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41.
This paper presents the first example of a complete gene sequence coding for and expressing a biologically functional human tRNA methyltransferase: the hTRM1 gene product tRNA(m22G)dimethyltransferase. We isolated a human cDNA (1980 bp) made from placental mRNA coding for the full-length (659 amino acids) human TRM1 polypeptide. The sequence was fairly similar to Saccharomyces cerevisiae Trm1p, to Caenorhabditis elegans TRM1p and to open reading frames (ORFs) found in mouse and a plant (Arabidopsis thaliana) DNA. The human TRM1 gene was expressed at low temperature in Escherichia coli as a functional recombinant protein, able to catalyze the formation of dimethylguanosine in E.coli tRNA in vivo. It targeted solely position G26 in T7 transcribed spliced and unspliced human tRNATyr in vitro and in yeast trm1 mutant tRNA. Thus, the human TRM1 protein is a tRNA(m22G26)dimethyltransferase. Compared with yeast Trm1p, hTRM1p has a C-terminal protrusion of ~90 amino acids which shows similarities to a mouse protein related to RNA splicing. A deletion of these 90 C-terminal amino acids left the modification activity in vitro intact. Among point mutations in the hTRM1 gene, only those located in conserved regions of hTRM1p completely eliminated modification activity. 相似文献
42.
Transfer ribonucleic acid (tRNA) that is deficient in methyl groups may be detected in logarithmically growing Saccharomyces cerevisiae. The amount of methyl-deficient tRNA is not constant throughout the logarithmic phase, but is maximal about one generation before the onset of the late growth phase. During this latter phase, the tRNA is fully methylated. The methyl-deficient tRNA is present during a period of high metabolic activity of the cell, characterized by increased RNA and protein content. 相似文献
43.
CHARGE CONTRAST IMAGING OF EXCEPTIONALLY-PRESERVED FOSSILS 总被引:1,自引:0,他引:1
Abstract: Charge contrast images are a variant of secondary electron images acquired by operating a variable pressure scanning electron microscope in low vacuum mode; i.e. a gas is present in the specimen chamber. Spatial variation in the amount of charge that accumulates on the surface of the specimen is expressed as differences in greyscale tone; areas that are charging less are darker in tone. The precise mechanisms by which charge contrast images are generated are not known fully. Various different properties of a mineral may create a charge contrast; electrical conductivity is known to be one potentially important variable. As carbon is highly conductive but typical host lithologies (carbonates, silicates) less so or dielectric, the technique is potentially very suitable for imaging organically preserved fossils such as those from the Solite and Jehol biotas. It can also be applied to Burgess Shale fossils: complex films comprising 'aluminosilicates' with or without carbonaceous remains. Charge contrast images reveal anatomical detail not visible using either optical or other scanning electron microscope-based imaging methods. 相似文献
44.
Sponsored by Waters Corporation organized by the Education Committee: Dr. Kevin L. Knudtson Dr. Allis S. Chien Dr Natalia G. Reyero Vinas Dr LeRoy Martin Dr. Janet M Murray Dr. Paul A Rudnick Brian C. Searle Michael Zianni Tim C Hunter James Van Ee David Needleman Elke Kuster-Schock 《Journal of biomolecular techniques》2013,24(2):112
45.
GIOVANNA MASSEI JULIA COATS ROGER QUY KATE STORER DAVE P. COWAN 《The Journal of wildlife management》2010,74(2):333-336
ABSTRACT Bait-delivered pharmaceuticals, increasingly used to manage populations of wild boar (Sus scrofa) and feral pigs, may be ingested by nontarget species. Species-specificity could be achieved through a delivery system. We designed the BOSTM (Boar-Operated-System) as a device to deliver baits to wild pigs. The BOSTM consists of a metal pole onto which a round perforated base is attached. A metal cone with a wide rim slides up and down the pole and fully encloses the base onto which the baits are placed. We conducted a pilot, captive trial and found that captive wild boar fed from the BOSTM either directly, by lifting the cone, or indirectly, by feeding once another animal had lifted the cone. Thus, we tested whether free-living wild boar fed from the BOSTM and whether the BOSTM could prevent bait uptake by nontarget species. We observed that free-living wild boar fed regularly from the BOSTM and that the device successfully prevented bait uptake by nontarget species. The BOSTM should be trialed more extensively to confirm its effectiveness and species-specificity to distribute pharmaceuticals to wild suids. If successful, the BOSTM could be used to deliver vaccines in disease control programs as well as contraceptives to manage overabundant populations of wild suids. 相似文献
46.
17-Hydroxyprogesterone is a well-known precursor of androstenedione in adrenal biosynthesis. This study using sheep adrenal incubations demonstrates that 11-deoxycortisol, the precursor of cortisol synthesis, also can be a precursor of androstenedione. Indeed, our data show that androstenedione synthesis is negatively correlated to the synthesis of cortisol and cortisone. This fact allowed us to infer that this new pathway is closely related to the activity of the 11 beta-hydroxylase that is responsible for the synthesis of cortisol. Indeed, when the activity of this enzyme is impaired, 11-deoxycortisol follows the pathway that leads to androstenedione synthesis in the adrenals. This pathway could explain, at least in part, the marked increase of androstenedione observed in congenital adrenal hyperplasia due to 11 beta-hydroxylase deficiency. 相似文献
47.
48.
The phi 80 and P22 attachment sites. Primary structure and interaction with Escherichia coli integration host factor 总被引:51,自引:0,他引:51
J M Leong S Nunes-Düby C F Lesser P Youderian M M Susskind A Landy 《The Journal of biological chemistry》1985,260(7):4468-4477
Although the lambdoid bacteriophage phi 80 and P22 possess site-specific recombination systems analogous to bacteriophage lambda, they have different attachment (att) site specificities. We have identified and determined the nucleotide sequences of the att sites of phi 80 and P22 and have examined the interaction of these sites with purified Escherichia coli integration host factor (IHF). The sizes of the homologous core regions of the att sites vary greatly: P22 has a 46-base pair core, while phi 80 and lambda have 17- and 15-base pair cores, respectively. The core sequences of the three phage show no significant homology, although dispersed regions of homology in arm sequences indicate that the three phage att sites are related. All three att sites have a high A + T composition, and restriction fragments carrying these sites migrate anomalously upon polyacrylamide gel electrophoresis. IHF binds to a site to the left of the common core in the phi 80 and P22 phage att sites (attP) and to a site to the right of the core in P22 attP and attB (the bacterial att site). In the lambda system, IHF interacts with three regions on attP (designated H1, H2, and H') and none on attB (Craig N., and Nash, H.A. (1984) Cell 39, 707-716). Alignment of the IHF sites of all three phage results in a consensus sequence for IHF binding, Pyr-AANNNNTTGATAT. Among the three phage, the number of IHF sites differs; however, the location and orientation of the binding sites in relation to the respective core regions are well conserved. An IHF site analogous to lambda H2 is present in both phi 80 and P22 attP, while a site analogous to lambda H' is present in P22 attP. This conservation suggests that IHF plays a very similar role in the site-specific recombination pathways of all three phage, and that the flanking arm sequences are necessary for phi 80 and P22 attP function, as is the case for lambda attP function. These structural similarities presumably reflect a conservation of the mechanism of site-specific recombination for the three phage. 相似文献
49.
50.
通过RNA印迹分析和亚硝酸盐含量测定检查TNF-α、IL-1β和LPS对大鼠血管平滑肌细胞(VSMC)诱导型一氧化氮合酶(iNOS)基因表达及NO生成的影响.结果表明,TNF-α、IL-1β和LPS均能显著诱导VSMCiNOS基因表达和促进NO生成,其作用强度与浓度和作用时间有关;双因素(TNF-α+LPS,LPS+IL-1β)对诱导iNOS基因表达及NO生成产生协同作用.PolymyxinB和地塞米松可部分抑制TNF-α对iNOS基因表达的诱导作用及NO生成 相似文献