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61.
The Xenopus borealis somatic 5S ribosomal RNA gene was used as a model system to determine the mutual effects of nucleosome folding and formation of ultraviolet (UV) photoproducts (primarily cis-syn cyclobutane pyrimidine dimers, or CPDs) in chromatin. We analyzed the preferred rotational and translational settings of 5S rDNA on the histone octamer surface after induction of up to 0.8 CPD/nucleosome core (2.5 kJ/m(2) UV dose). DNase I and hydroxyl radical footprints indicate that UV damage at these levels does not affect the average rotational setting of the 5S rDNA molecules. Moreover, a combination of nuclease trimming and restriction enzyme digestion indicates the preferred translational positions of the histone octamer are not affected by this level of UV damage. We also did not observe differences in the UV damage patterns of irradiated 5S rDNA before or after nucleosome formation, indicating there is little difference in the inhibition of nucleosome folding by specific CPD sites in the 5S rRNA gene. Conversely, nucleosome folding significantly restricts CPD formation at all sites in the three helical turns of the nontranscribed strand located in the dyad axis region of the nucleosome, where DNA is bound exclusively by the histone H3-H4 tetramer. Finally, modulation of the CPD distribution in a 14 nt long pyrimidine tract correlates with its rotational setting on the histone surface, when the strong sequence bias for CPD formation in this tract is minimized by normalization. These results help establish the mutual roles of histone binding and UV photoproducts on their formation in chromatin. 相似文献
62.
Spectrometric studies on stability of tenuazonic acid (TeA) solution in organic solvents 总被引:1,自引:0,他引:1
The stability of tenuazonic acid solution at different temperatures and storage times was studied using methanol, methanol-water
(8:2 v/v), benzene and benzene-acetonitrile (98:2 v/v) as solvents. Solutions were analysed by a spectrometric method TeA
U.V.-spectrum was recorded. Results indicated that the optimum temperature for long-time storage period of tenuazonic acid
solution in any solvent assayed is -20°C. Benzene and benzene-acetonitrile (98:2 v/v) could be advised to make tenuazonic
acid solution which will be stored less than 2 months at 4°C. Methanol and methanolwater (8:2 v/v) are not recommended because
a low stability of TeA solution in this solvents. 相似文献
63.
Control of phenylalanyl-tRNA synthetase genetic expression. Site-directed mutagenesis of the pheS, T operon regulatory region in vitro 总被引:1,自引:0,他引:1
J F Mayaux G Fayat M Panvert M Springer M Grunberg-Manago S Blanquet 《Journal of molecular biology》1985,184(1):31-44
Previous studies of phenylalanyl-tRNA synthetase expression in Escherichia coli strongly suggested that the pheS, T operon was regulated by a phenylalanine-mediated attenuation mechanism. To investigate the functions of the different segments composing the pheS, T attenuator site, a series of insertion, deletion and point mutations in the pheS, T leader region have been constructed in vitro on a recombinant M13 phage. The effects of these alterations on the regulation of the operon were measured after transferring each mutation onto a lambda phage carrying a pheS, T-lacZ fusion. The behaviours of the various mutants agree with the predictions of the attenuation model. The role of the antiterminator (2-3 pairing) as competitor of the terminator (3-4 pairing) is demonstrated by several mutations affecting the stability of the 2-3 base-pairing. The existence of deletions and point mutations in the 3-4 base-pairing shows that the terminator is essential for both expression level and regulation of the operon. Mutations in the translation initiation site of the leader peptide show that the expression of the leader peptide is essential for attenuation control. However, alteration of the translation initiation rate of the leader peptide derepresses the pheS, T operon, which is the opposite of what is observed with the trp operon. This difference is explained in terms of different translation initiation efficiencies of the leader peptides. Finally, insertion mutations, increasing gradually the distance between the leader peptide stop codon and the first strand of the antiterminator, derepress the pheS, T operon and show that formation of the antiterminator structure is under the control of the translation of the leader peptide. 相似文献
64.
Screening for five mutations detects 97% of cystic fibrosis (CF) chromosomes and predicts a carrier frequency of 1:29 in the Jewish Ashkenazi population. 下载免费PDF全文
D Abeliovich I P Lavon I Lerer T Cohen C Springer A Avital G R Cutting 《American journal of human genetics》1992,51(5):951-956
To determine the distribution and frequency of cystic fibrosis (CF) mutations in the Israeli population, we have screened 96 patients for 11 relatively common mutations. Five mutations--delta F508, G542X, W1282X, N1303K, and 3849 + 10kb C-->T--were found to account for 97% of the CF alleles in the Ashkenazi Jews. In contrast, of the 11 mutations tested, only delta F508 was detected in Jewish patients of Sephardic or Oriental origin, accounting for 43% of the CF alleles. Four mutations--delta F508, G542X, W1282X, and N1303K--accounted for 55% of the CF alleles in Arab patients. In a pilot screening study, a random sample of 424 Ashkenazi individuals was analyzed for three mutations--delta F508, W1282X, and G542X. Thirteen individuals were detected as heterozygotes (six for delta F508 and seven for W1282X), predicting a heterozygote frequency of 1:29. This is similar to the frequency of carriers in the Caucasian population of northern European ancestry. On the basis of these data, the Ashkenazi population is considered to be a candidate for CF heterozygote screening. 相似文献
65.
Boland JL Corbeij HA Van Der Giessen W Seabra-Gomes R Suryapranata H Wijns W Hanet C Suttorp MJ Buller C Bonnier JJ Colombo A Van Birgelen C Pieper M Mangioni JA Londero H Carere RG Hamm CW Bonan R Bartorelli A Kyriakides ZS Chauhan A Rothman M Grinfeld L Oosterwijk C Serruys PW Cumberland DC 《International journal of cardiovascular interventions》2000,3(4):215-225
AIMS: The BiodivYsio trade mark stent (Biocompatibles Ltd, Farnham, UK) is coated with a phosphorylcholine (PC)-containing copolymer to confer biocompatibility. The SOPHOS (Study Of PHosphorylcholine coating On Stents) study was designed to assess the safety and efficacy of this novel coronary stent and by indirect comparison to indicate equivalence with other formal stent studies. METHODS AND RESULTS: Patients with angina and a single short (#x2A7F;12 mm) de novo lesion in a native coronary artery of >/=2.75 mm diameter were included. A total of 425 patients were allocated in 24 centers. Clinical data were collected at one-, six- and nine-month follow-up. Angiography was performed before and after the stent implantation. In addition, in the first 200 patients (SOPHOS A) angiography was routinely performed at six months. The following 225 patients (SOPHOS B) were merely followed up clinically. The primary end-point of the study, the six-month MACE-rate (MACE = Major Adverse Cardiac Events) was 13.4% (two cardiac death; five Q-wave/nine non-Q-wave myocardial infarctions (MI); nine CABG and 32 target lesion revascularization (TLR), which is similar to the calculated 15% MACE-rate in comparable reference studies. Secondary end-points included among others restenosis at six months in the SOPHOS A population. The target vessel diameter was 2.98 +/- 0.48 mm. Minimal lumen diameter pre/post procedure and at follow-up was 1.00 +/- 0.32, 2.69 +/- 0.37, 1.91 +/- 0.71 mm, respectively. The binary restenosis rate (>/=50% diameter stenosis at follow-up) was 17.7%. CONCLUSION: The coronary BiodivYsio stent is safe and effective as a primary device for the treatment of native coronary artery lesions in patients with stable or unstable angina pectoris. Clinical and angiographic results are in the statistical range of equivalence with comparable studies with other current stents. 相似文献
66.
Trans-splicing is an unusual process in which two separate RNA strands are spliced together to yield a mature mRNA. We present a novel computational approach which has an overall accuracy of 82% and can predict 92% of known trans-splicing sites. We have applied our method to chromosomes 1 and 3 of Leishmania major, with high-confidence predictions for 85% and 88% of annotated genes respectively. We suggest some extensions of our method to other systems. 相似文献
67.
This investigation examined the exposure of Egyptian infants to Aflatoxin M1 (AfM1) and of lactating mothers to Aflatoxin B1, using AfM1 in human milk as a biomarker for exposure to AfB1. The presence of ochratoxin A (OA) in human milk was also investigated to determine the levels of infants exposure to OA
from human milk. The results indicated that AfM1 was found in 66 (55 %) of 120 human milk samples with a mean of 0.3 ± 0.53 ng/mL (range 0.02 to 2.09 ng/mL). OA was found
in 43 (35.8 %) of 120 human milk samples with a mean of 21.1 ± 13.7 ng/mL (range 5.07 to 45.01 ng/mL), which will cause a
daily intake of OA from human milk exceeding the suggested tolerable dose of 5 ng/kg-1 of OA body weight. On the other side AfM1 was found in 25 % of blood samples (5 out of 20 samples), at a mean of 1.18 ng/mL, but it was detected only in one urine
sample (1 out of 20 samples). OA was detected only in 2 out of 13 blood samples (15.4 %) with an average 3.67 ng/mL. Whereas
OA was not detected in all analyzed urine samples. 相似文献
68.
Jossi Hillel Martien AM Groenen Michèle Tixier-Boichard Abraham B Korol Lior David Valery M Kirzhner Terry Burke Asili Barre-Dirie Richard PMA Crooijmans Kari Elo Marcus W Feldman Paul J Freidlin Asko M?ki-Tanila Marian Oortwijn Pippa Thomson Alain Vignal Klaus Wimmers Steffen Weigend 《遗传、选种与进化》2003,35(6):533-557
In a project on the biodiversity of chickens funded by the European Commission (EC), eight laboratories collaborated to assess the genetic variation within and between 52 populations from a wide range of chicken types. Twenty-two di-nucleotide microsatellite markers were used to genotype DNA pools of 50 birds from each population. The polymorphism measures for the average, the least polymorphic population (inbred C line) and the most polymorphic population (Gallus gallus spadiceus) were, respectively, as follows: number of alleles per locus, per population: 3.5, 1.3 and 5.2; average gene diversity across markers: 0.47, 0.05 and 0.64; and proportion of polymorphic markers: 0.91, 0.25 and 1.0. These were in good agreement with the breeding history of the populations. For instance, unselected populations were found to be more polymorphic than selected breeds such as layers. Thus DNA pools are effective in the preliminary assessment of genetic variation of populations and markers. Mean genetic distance indicates the extent to which a given population shares its genetic diversity with that of the whole tested gene pool and is a useful criterion for conservation of diversity. The distribution of population-specific (private) alleles and the amount of genetic variation shared among populations supports the hypothesis that the red jungle fowl is the main progenitor of the domesticated chicken. 相似文献
69.
In many species of bacteria most inducible DNA repair genes are regulated by LexA homologues and are dependent on RecA for induction. We have shown previously by analysing the induction of recA that two mechanisms for the induction of gene expression following DNA damage exist in Mycobacterium tuberculosis. Whereas one of these depends on RecA and LexA in the classical way, the other mechanism is independent of both of these proteins and induction occurs in the absence of RecA. Here we investigate the generality of each of these mechanisms by analysing the global response to DNA damage in both wild-type M. tuberculosis and a recA deletion strain of M. tuberculosis using microarrays. This revealed that the majority of the genes that were induced remained inducible in the recA mutant stain. Of particular note most of the inducible genes with known or predicted functions in DNA repair did not depend on recA for induction. Amongst these are genes involved in nucleotide excision repair, base excision repair, damage reversal and recombination. Thus, it appears that this novel mechanism of gene regulation is important for DNA repair in M. tuberculosis. 相似文献
70.
Jens O. Watzlawik Xu Hou Dominika Fricova Chloe Ramnarine Sandeep K. Barodia Tania F. Gendron Michael G. Heckman Michael DeTure Joanna Siuda Zbigniew K. Wszolek Clemens R. Scherzer Owen A. Ross Guojun Bu Dennis W. Dickson Matthew S. Goldberg Fabienne C. Fiesel Wolfdieter Springer 《Autophagy》2021,17(9):2613