the C-rich sequence in the collagen alpha1(I) mRNA 3' untranslated region (UTR). This sequence is localized 24 nucleotides 3' to the stop codon. In transient transfection experiments, mutation of this sequence diminished accumulation of an mRNA transcribed from a collagen alpha1(I) minigene and in stable transfections decreased the half-life of collagen alpha1(I) minigene mRNA. Binding to the collagen alpha1(I) 3' UTR is present in cytoplasmic extracts of activated but not quiescent HSCs. It contains as a subunit alphaCP, which is also found in the complex involved in stabilization of alpha-globin mRNA. The auxiliary factors necessary to promote binding of alphaCP to the collagen 3' UTR are distinct from the factors necessary for binding to the alpha-globin sequence. Since alphaCP is expressed in both quiescent and activated HSCs, these auxiliary factors are responsible for the differentially expressed RNA-protein interaction at the collagen alpha1(I) mRNA 3' UTR.

Animals↗
PubMed1999

Regulation of nuclear localization and transcriptional activity of TFII-I by Bruton's tyrosine kinase.

Bruton's tyrosine kinase (Btk) is required for normal B-cell development, as defects in Btk lead to X-linked immunodeficiency (xid) in mice and X-linked agammaglobulinemia (XLA) in humans. Here we demonstrate a functional interaction between the multifunctional transcription factor TFII-I and Btk. Ectopic expression of wild-type Btk enhances TFII-I-mediated transcriptional activation and its tyrosine phosphorylation in transient-transfection assays. Mutation of Btk in either the PH domain (R28C, as in the murine xid mutation) or the kinase domain (K430E) compromises its ability to enhance both the tyrosine phosphorylation and the transcriptional activity of TFII-I. TFII-I associates constitutively in vivo with wild-type Btk and kinase-inactive Btk but not xid Btk. However, membrane immunoglobulin M cross-linking in B cells leads to dissociation of TFII-I from Btk. We further show that while TFII-I is found in both the nucleus and cytoplasm of wild-type and xid primary resting B cells, nuclear TFII-I is greater in xid B cells. Most strikingly, receptor cross-linking of wild-type (but not xid) B cells results in increased nuclear import of TFII-I. Taken together, these data suggest that although the PH domain of Btk is primarily responsible for its physical interaction with TFII-I, an intact kinase domain of Btk is required to enhance transcriptional activity of TFII-I in the nucleus. Thus, mutations impairing the physical and/or functional association between TFII-I and Btk may result in diminished TFII-I-dependent transcription and contribute to defective B-cell development and/or function.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed2006

Molecular mechanisms involved in the adaptive regulation of human intestinal biotin uptake: A study of the hSMVT system.

Biotin, a water-soluble micronutrient, is vital for cellular functions, including growth and development. The human intestine utilizes the human sodium-dependent multivitamin transporter (hSMVT) for biotin uptake. Evidence exists showing that the intestinal biotin uptake process is adaptively regulated during biotin deficiency. Nothing, however, is known about molecular mechanism(s) involved during this adaptive regulation. This study compared two human-derived intestinal epithelial cell lines (HuTu-80 and Caco-2) during biotin-deficient or biotin-sufficient states and with an approach that assessed carrier-mediated biotin uptake, hSMVT protein and RNA levels, RNA stability, and hSMVT promoter activity. The results showed that during biotin deficiency, a significant and specific upregulation in carrier-mediated biotin uptake occurred in both human intestinal epithelial cell lines and that this increase was associated with an induction in protein and mRNA levels of hSMVT. The increase in mRNA levels was not due to an increase in RNA stability but was associated with an increase in activity of the hSMVT promoter in transfected human intestinal cells. Using promoter deletion constructs and mutational analysis in transiently transfected HuTu-80 and Caco-2 cells, a biotin deficiency-responsive region was mapped to a 103-bp area within the hSMVT promoter that contains gut-enriched Kruppel-like factor (GKLF) sites that confer the response to biotin deficiency. These results confirm that human intestinal biotin uptake is adaptively regulated and provide novel evidence demonstrating that the upregulation is not mediated via changes in hSMVT RNA stability but rather is due to transcriptional regulatory mechanism(s) that likely involve GKLF sites in the hSMVT promoter.

Actins↗
PubMedDate not supplied

Cloning and characterization of the human lung endothelial-cell-specific molecule-1 promoter.

Endothelial-cell-specific molecule-1 (ESM-1) is a cysteine-rich protein that is expressed primarily in endothelial cells of the lung, kidney and gut. In the present study, we have cloned and sequenced 3,888 bp of the 5' flanking region of the human ESM-1 gene. The full-length promoter directed high-level expression of the luciferase reporter gene in bovine lung microvascular endothelial cells and bovine aortic endothelial cells, but not in nonendothelial cell types. In 5' deletion analyses, a region spanning -81 to +58 was shown to contain information for endothelial-cell-specific expression. Mutational analysis in transient transfection assays uncovered an important role for an Ets-binding motif located between -77 and -74 and a cAMP-response-element (CRE)-like motif located between -68 and -62 in mediating high-level expression in endothelial cells. A second Ets site (-63 to -60) as well as a novel 6-bp palindromic sequence (-58 to -53) were found to inhibit expression. In DNase footprint analyses, both the Ets-binding motifs were protected specifically in endothelial cells, while the CRE-like element and palindrome were protected in endothelial and nonendothelial cells alike. Taken together, these results provide an important foundation for studying endothelial-cell-subtype-specific gene regulation.

Animals↗
PubMed2000

Identification of an essential cis-acting element (TR2-PACE) in the 5' promoter of human TR2 orphan receptor gene.

The human TR2 orphan receptor (TR2) is a member of the steroid/thyroid hormone receptor superfamily. It has been shown to be expressed in a wide variety of tissues during development. Using deletion mutation analyses and transient transfection CAT assays, we demonstrated here that a DNA fragment of 103 bp, with a sequence from +65 to -38, containing an initiator is capable of serving as a core promoter to initiate basal level transcription; further extending of this core promoter sequence up to -441 maximizes the reporter gene expression. Within this positive regulatory region (-441/+65), we were able to narrow the regulation-responsible sequence down to a small 64-bp (-263/-201) DNA fragment named the TR2 promoter activating cis-element (TR2-PACE). Further deletion mutagenesis and shifting of the insert position followed by reporter assays demonstrated that this TR2-PACE is essential for high-level induction of a heterologous core promoter's activity in a position-dependent nature. In addition, orientation tests indicated that the sense, but not antisense orientation increased the TR2 core promoter activity. Moreover, electrophoresis mobility shift assays and Southwestern analyses suggested that TR2-PACE may interact with unknown specific nuclear proteins for its enhancer activity. Together, our data suggest that TR2-PACE is a position-dependent and, in the case of TR2 core promoter (TATA-less), an orientation-dependent cis-activating element required for maximal expression of the TR2 gene.

Base Sequence↗
PubMed2006

Antisense p53 decreases production of VEGF in follicular thyroid cancer cells.

Inactivating mutations of wild-type p53 (WTp53) tumor suppressor gene are common in anaplastic thyroid cancer (ATC) and are associated with poor prognosis. Mutated p53 (MTp53) has been implicated with angiogenesis. Therefore, the potential of MTp53 knockout by oligodeoxyribonucleotide phosphorothioates (ODNs) to affect VEGF production of undifferentiated thyroid cancer cells with a recessive MTp53 mutation was evaluated. Transient transfection with 20 bp ODNs complementary to portions of exon 10 of p53 and a negative control ODN (HIV-RT) were carried out in FTC-133 cells. In vitro secretion of VEGF protein was quantified by EIA and correlated to cell numbers, which was evaluated by in vitro MTT assay. Transfection of undifferentiated thyroid cancer cells with ODN reduced VEGF secretion of FTC-133 cells following transfection by 34% as compared to the negative control (cells transfected with ODN-HIV; p = 0.03). These results suggest that transient MTp53 knockout with ODNs complementary to p53 nucleotide sequences impair secretion of VEGF in the undifferentiated thyroid cancer cell line FTC-133.

Adenocarcinoma, Follicular↗
PubMed2004

Olfactory sex discrimination persists, whereas the preference for urinary odorants from estrous females disappears in male mice after vomeronasal organ removal.

Based on observed changes in the social context for the display of ultrasonic vocalizations, scent marking, aggression, and mounting behavior by male mice with a null mutation of the transient receptor potential 2 ion channel, it was proposed recently that a primary function of the mouse vomeronasal organ (VNO)/accessory olfactory system is sex discrimination. We tested this hypothesis directly by studying the ability of male mice to discriminate between urinary odors of conspecifics of the two sexes and in different endocrine states using habituation-dishabituation tests. Male mice from which the VNO had been surgically removed (VNOx) resembled sham-operated controls (VNOi) in their ability to discriminate between volatile urinary odors from estrous females versus gonadally intact males, as well as between urinary odors from estrous versus ovariectomized females and from gonadally intact versus castrated males. When physical access to stimuli was permitted, VNOi control males strongly preferred to investigate volatile and nonvolatile urinary odorants from estrous females as opposed to intact males, whereas VNOx males showed no such preference. Mating performance in tests with estrous females was equivalent in VNOi and VNOx subjects. Both groups of males preferred to mount an estrous female instead of a castrated male. Our results suggest that the VNO is not required for sex discrimination but instead detects the nonvolatile components of opposite-sex urine that may be used to help prolong contact with individuals that produce these chemosignals.

Animals↗
PubMed2004

YY1 binding within the human HSD3B2 gene intron 1 is required for maximal basal promoter activity: identification of YY1 as the 3beta1-A factor.

The oxidation and isomerization of 3beta-hydroxy-5-ene steroids into keto-4-ene steroids, a pivotal step in the synthesis of all hormonal steroids, is catalyzed by several isoforms of 3beta-hydroxysteroid dehydrogenase. In humans, two highly homologous isoforms exist, type I expressed by the HSD3B1 gene in peripheral tissues, and type II expressed by the HSD3B2 gene in steroidogenic organs. Previously, it was shown that the HSD3B1 gene 3beta1-A element, encompassing 24 nucleotides of intron 1 not perfectly conserved between the two genes and overlapping with a conserved TG box, contributes to maximal basal promoter activity by binding the ubiquitous and unidentified 3beta1-A transcription factor. In this study for the first time we report that similarly, the HSD3B2 gene intron 1 is required for maximal basal promoter activity in reporter gene analyses, as lack of intron 1 results in a 4- to 10-fold reduction in promoter activity. Mutational analysis in gel shift assays revealed that the 3beta1-A factor binds both the HSD3B2 and HSD3B1 gene intron 1 by requiring only seven nucleotides of a conserved segment within the 3beta1-A element. By competition analysis and use of anti-YY1 antibody in both gel shift and Western blot experiments, we identified the 3beta1-A protein as the ubiquitous transcription factor YY1. In addition, we have characterized another similar YY1 binding site differently located with respect to the 3beta1-A element in both genes. Deletion and mutational analysis in transient transfections experiments revealed that contrarily to as previously shown for the HSD3B1 gene, lack of YY1 binding to the type II 3beta1-A element only results in a marginal reduction of basal promoter activity. Instead, YY1 binding to the second site, placed 35 bp downstream from the 3beta1-A element, strongly activates the HSD3B2 gene basal promoter activity, as preventing YY1 binding to this region caused a 50% decrease of basal transcription. Complete abrogation of YY1 binding within type II intron 1 resulted in a gene reporter activity identical to a reporter construct lacking the whole intron 1. These results designate YY1 as the factor responsible for the intron 1-mediated boost of the HSD3B2 gene basal promoter activity. Similarities and dissimilarities between YY1 binding within the HSD3B1 and HSD3B2 gene intron 1 are discussed involving the conserved intron 1 TG box, that suggests different mechanisms are implicated in the YY1-mediated stimulation of these two genes basal promoter activity.

3-Hydroxysteroid Dehydrogenases↗
PubMed2000

NUC-1, a caenorhabditis elegans DNase II homolog, functions in an intermediate step of DNA degradation during apoptosis.

One hallmark of apoptosis is the degradation of chromosomal DNA. We cloned the Caenorhabditis elegans gene nuc-1, which is involved in the degradation of the DNA of apoptotic cells, and found that nuc-1 encodes a homolog of mammalian DNase II. We used the TUNEL technique to assay DNA degradation in nuc-1 and other mutants defective in programmed cell death and discovered that TUNEL labels apoptotic cells only during a transient intermediate stage. Mutations in nuc-1 allowed the generation of TUNEL-reactive DNA but blocked the conversion of TUNEL-reactive DNA to a subsequent TUNEL-unreactive state. Completion of DNA degradation did not occur in the absence of cell-corpse engulfment. Our data suggest that the process of degradation of the DNA of a cell corpse occurs in at least three distinct steps and requires activities provided by both the dying and the engulfing cell.

Animals↗
PubMed2000

Characterization of rat liver malonyl-CoA decarboxylase and the study of its role in regulating fatty acid metabolism.

In the liver, malonyl-CoA is central to many cellular processes, including both fatty acid biosynthesis and oxidation. Malonyl-CoA decarboxylase (MCD) is involved in the control of cellular malonyl-CoA levels, and functions to decarboxylate malonyl-CoA to acetyl-CoA. MCD may play an essential role in regulating energy utilization in the liver by regulating malonyl-CoA levels in response to various nutritional or pathological states. The purpose of the present study was to investigate the role of liver MCD in the regulation of fatty acid oxidation in situations where lipid metabolism is altered. A single MCD enzyme of molecular mass 50.7 kDa was purified from rat liver using a sequential column chromatography procedure and the cDNA was subsequently cloned and sequenced. The liver MCD cDNA was identical to rat pancreatic beta-cell MCD cDNA, and contained two potential translational start sites, producing proteins of 50.7 kDa and 54.7 kDa. Western blot analysis using polyclonal antibodies generated against rat liver MCD showed that the 50.7 kDa isoform of MCD is most abundant in heart and liver, and of relatively low abundance in skeletal muscle (despite elevated MCD transcript levels in skeletal muscle). Tissue distribution experiments demonstrated that the pancreas is the only rat tissue so far identified that contains both the 50.7 kDa and 54. 7 kDa isoforms of MCD. In addition, transfection of the full-length rat liver MCD cDNA into COS cells produced two isoforms of MCD. This indicated either that both initiating methionines are functionally active, generating two proteins, or that the 54.7 kDa isoform is the only MCD protein translated and removal of the putative mitochondrial targeting pre-sequence generates a protein of approx. 50.7 kDa in size. To address this, we transiently transfected a mutated MCD expression plasmid (second ATG to GCG) into COS-7 cells and performed Western blot analysis using our anti-MCD antibody. Western blot analysis revealed that two isoforms of MCD were still present, demonstrating that the second ATG may not be responsible for translation of the 50.7 kDa isoform of MCD. These data also suggest that the smaller isoform of MCD may originate from intracellular processing. To ascertain the functional role of the 50. 7 kDa isoform of rat liver MCD, we measured liver MCD activity and expression in rats subjected to conditions which are known to alter fatty acid metabolism. The activity of MCD was significantly elevated under conditions in which hepatic fatty acid oxidation is known to increase, such as streptozotocin-induced diabetes or following a 48 h fast. A 2-fold increase in expression was observed in the streptozotocin-diabetic rats compared with control rats. In addition, MCD activity was shown to be enhanced by alkaline phosphatase treatment, suggesting phosphorylation-related control of the enzyme. Taken together, our data demonstrate that rat liver expresses a 50.7 kDa form of MCD which does not originate from the second methionine of the cDNA sequence. This MCD is regulated by at least two mechanisms (only one of which is phosphorylation), and its activity and expression are increased under conditions where fatty acid oxidation increases.

Alkaline Phosphatase↗
PubMed1992

A common set of nuclear factors bind to promoter elements regulated by the retinoblastoma protein.

A 30-base pair element within the c-fos promoter, termed the RCE (retinoblastoma control element), has previously been shown to be the target of transcriptional regulation by the product of the retinoblastoma (Rb) gene. We have identified three nuclear proteins [retinoblastoma control proteins (RCPs)] that complex with this promoter element in vitro. The Rb gene does not appear to encode the RCPs as the expression of Rb in vivo does not correlate with RCE-RCP complex formation in vitro. A single binding site for the RCPs within the c-fos RCE was identified, and the nucleotides required for protein-DNA complex formation were defined. Similar sequences are found in the promoters of two additional genes that are regulated by Rb (c-myc and TGF-beta 1), and binding assays demonstrate that the RCPs also interact with these elements. Linkage of the c-fos RCE to the herpes simplex virus thymidine kinase promoter led to a 4-fold stimulation of expression in transient transfection assays. Mutations within the RCP binding site that abrogate stable interaction of the RCPs with the RCE in vitro block RCE transcriptional activity in vivo. Our results suggest a role for the RCPs in RCE-dependent transcription and the regulation of transcription by the Rb protein.

Base Sequence↗
PubMed2005

GM1 expression in H-ras-transformed NIH3T3 results in the suppression of cell proliferation inducing the partial transfer of activated H-ras from non-raft to raft fraction.

c-H-ras is located in lipid/rafts and undergoes cholesterol dependent regulation. To analyze the regulatory effects of ganglioside GM1 on the proliferation of fibroblasts transformed with mutated ras gene, GM1 synthase cDNA was transfected into NIH3T3/H-ras cells containing mutation. In the transient expression system with EGFP-fused GM1 synthase, the ratio of BrdU-positive cells among EGFP-positive cells was compared between GM1(+) transfectant cells and control cells, indicating that the transient GM1 expression suppresses cell proliferation. Then, established transfectant cells C21 and C34 expressed definite levels of GM1, and analyzed for the cell growth with the control cells D2 and D4 expressing no GM1. GM1(+) cells showed reduced proliferation compared with controls. Phosphorylation levels of ERK1/2 after FCS treatment were examined, showing that those on the GM1(+) transfectant cells increased slowly, while those in the controls rapidly reached the plateau. Fractionation of Triton X-100 extracts with sucrose density gradient ultra-centrifugation revealed that activated H-ras proteins from controls as well as NIH3T3/H-ras were completely localized in non-GEM/raft fraction. On the other hand, some portions of activated H-ras were transferred to GEM/raft fraction, i.e., 32% in C21, and 8% in C34. Since the Ras effector Raf-1 was localized in non-GEM/raft, the growth suppression might be caused, at least partly, by the movement of activated H-ras to GEM/raft fraction.

Animals↗
PubMed1994

G alpha 13 stimulates Na-H exchange.

Activity of the ubiquitous Na-H exchanger (NHE1) is regulated by a number of receptors with tyrosine kinase activity as well as by several classes of receptors coupled to heterotrimeric GTP-binding proteins. We previously demonstrated that the beta 2-adrenergic receptor and other receptors that stimulate adenylyl cyclase by activating Gs stimulate NHE1 by a guanine nucleotide-dependent mechanism that is independent of receptor coupling to Gs. Now we report that a recently identified G alpha subunit, alpha 13, activates the exchanger. Transient expression of mutationally activated alpha 13 constitutively stimulates Na-H exchange; moreover, an alpha 13/alpha z chimera, designed to respond to stimulation by Gi-coupled receptors, mediates stimulation of Na-H exchange by one such receptor, the dopamine2 receptor. Mutationally activated alpha 13, however, does not stimulate adenylyl cyclase activity or phosphoinositide hydrolysis, indicating that its action on NHE1 occurs independently of these two effector pathways. These findings reveal the first known signaling function of alpha 13 and identify a new G protein involved in the regulation of NHE1.

Amino Acid Sequence↗
PubMed1994

Definition of the carbohydrate response element of the rat S14 gene. Context of the CACGTG motif determines the specificity of carbohydrate regulation.

Transcription of the S14 gene in primary hepatocytes is stimulated in response to increased carbohydrate metabolism. We have demonstrated previously that a 30-base pair (bp) segment of the S14 gene from -1457 to -1428 is a carbohydrate response element (ChoRE). This element contains a (5')CACGTG motif that is essential for control. DNase I footprinting experiments with liver nuclear extract revealed two factors binding within the S14 ChoRE. In transient transfection experiments, mutation of the upstream site between -1457 and -1450 did not affect the response to elevated glucose, whereas the downstream 21-bp site between -1448 and -1428 was sufficient to mediate the glucose induction. Electrophoretic mobility shift assays indicated that the hepatic factor binding to this site in vitro is closely related or identical to the major late transcription factor (MLTF). However, replacement of the 21-bp S14 ChoRE with the authentic MLTF binding site from the adenovirus major late promoter failed to elicit the glucose response. By systematically exchanging bases between the functional S14 and nonresponsive adenovirus sites, the sequence (5')CACGTGNNNGCC was found to be essential for carbohydrate regulation. A segment containing this specific motif from the rat fatty acid synthase gene, another carbohydrate-responsive gene in hepatocytes, conferred a carbohydrate response when linked to the S14 promoter. Thus, the context of the CACGTG motif provides the specificity for regulation by carbohydrate metabolism.

Animals↗
PubMed2006

Homozygosity for TNSALP mutation 1348c>T (Arg433Cys) causes infantile hypophosphatasia manifesting transient disease correction and variably lethal outcome in a kindred of black ancestry.

OBJECTIVE: To determine the "tissue-nonspecific" isoenzyme of alkaline phosphatase (TNSALP) defect underlying transiently reversible and variably lethal infantile hypophosphatasia (HPP) in a kindred and to characterize HPP prevalence in black people. STUDY DESIGN: In 1986, we reported temporary correction of severe HPP in an American kindred of black ancestry where "infantile" HPP was fatal in 2 of 3 affected individuals representing 2 sibships. This transient improvement in 1 patient followed efforts to increase TNSALP activity endogenously and suggested dysregulation of the gene (TNSALP). Here, we sequenced the coding exons and splice sites of the kindred's TNSALP alleles and reviewed our 30-year experience with HPP to assess its prevalence in black people. RESULTS: Homozygosity for TNSALP missense mutation 1348C>T (Arg433Cys) accounted for this kindred's infantile HPP. The TNSALP promoter sequence was normal. Modeling of TNSALP(433Cys) suggested compromise of the catalytic site. Ethnicity was identified for the 119 families with HPP studied in St. Louis, and race was ascertained for an additional 159 of our 235 consult and HPP families worldwide. In this experience, only this family was of black ancestry. CONCLUSIONS: Infantile HPP from homozygous TNSALP(433Cys) can remit and thus harbor clues regarding the phenotypic variation and perhaps treatment of HPP.

Black or African American↗
PubMed1998

A patient homozygous for mutation 20210A in the prothrombin gene with venous thrombosis and transient ischemic attacks of thrombotic origin.

It is well established that genetic disorders interact with environmental factors to cause thrombotic diseases. Therefore, antithrombin, protein C, protein S deficiencies and the more recently described factor V Leiden and prothrombin mutations are currently been investigated to explain some thrombophilic states. We report the case of a 63-year-old man who developed two transient ischemic attacks and two years later an extensive femoro-iliac venous thrombosis. He was genotyped as FV R506Q negative and FII G20210A positive in homozygous state (FII 20210AA).

Aged↗
PubMed1999

Selective effects of neuronal-synaptobrevin mutations on transmitter release evoked by sustained versus transient Ca2+ increases and by cAMP.

Synaptobrevin is a key constituent of the synaptic vesicle membrane. The neuronal-synaptobrevin (n-syb) gene in Drosophila is essential for nerve-evoked synaptic currents, but miniature excitatory synaptic currents (mESCs) remain even in the complete absence of this gene. To further characterize the defect in these mutants, we have examined conditions that stimulate secretion. Despite the inability of an action potential to trigger fusion, high K+ saline could increase the frequency of mESCs 4- to 17-fold in a Ca2+-dependent manner, and the rate of fusion approached 25% of that seen in wild-type synapses under the same conditions. Similarly, the mESC frequency in n-syb null mutants could be increased by a Ca2+ ionophore, A23187, and by black widow spider venom. Thus, the ability of the vesicles to fuse in response to sustained increases in cytosolic Ca2+ persisted in the absence of this protein. Tetanic stimulation could also increase the frequency of mESCs, particularly toward the end of a train and after the train of stimuli. In contrast, these mutants did not respond to an elevation of cAMP induced by an activator of adenylyl cyclase, forskolin, or a membrane-permeable analog of cAMP, dibutyryl cAMP, which in wild-type synapses causes a marked increase in the mESC frequency even in the absence of external Ca2+. These results are discussed in the context of models that invoke a special role for n-syb in coupling fusion to the transient, local changes in Ca2+ and an as yet unidentified target of cAMP.

Cadmium↗
PubMed1996

Temporally manipulated rescue of visual and courtship abnormalities caused by a nonA mutation in Drosophila.

The no-on-transient-A gene was identified by independently isolated mutations causing visual-response abnormalities or courtship song defects. The nonA(diss) mutant is abnormal for all of these phenotypes. The pleiotropic effects of this dissonance allele dovetail with the widespread tissue expression of the nonA products. This gene, which encodes a putative RNA-binding protein, is expressed at essentially all stages of the life cycle. To determine whether the behavioral and physiological abnormalities exhibited by nonA mutant adults have a developmental etiology or are the result of an impaired mature nervous (or perhaps neuro-muscular) system, a conditional form of this gene was constructed. Animals from the resulting hsp-nonA (cDNA) transgenic strain were subjected to heat-shock regimes such that the gene's coding sequences were activated during development only, solely in the imaginal stage, or both. Surprisingly, expression during any of these time periods effected rescue of the visual-response and the courtship-song defects.

Animals↗