Article
Identification of ATPases pontin and reptin as telomerase components essential for holoenzyme assembly.
Department of Medicine, Stanford School of Medicine, Stanford, CA 94305, USA.
Cell (impact factor:
32.4).
04/2008;
132(6):945-57.
DOI:10.1016/j.cell.2008.01.019
pp.945-57
Source: PubMed
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Article: CTX-M-15 extended-spectrum (beta)-lactamase from Nigerian Klebsiella pneumoniae.
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ABSTRACT: In this study, extended-spectrum beta-lactamases (ESBLs) were characterized from 30 selected multidrug-resistant Klebsiella pneumoniae strains isolated from patients with community-acquired urinary tract infections from Southwest Nigeria. The beta-lactamases were phenotypically characterized using isoelectric focusing, genotypically characterized using PCR assays and hybridization of the PCR products. Two of the bla(CTX-M) genes were completely sequenced. The location of the CTX-M-type genes was determined using transformation, DNA-DNA hybridization, PCR assays and hybridization of the PCR products from the Escherichia coli transformants. All 30 isolates produced at least one beta-lactamase. Seventeen of the isolates were resistant to cefotaxime, and had > or =100-fold reduction in susceptibility with cefotaxime plus clavulanic acid (4 mg/L), indicating the presence of an ESBL. The 17 isolates were shown to have bla(CTX-M) genes that were associated with large plasmids (> or =58 kb), which also carried a tetracycline resistance gene, tet(A), and various aminoglycoside resistance genes. Two CTX-M-type genes were sequenced and had amino acid sequences indistinguishable from previously sequenced CTX-M-15 beta-lactamases. The ISEcp1 element was located upstream of bla(CTX-M-15) in the same position as previously described. In addition, 23 of the isolates produced TEM beta-lactamases, 27 produced SHV beta-lactamases and four produced AmpC beta-lactamases. Thirty K. pneumoniae produced multiple beta-lactamases, with 57% producing CTX-M enzymes. This is the first characterization of CTX-M-15-positive K. pneumoniae in Western Africa.Journal of Antimicrobial Chemotherapy 01/2006; 57(1):24-30. · 5.07 Impact Factor -
Article: Saccharomyces cerevisiae telomerase is an Sm small nuclear ribonucleoprotein particle.
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ABSTRACT: Activation of the chromosome end-replicating enzyme telomerase can greatly extend the lifespan of normal human cells and is associated with most human cancers. In all eukaryotes examined, telomerase has an RNA subunit, a conserved reverse transcriptase subunit and additional proteins, but little is known about the assembly of these components. Here we show that the Saccharomyces cerevisiae telomerase RNA has a 5'-2,2,7-trimethylguanosine (TMG) cap and a binding site for the Sm proteins, both hallmarks of small nuclear ribonucleoprotein particles (snRNPs) that are involved in nuclear messenger RNA splicing. Immunoprecipitation of telomerase from yeast extracts shows that Sm proteins are assembled on the RNA and that most or all of the telomerase activity is associated with the Sm-containing complex. These data support a model in which telomerase RNA is transcribed by RNA polymerase II and 7-methylguanosine-capped, binds the seven Sm proteins, becomes TMG-capped and picks up the other protein subunits. We conclude that the functions of snRNPs assembled by this pathway are not restricted to RNA processing, but also include chromosome telomere replication.Nature 10/1999; 401(6749):177-80. · 36.28 Impact Factor -
Article: Characterization and subcellular compartmentation of recombinant 4-hydroxyphenylpyruvate dioxygenase from Arabidopsis in transgenic tobacco.
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ABSTRACT: 4-Hydroxyphenylpyruvate dioxygenase (4HPPD) catalyzes the formation of homogentisate (2,5-dihydroxyphenylacetate) from p-hydroxyphenylpyruvate and molecular oxygen. In plants this enzyme activity is involved in two distinct metabolic processes, the biosynthesis of prenylquinones and the catabolism of tyrosine. We report here the molecular and biochemical characterization of an Arabidopsis 4HPPD and the compartmentation of the recombinant protein in chlorophyllous tissues. We isolated a 1508-bp cDNA with one large open reading frame of 1338 bp. Southern analysis strongly suggested that this Arabidopsis 4HPPD is encoded by a single-copy gene. We investigated the biochemical characteristics of this 4HPPD by overproducing the recombinant protein in Escherichia coli JM105. The subcellular localization of the recombinant 4HPPD in chlorophyllous tissues was examined by overexpressing its complete coding sequence in transgenic tobacco (Nicotiana tabacum), using Agrobacterium tumefaciens transformation. We performed western analyses for the immunodetection of protein extracts from purified chloroplasts and total leaf extracts and for the immunocytochemistry on tissue sections. These analyses clearly revealed that 4HPPD was confined to the cytosol compartment, not targeted to the chloroplast. Western analyses confirmed the presence of a cytosolic form of 4HPPD in cultured green Arabidopsis cells.Plant physiology 05/1999; 119(4):1507-16. · 6.53 Impact Factor
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Keywords
additional enzymes
adds telomere
affinity purification
alternative approaches
ATPases pontin
essential telomerase components
human telomerase function
inhibiting telomerase
multisubunit ribonucleoprotein
pontin
Pontin interacts
S phase
telomerase action
telomerase assembly
telomerase biogenesis
telomerase components
telomerase reverse transcriptase
telomerase RNA component
TERC-binding protein dyskerin
unanticipated requirement
