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At least 199 records · Page 11Linked to original sources
PubMed2001

Flies, clocks and evolution.

The negative feedback model for gene regulation of the circadian mechanism is described for the fruitfly, Drosophila melanogaster. The conservation of function of clock molecules is illustrated by comparison with the mammalian circadian system, and the apparent swapping of roles between various canonical clock gene components is highlighted. The role of clock gene duplications and divergence of function is introduced via the timeless gene. The impressive similarities in clock gene regulation between flies and mammals could suggest that variation between more closely related species within insects might be minimal. However, this is not borne out because the expression of clock molecules in the brain of the giant silk moth, Antheraea pernyi, is not easy to reconcile with the negative feedback roles of the period and timeless genes. Variation in clock gene sequences between and within fly species is examined and the role of co-evolution between and within clock molecules is described, particularly with reference to adaptive functions of the circadian phenotype.

Adaptation, Physiological↗
PubMed2000

A segmental gene duplication generated differentially expressed myb-homologous genes in maize.

The myb-homologous p1 gene regulates the synthesis of flavonoid pigments in maize kernel pericarp and cob; these floral organs are greatly modified in size and shape compared with their counterparts in teosinte, the progenitor of maize. To elucidate the molecular evolution of the p1 gene in relation to its expression and possible functions in maize and teosinte, we have isolated a second maize gene (p2) that is highly homologous with the p1 gene, and a related gene (p2-t) from Zea mays subsp parviglumis. We present evidence that the maize p1 and p2 genes were generated by duplication of an ancestral p gene (p(pre)) and its downstream sequences; the duplicated 3' flanking sequences were inserted upstream of the p(pre) gene, thereby changing its transcription pattern. This model accounts for the structural organization and the observed differential expression of the p1 and p2 genes: p1 transcripts accumulate in kernel pericarp, cob, tassel glumes, and silk, whereas p2 transcripts are found in developing anther and silk. The duplication is estimated to have occurred 2.75 million years ago; subsequently, multiple retroelements have been inserted between the p1 and p2 genes. Our results demonstrate the evolution of a single gene into a compound locus containing two component genes with different tissue specificities. Expression of the p1 gene in the kernel pericarp may have provided a selective advantage during the evolution of maize kernel morphology.

Amino Acid Sequence↗
PubMed1997

TLP1: a gene encoding a protein component of mammalian telomerase is a novel member of WD repeats family.

We have cloned and characterized the rat telomerase protein component 1 gene (TLP1), which is related to the gene for Tetrahymena p80. The cDNA encodes a 2629 amino acid sequence and produces the TLP1 proteins p240 and p230. The anti-TLP1 antibody specifically immunoprecipitated the telomerase activity. Moreover, p240 and p230 were copurified with telomerase activity in a series of extensive purification experiments. These results strongly suggest that the TLP1 proteins are components of, or are closely associated with, the rat telomerase. A pulse-chase experiment showed that p240 is modified to p230 in vivo. p230 was the dominant form in telomerase-positive cells, suggesting that modification of the TLP1 protein may regulate telomerase activity in vivo.

Animals↗
PubMed2001

Identification and analyses of the Xenopus TERT gene that encodes the catalytic subunit of telomerase.

The Xenopus telomerase catalytic component gene, xTERT (Xenopus telomerase reverse transcriptase), has been cloned. The production of xTERT recombinant protein together with the proposed Xenopus telomerase RNA (xTR) (Chen et al., 2000. Cell 100, 503-514) in a rabbit reticulocyte lysate system led to the reconstitution of active telomerase, indicating that both products are functional telomerase components. Both xTERT expression and telomerase activity are high from the early to the late blastula stage. However, they are decreased at the gastrula stage and thereafter, suggesting that the xTERT expression level is the primary mechanism for regulating telomerase activity in Xenopus development. This is the first report of a non-mammalian vertebrate TERT gene. Sequence comparison of xTERT with human and mouse TERTs has uncovered four regions conserved in the amino-terminal halves of vertebrate TERT proteins, the functions of which will be discussed herein.

Amino Acid Sequence↗
PubMed1998

Chromosomal locations of three human nuclear genes (RPSM12, TUFM, and AFG3L1) specifying putative components of the mitochondrial gene expression apparatus.

We have mapped the chromosomal locations of three human nuclear genes for putative components of the apparatus of mitochondrial gene expression, using a combination of in situ hybridization and interspecies hybrid mapping. The genes RPMS12 (mitoribosomal protein S12, a conserved protein component of the mitoribosomal accuracy center), TUFM (mitochondrial elongation factor EF-Tu), and AFG3L1 (similar to the yeast genes Afg3 and Rca1 involved in the turnover of mistranslated or misfolded mtDNA-encoded polypeptides) were initially characterized by a combination of database sequence analysis, PCR, cloning, and DNA sequencing. RPMS12 maps to chromosome 19q13.1, close to the previously mapped gene for autosomal dominant hearing loss DFNA4. The TUFM gene is located on chromosome 16p11.2, with a putative pseudogene or variant (TUFML) located very close to the centromere of chromosome 17. AFG3L1 is located on chromosome 16q24, very close to the telomere. By virtue of their inferred functions in mitochondria, these genes should be regarded as candidates of disorders sharing features with mitochondrial disease syndromes, such as sensorineural deafness, diabetes, and retinopathy.

ATPases Associated with Diverse Cellular Activitie↗
PubMed2006

Quantitative detection of gene expression and toxin complex produced by Clostridium botulinum serotype D strain 4947.

Botulinum toxin is produced by Clostridium botulinum as a large toxin complex (L-TC) non-covalently assembled with a neurotoxin (NT), a non-toxic non-hemagglutinin (NTNHA) and hemagglutinin subcomponents (HA-70, HA-33, and HA-17). In this study, the gene expressions of five individual L-TC components were examined by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in C. botulinum serotype D strain 4947 (D-4947) during cell growth. Transcripts for the five component genes were successfully detected in the mid-exponential growth phase (6.5 h), reaching a maximum at the early stationary growth phase (12 h). The ratio of the mRNA transcripts of nt and ntnha was approximately 1:1, suggesting that nt and ntnha are bicistronically transcribed. On the other hand, the transcript levels of the ha genes were several-fold higher than those of nt and ntnha, although the mRNA transcript level of ha-33 was less than the other two ha subcomponent genes. The results based on qRT-PCR indicate that a shortage of HA-33 among the proteins associated with botulinum TC could explain the production by D-4947 of other smaller-sized L-TCs (610, 540 and 410 kDa) with fewer HA-33 molecules than the mature 650 kDa L-TC. Western blot analysis demonstrated that TC species in cell lysate were initially observed in the mid-exponential phase, while extracellular TCs were detected subsequently in the early stationary phase.

Bacterial Proteins↗
PubMed2003

Chromosomal imbalances in primary and metastatic melanomas: over-representation of essential telomerase genes.

Comparative genomic hybridization was used to map copy number abnormalities in 48 short-term cell cultures established from different stages and types of human melanoma. A variety of random and non-random chromosomal alterations were detected, with gains within chromosomes 20q, 7q, 7p, 20p, 6p and 17q and losses in 9p, 10q, 6q, 10p, 4q, and 11q being the most common observations. In addition, several other chromosomal loci were over- or under-represented in subgroups of melanomas. For example, sequences on 3q26 were over-represented in 33% and on 5p15.33 in 27% of cell cultures, reaching the level of amplification in 12% and 22%, respectively. These regions harbour the two essential genes for the enzyme telomerase: the telomerase reverse transcriptase gene (hTERT) on 5p15.33 and the telomerase RNA component gene (hTERC) on 3q26. Using fluorescence in situ hybridization and Southern blot analysis, both genes were shown to be over-represented or amplified in several melanomas. Interestingly, hTERT amplification was abundant in superficial spreading primary melanomas, subcutaneous metastases and malignant effusion-derived cells, but completely absent or very rare in primary nodular melanomas as well as brain, bone and lymph node metastases. Several chromosomes or chromosomal regions harbouring telomerase-suppressing activities (3p, 4, 6 and 10p) were frequently under-represented in melanomas. Our data suggest that genetic alterations at several chromosomal loci might facilitate activation of telomerase during the development of cutaneous malignant melanoma.

Adult↗
PubMed1989

Tissue kallikreins and kinins: regulation and roles in hypertensive and diabetic diseases.

The spectrum of cellular, or whole animal responses to kinins has expanded enormously in the last five years. The molecular basis for these consequences of kinin-kinin receptor interactions is being glimpsed as a series of cascading and parallel biochemical events occurring either in the same or adjacent, but communicating, cells of the same tissue (e.g. epithelial, endothelial, muscle, neural). Although it is likely that even more kinin-induced events remain to be discovered, like the interesting effects of the peptides on osteoclastic activity (128), a greater challenge in this field is the gathering of insights into precisely how the regulation of system component gene expression is coordinately carried out to allow component protein synthesis, transport and processing when necessary, and limitation of activities, when required. With these insights, we will be more able to understand the meaning of many observations of tissue kallikrein-kinin system abnormalities in common human diseases. This understanding will then make more obvious the drug design strategies to be used to stimulate or replace, and modulate or inhibit kallikrein-kinin system components in those diseases.

Animals↗
PubMed1995

Transcriptional regulation of the junB promoter: analysis of STAT-mediated signal transduction.

The product of the junB gene is a member of the AP-1 family of transcription factors that activate transcription by binding to TPA-responsive elements (TREs) within the promoters of target genes. Components of AP-1 are immediate-early genes whose expression is upregulated by a plethora of extracellular stimuli and are important in mediating cellular proliferation and differentiation. Such stimuli include the pleiotropic cytokine interleukin-6 (IL-6) which plays a role in immune and inflammatory responses and ciliary neurotrophic factor (CNTF) which enhances survival and differentiation of neurons and glia. We have analysed expression from junB promoter-CAT reporter constructs in HepG2 cells and found that a region between -196 and -91 can mediate response to IL-6 and CNTF and was able to confer responsiveness to a heterologous promoter. We further show by gel retardation analysis that distinct nuclear factors induced by IL-6 specifically bind to this interleukin-6 response element (IRE). This region contains both a putative ETS- and a STAT-transcription factor binding site. We show by mutational analysis and supershift data that the IL-6 induced complex indeed contains the transcription factor APRF/Stat3 that is both necessary and sufficient for activation. Interestingly this site does not appear to bind Stat1 itself, as shown by supershift analysis and a lack of response to IFN-gamma both at the DNA-binding and transcriptional level. Furthermore, we demonstrate that the junB IRE-binding activity induced by IL-6 requires tyrosine kinase activity, whereas induced transactivation of IRE-constructs additionally occurs through an H7-sensitive pathway that is p21ras-independent, implicating serine/threonine kinases in the transactivation of IRE-binding factors.

Animals↗
PubMed1997

Activated and inactivated renin-angiotensin system in transgenic animals: from genes to blood pressure.

Much of our knowledge about blood pressure regulation has come from a huge number of biochemical, endocrinologic, pharmacologic, clinical, and physiologic studies. The renin-angiotensin system, composed of enzymatic and signal-transduction cascades, has a key role in regulating arterial blood pressure and in developing certain forms of experimentally induced hypertension and hypertension in human beings. Angiotensin peptides, the products of this system, exert a wide range of physiologically important effects on many tissues, including those of the cardiovascular system, through their actions on angiotensin receptors. Recently, several groups have succeeded in generating animals transgenic for the renin or angiotensinogen genes, or with a targeted disruption of the component genes of the renin-angiotensin system. This brief review describes advances of the in vivo analysis of blood pressure regulation by focusing on the renin-angiotensin system.

Amino Acid Sequence↗
PubMedDate not supplied

[Discrimination between genetic factors in attention deficit].

INTRODUCTION AND OBJECTIVE: In order to elucidate the genetic and environmental components involved in the susceptibility to develop attention deficit hyperactivity disorder (ADHD), a complex segregation analysis on nuclear families (n = 53) ascertained from affected probands belonging to Medellín, in the Antioquian State, Colombia, was performed. METHODS AND RESULTS: Models of cohort effect (non-inheritance), multifactorial, recessive major gene, non-major gene component and non-transmission of major gene were rejected. Contrarily, dominant and codominant major gene models and non-multifactorial component could not be rejected. Thus, the better model fitting the data was that of the major gene (dominant/codominant). This major gene explains more than 99.99% of the ADHD phenotypic variance (value of heritability in the mixed model equal to 0.007%), which permit to assume a low aport of the environmental component to the phenotype ADHD. Gene frequency of the major gene was 3% in the general population of Antioquia and its penetrance was closed to 30%. CONCLUSION: Some cautions and aspects related to the bias of the interview and diagnosis of the parents are discussed.

Attention Deficit Disorder with Hyperactivity↗
PubMed2007

Common genetic variations in CCK, leptin, and leptin receptor genes are associated with specific human eating patterns.

Obesity has a heritable component; however, the heterogeneity of obesity complicates dissection of its genetic background. In this study, we therefore focused on eating patterns as specific traits within obesity. These traits have a heritable component; genes associated with a specific eating pattern have not yet been reported at the population level. In this study, we determined whether genetic variations in cholecystokinin (CCK) and leptin genes underlie specific eating patterns. We selected obese individuals showing extreme snacking behavior or use of excessive portion sizes from a large population-based sample (n = 17,357) from the Prospect-EPIC (European Prospective Study into Cancer and Nutrition) study. Using allele-specific PCRs, we tested several single nucleotide polymorphisms in the candidate genes and performed haplotype analysis. Obese carriers of common allelic variations in leptin or the leptin receptor gene had an increased risk to display extreme snacking behavior. In contrast, obese carriers of common allelic variations in CCK had an increased risk to eating increased meal sizes. In conclusion, we identified common allelic variants specifically associated with distinctly different eating patterns, namely extreme snacking behavior or excessive portion size.

Aged↗
PubMed1996

Organization and nucleotide sequence of genes for hemagglutinin components of Clostridium botulinum type B progenitor toxin.

The genes for hemagglutinin components (33 kD, 17 kD, and 21.5 kD) of Clostridium botulinum type B progenitor toxin were cloned and sequenced. Analysis of the nucleotide sequence showed that the 33 kD, 17 kD, and 21.5 kD hemagglutinin genes were organized into an operon in the 5'upstream region of the toxin gene and their ORF orientation were opposite to that of the toxin gene. A comparison of amino acid sequences between the hemagglutinin components in type B and type C progenitor toxin showed significant homology. Northern blot analysis also revealed that all of the genes for the hemagglutinin components were transcribed as a polycistronic RNA.

Amino Acid Sequence↗
PubMed1991

Mitochondrial genome of Saccharomyces douglasii: genes coding for components of the protein synthetic apparatus.

Mitochondrial genes coding for some components of the protein synthetic apparatus in S. douglasii have been studies in detail. A region containing stretches of high homology to the S. cerevisiae tRNA synthesis locus (TSL) and the tRNA(fmet) gene has been identified and sequenced. The organization of this region was very similar to that present in S. cerevisiae, including the presence of a possible transcription starting signal. The S. douglasii TSL gene is shorter due to several deletions which, however, do not involve the regions coding for RNA domains know to be required for the catalytic activity of mitochondrial RNAse P. The S. douglasii LSU rRNA gene has been shown to contain a typical group I intron highly homologous to its S. cerevisiae counterpart, except for the absence of the open reading frame which in S. cerevisiae codes for I-SceI endonuclease.

Base Sequence↗
PubMed1989

Robustness of the unified model to shared environmental effects in the analysis of dichotomous traits.

Simulation studies were conducted to assess to what extent the conclusions of segregation analysis, performed under the unified model, can be affected by the presence of unmeasured environmental factors shared by family members. Dichotomous data were generated on six-member nuclear families under two variants of the mixed model, incorporating environmental effects shared by all family members. When the generating model includes a polygenic component and a shared environmental effect, there is false detection of a major gene, especially when the joint likelihood of parents' and offspring's phenotypes is computed. The proportion of false conclusions increases as the shared environmental effect increases. On the other hand, the presence of a shared environmental effect in addition to a major gene component does not alter the detection of the major gene nor the transmission probability estimates, which are close to the expected Mendelian values. The rejection of the Mendelian transmission hypothesis, as observed in familial analyses of affected disorders, might be the result of mechanisms other than those considered here, such as more complex sources of environmental resemblance or a possible genetic heterogeneity.

Affective Disorders, Psychotic↗
PubMed1993

Genetic models of human obesity--family studies.

Childhood obesity is predictive of obesity as an adult, and individual differences in body weight relative to height (body mass index) in adults are important predictors of morbidity as well as mortality from atherosclerotic cardiovascular disease. The observation of strong familial correlations does not ensure that genes are involved in the determination of body mass index, because individuals in families share environments as well as genes. However, several recent studies have found evidence for both additive (polygene) and nonadditive (major gene) components. A question that results from these analyses is--what gene(s) has been inherited that carries an associated risk, most likely mediated by environmental exposures, for obesity? Studies to identify genetic loci linked to familial obesity should add to our understanding of the genetic factors involved in the determination of obesity and may lead to early identification of individuals and families at high risk for the chronic disorders that are associated with obesity.

Body Mass Index↗
PubMed1992

Transactivation of geminivirus AR1 and BR1 gene expression by the viral AL2 gene product occurs at the level of transcription.

Tomato golden mosaic virus is a bipartite geminivirus whose genome is divided between two circular DNA molecules. DNA A encodes functions necessary for viral DNA replication and encapsidation, whereas DNA B provides functions needed for movement in the host. Previous studies have shown that the viral AL2 gene product transactivates expression of the coat protein gene (AR1). We have investigated the role of the AL2 protein in the regulation of B component gene expression and examined the transcriptional and post-transcriptional components of this regulation. We found that AL2 protein is required for efficient expression of both the AR1 and BR1 genes, but not the BL1 gene. A comparison of steady state transcript levels and transcript levels determined by nuclear run-on analysis showed that activation of AR1 and BR1 gene expression by the AL2 protein occurs primarily at the level of transcription. These results provide an explanation for the lack of infectivity demonstrated by AL2 mutants, and suggest that the AL2 protein interacts with the cellular transcription machinery to activate the expression of rightward viral genes.

Amino Acid Sequence↗
PubMed2002

Pathogenic potential of fifty Bacillus weihenstephanensis strains.

The aim of this study was to evaluate the food poisoning potential of strains of the new species in the Bacillus cereus group, B. weihenstephanensis. Fifty strains were tested for cytotoxicity in a Vero cell assay, and 23 of the strains were also tested for production of enterotoxin components with commercial antibody kits, and for presence of enterotoxin gene components by polymerase chain reaction (PCR). The majority of the strains (72%) were not cytotoxic, although all of the strains that were tested with PCR and commercial kits had part of at least one of the B. cereus enterotoxins Hbl, Nhe or CytK.

Animals↗