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B A Carlson

Publications and source records attributed to B A Carlson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Recruitment of TBP or TFIIB to a promoter proximal position leads to stimulation of RNA polymerase II transcription without activator proteins both in vivo and in vitro.

Eukaryotic transcriptional activators may function, at least in part, to facilitate the assembly of the RNA polymerase II (pol II) preinitiation complex at the core promoter region through their interaction with a subset of components of the basal transcription machinery. Previous studies have shown that artificial tethering of TATA-binding protein (TBP) to the promoter region is sufficient to stimulate pol II transcription in yeast. To test whether this phenomenon is a general one in eukaryotic pol II transcription, the DNA-binding domain of yeast GAL4 was fused to either Xenopus laevis TBP or TFIIB in order to enable these factors to be efficiently positioned near the transcription start site in a GAL4-binding site-dependent manner. We found that GAL4-xTBP as well as GAL4-xTFIIB directed an increased level of transcription without involvement of the transcriptional activator, suggesting that incorporation of these basal factors into a preinitiation complex (PIC) is a major rate-limiting step accelerated by activator proteins in metazoans. These results show that transcription activation by artificial recruitment of basal transcription machinery can be observed in general among eukaryotic transcription both in vivo and in vitro. Furthermore, failure of recovery of transcription by adding GAL4-xTFIIB after depletion of endogenous TBP with TATA oligo competitor suggests that recruitment of TBP cannot be bypassed for Pol II transcription.

Animals↗
PubMed1999

Transfer RNA modification status influences retroviral ribosomal frameshifting.

The possibility of whether tRNAs with and without a highly modified base in their anticodon loop may influence the level of retroviral ribosomal frameshifting was examined. Rabbit reticulocyte lysates were programmed with mRNA encoding UUU or AAC at the frameshift site and the corresponding Phe tRNA with or without the highly modified wyebutoxine (Y) base on the 3' side of its anticodon or Asn tRNA with or without the highly modified queuine (Q) base in the wobble position of its anticodon added. Phe and Asn tRNAs without the Y or Q base, respectively, stimulated the level of frameshifting, suggesting that the frameshift event is influenced by tRNA modification status. In addition, when AAU occurred immediately upstream of UUU as the penultimate frameshift site codon, addition of tRNAAsn without the Q base reduced the stimulatory effect of tRNAPhe without the Y base, whereas addition of tRNAAsn with the Q base did not alter the stimulatory effect. The addition of tRNAAsn without the Q base and tRNAPhe with the Y base inhibited frameshifting. The latter studies suggest an interplay between the tRNAs decoded at the penulimate frameshift and frameshift site codons that is also influenced by tRNA modification status. These data may be intrepreted as indicating that a hypomodified isoacceptor modulates frameshifting in an upward manner when utilized at the frameshift site codon, but modulates frameshifting in a downward manner when utilized at the penultimate frameshift site codon.

Animals↗
PubMed1998

The essential Gcd10p-Gcd14p nuclear complex is required for 1-methyladenosine modification and maturation of initiator methionyl-tRNA.

Gcd10p and Gcd14p are essential proteins required for the initiation of protein synthesis and translational repression of GCN4 mRNA. The phenotypes of gcd10 mutants were suppressed by high-copy-number IMT genes, encoding initiator methionyl tRNA (tRNAiMet), or LHP1, encoding the yeast homolog of the human La autoantigen. The gcd10-504 mutation led to a reduction in steady-state levels of mature tRNAiMet, attributable to increased turnover rather than decreased synthesis of pre-tRNAiMet. Remarkably, the lethality of a GCD10 deletion was suppressed by high-copy-number IMT4, indicating that its role in expression of mature tRNAiMet is the essential function of Gcd10p. A gcd14-2 mutant also showed reduced amounts of mature tRNAiMet, but in addition, displayed a defect in pre-tRNAiMet processing. Gcd10p and Gcd14p were found to be subunits of a protein complex with prominent nuclear localization, suggesting a direct role in tRNAiMet maturation. The chromatographic behavior of elongator and initiator tRNAMet on a RPC-5 column indicated that both species are altered structurally in gcd10Delta cells, and analysis of base modifications revealed that 1-methyladenosine (m1A) is undetectable in gcd10Delta tRNA. Interestingly, gcd10 and gcd14 mutations had no effect on processing or accumulation of elongator tRNAMet, which also contains m1A at position 58, suggesting a unique requirement for this base modification in initiator maturation.

Adenosine↗
PubMed1998

Rabbit beta-globin is extended beyond its UGA stop codon by multiple suppressions and translational reading gaps.

Translational reading gaps occur when genetic information encoded in mRNA is not translated during the normal course of protein synthesis. This phenomenon has been observed thus far only in prokaryotes and is a mechanism for extending the reading frame by circumventing the normal stop codon. Reading frames of proteins may also be extended by suppression of the stop codon mediated by a suppressor tRNA. The rabbit beta-globin read-through protein, the only known, naturally occurring read-through protein in eukaryotes, was sequenced by ion trap mass spectrometry to determine how the reading frame is extended. Seven different proteolytic peptide fragments decoded by the same sequence that spans the UGA stop codon of rabbit beta-globin mRNA were detected. Three of these peptides contain translational reading gaps of one to three amino acids that correspond to the UGA stop codon site and/or one or two of the immediate downstream codons. To our knowledge, this is the first reported example of the occurrence of reading gaps in protein synthesis in eukaryotes. This event is unique in that it is associated with bypasses involving staggered lengths of untranslated information. Four of the seven peptides contain serine, tryptophan, cysteine, and arginine decoded by UGA and thus arise by suppression. Serine is donated by selenocysteine tRNA, and it, like the other tRNAs, has previously been shown to suppress UGA in vitro in mammals, but not in vivo.

Amino Acid Sequence↗
PubMed1997

Replenishment of selenium deficient rats with selenium results in redistribution of the selenocysteine tRNA population in a tissue specific manner.

We reported previously that the selenium status of rats influences both the steady-state levels and distributions of two selenocysteine tRNA isoacceptors and that these isoacceptors differ by a single methyl group attached to the ribosyl moiety at position 34. In this study, we demonstrate that repletion of selenium-deficient rats results in a gradual, tissue-dependent shift in the distribution of these isoacceptors. Rats fed a selenium-deficient diet possess a greater abundance of the species unmethylated on the ribosyl moiety at position 34 compared to the form methylated at this position. A redistribution of the Sec-tRNA isoacceptors occurred in tissues of selenium-supplemented rats whereby the unmethylated form gradually shifted toward the methylated form. This was true in each of four tissues examined, muscle, kidney, liver and heart, although the rate of redistribution was tissue-specific. Muscle manifested a predominance of two minor serine isoacceptors under conditions of extreme selenium-deficiency which also appeared to respond to selenium. Ribosomal binding studies revealed that one of the two additional isoacceptors decodes the serine codeword, AGU, and the second decodes the serine codeword, UCU. Interestingly, muscle and heart were the slower tissues to return to a 'selenium adequate' tRNA distribution pattern.

Animals↗
PubMed1997

Paranasal sinus fungus balls.

BACKGROUND: Paranasal sinus fungus balls (mycetomas) are a form of fungal sinus infection distinct from allergic fungal sinusitis, fulminant invasive fungal disease, and paranasal aspergillus granulomas. METHODS: The Mayo Clinic surgical pathology files of inflammatory sinus specimens from 1984 to 1994 were examined. Twenty-nine paranasal sinus fungus balls were identified. Cases of allergic fungal sinus and invasive fungal disease were excluded. RESULTS: The fungus ball occurred in 11 men and 18 women, with an age range of 28 to 86 years, mean 64 years. Sinuses involved included maxillary (20 cases), sphenoid (10 cases), ethmoid (9 cases), and frontal (6 cases). In 12 patients, multiple sinuses were involved in a variety of combinations. By culture the most common pathogens were Aspergillus fumigatus and Aspergillus flavus. Treatment was by a variety of surgical procedures. Follow-up in 28 patients showed two recurrences and three deaths due to intracerebral bleed as a complication of surgery. These deaths occurred in patients with sphenoid sinus fungus balls. CONCLUSIONS: Paranasal sinus fungus balls occurs in an elderly population and have a female predominance. They have a low morbidity and recurrence rate. Death can occur in sphenoid sinus lesions as a complication of surgery.

Adult↗
PubMed1997

Selenocysteine tRNAs as central components of selenoprotein biosynthesis in eukaryotes.

Selenocysteine (Sec) tRNAs serve as carrier molecules for the biosynthesis of Sec from serine and to donate Sec to protein in response to specific UGA codons. In this study, we describe the current status of Sec tRNAs in higher animals and further we examine: (i) the Sec tRNA population in Drosophila; (ii) transcription of the Sec tRNA in vivo (in Xenopus oocytes) and in vitro (in Xenopus oocyte extracts); (iii) the effect of selenium on the Sec tRNA population in various rat tissues following replenishment of extremely selenium deficient rats with this element; and (iv) the biosynthesis of the modified bases on Sec tRNA in Xenopus oocytes.

Animals↗
PubMed1996

Flavopiridol induces G1 arrest with inhibition of cyclin-dependent kinase (CDK) 2 and CDK4 in human breast carcinoma cells.

Flavopiridol (L86-8275), a N-methylpiperidinyl, chlorophenyl flavone, can inhibit cell cycle progression in either G1 or G2 and is a potent cyclin-dependent kinase (CDK) 1 inhibitor. In this study, we used MCF-7 breast carcinoma cells that are wild type for p53 and pRb positive and contain CDK4-cyclin D1 and MDA-MB-468 breast carcinoma cells that are mutant p53, pRb negative, and lack CDK4-cyclin D1 to investigate the G1 arrest produced by Flavopiridol. Recombinant CDK4-cyclin D1 was inhibited potently by Flavopiridol (Kiapp, 65 nM), competitive with respect to ATP. Surprisingly, CDK4 immunoprecipitates derived from Flavopiridol-treated MCF-7 cells (3 h, 300 nM Flavonolpiridol) had an approximately 3-fold increased kinase activity compared with untreated cells. Cyclin D and CDK4 levels were not different at 3 hr, but cyclin D levels and CDK4 kinase activity decreased thereafter. The phosphorylation state of pRb was shifted from hypercoincident to hypocoincident with the development of G1 arrest. Asynchronous MDA-MB-468 cells were inhibited in cell cycle progression at both G1 and G2 by Flavopiridol. Flavopiridol inhibited the in vitro kinase activity of CDK2 using an immune complex kinase assay (IC50, 100 nM at 400 microM ATP). Immunoprecipitated CDK2 kinase activity from either MCF-7 or MDA-MB-468 cells exposed to Flavopiridol (300 nM) for increasing time showed an initial increased activity (approximately 1.5-fold at 3 h) compared with untreated cells, followed by a loss of kinase activity to immeasurable levels by 24 h. This increased immunoprecipitated kinase activity was dependent on the Flavopiridol concentration added to intact cells and was associated with a reduction of CDK2 tyrosine phosphorylation. Cyclin E and A levels were not altered to the same extent as cyclin D, and neither CDK4 nor CDK2 levels were changed in response to Flavopiridol. Inhibition of the CDK4 and/or CDK2 kinase activity by Flavopiridol can therefore account for the G1 arrest observed after exposure to Flavopiridol.

Amino Acid Sequence↗
PubMed1996

Rapidly progressive dementia caused by nonenhancing primary lymphoma of the central nervous system.

A 76-year-old woman had rapidly progressive dementia over 4 months. Proton density- and T2-weighted MR images of the head showed increased signal in the periventricular and subcortical white matter of both cerebral hemispheres and the brain stem. Enhancement was not seen after administration of contrast material. Because of the rapid progression of the dementia and increasing signal abnormalities within the cerebral white matter, the patient underwent a craniotomy with biopsies of the right frontal lobe. Pathologic specimens were positive for malignant large-cell lymphoma, B-cell phenotype. The MR appearance is atypical for primary lymphoma of the central nervous system.

Aged↗
PubMed1995

Apoptosis in 7-hydroxystaurosporine-treated T lymphoblasts correlates with activation of cyclin-dependent kinases 1 and 2.

7-Hydroxystaurosporine (UCN-01) is a potent inhibitor of protein kinase C (PKC) isozymes alpha, beta, and gamma [Seynaeve et al., Mol. Pharmacol, 45: 1207-1214, 1994] that also has antitumor effects in vivo. To determine whether inhibition of PKC can be related to inhibition of cell growth with induction of apoptosis, we compared the effects of UCN-01 to those of the highly selective bisindolylmaleimide PKC antagonist GF 109203X in leukemic T-cell lines. Both compounds potently inhibited PKC activity when added to T-cell membrane preparations and reversed phorbol ester-induced c-fos gene expression in intact cells. However, whereas UCN-01 potently inhibited growth of Jurkat, Molt-3, Molt-4, and Hut-78 cells (IC50 = 20-65 nM, irreversible after 24 h of exposure), GF 109203X had IC50s for cell growth of 3.6-5.0 muM. Less than 3 h after addition, UCN-01 but not GF 109203X-treated cells displayed loss of cells with G2-M DNA content, appearance of a hypodiploid DNA fraction, and evidence of internucleosomal DNA fragmentation. Six h after treatment, cells appeared to accumulate with S-phase DNA content. These effects correlated with selective UCN-01 but not GF 109203X-induced decrease in total and tyrosine phosphorylation of cyclin-dependent kinases (cdks) 1 and 2, and with increases in the histone H1 kinase activities of cdk1 and cdk2. UCN-01 was relatively less potent in inhibition of properly activated cdk1 and cdk2 when added in vitro to H1 kinase assays (IC50 = 1000 and 600 nM, respectively). We conclude that inhibition of PKC alone is not sufficient to account for the actions of UCN-01 and are led to the hypothesis that inappropriate cdk activation either correlates with or actually mediates cell growth inhibition with apoptosis in T lymphoblasts exposed to UCN-01.

Alkaloids↗
PubMed1994

Potent inhibition of CDC2 kinase activity by the flavonoid L86-8275.

L86-8275 [(-) cis-5,7-dihydroxy-2-(2-chlorophenyl)-8[4-(3-hydroxy-1- methyl)-piperidinyl]-4H-benzopyran-4-one] directly inhibits immunoprecipitated Cdc2 kinase activity from G2/M synchronized MDA-MB-468 breast carcinoma cells and is at least 250-fold more potent than either quercetin or genistein. Purified sea-star Cdc2 kinase (IC50 = 0.5 microM) was inhibited with a similar potency to immunoprecipitated Cdc2 kinase from MDA-MB-468 cells (IC50 = 0.4 microM). This inhibition was competitive with respect to ATP (KiATP = 0.041 microM) and noncompetitive with respect to a synthetic peptide substrate, CDK1S1 (AAKAKKTPKKAKK-CONH2, KiCDK1S1 = 0.14 microM). These data suggest L86-8275 as a lead structure for the development of inhibitors of the cyclin-dependent kinases.

Adenosine Triphosphate↗
PubMed1993

Static secondary ion mass spectrometry of adsorbed proteins.

Static secondary ion mass spectrometry (SIMS) was used to analyze proteins adsorbed to biomaterial surfaces. A spectral interpretation protocol was established by examining homopolymers of 16 amino acids. This protocol allows for the assignment of peaks unique to the various amino acids. Static SIMS was used to analyze plasma proteins adsorbed to titanium. The various factors that contributed to the relative intensities observed in the spectra were explored. The potential application of the technique for studying protein-fouled materials was investigated by analyzing a fouled sensor membrane.

Adsorption↗
PubMed1990

Lasers in podiatry and orthopedics.

Laser use in podiatry has proved very beneficial for many conditions of the foot. Laser use in orthopedics is beginning to evolve as the benefits that can be derived from the this technology are being realized. The CO2, Nd:YAG, and argon systems are being used and investigated, and new applications are being introduced.

Foot Diseases↗
PubMed1987

Complications associated with laser surgery.

All lasers are classified according to their potential for injury. Because medical lasers fall into the category having the greatest hazard potential, appropriate safeguards must be planned and undertaken. This article addresses the complications associated with the photoablative and thermal effects of lasers. Despite the laser's potential for injury, however, the probability of serious damage is negligible if the modality is used intelligently by the informed physician.

Equipment Failure↗
PubMed1985

Using surveys for management and measurement of health in developing countries.

National household surveys have been a basic statistical feature for many decades in the industrialized countries and more recently in the developing world. This paper deals with the potential of national household surveys for obtaining health information in developing countries. In this regard the United Nations National Household Survey Capability Programme (NHSCP) aims at collaborating with developing countries to establish a continuing flow of integrated statistics.

Data Collection↗