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I Kang

Publications and source records attributed to I Kang.

48 records · Page 3Linked to original sources
PubMed1994

Affinity labeling and measurement of DNA-induced conformation change in RNA polymerase II.

The inhibition of RNA polymerase II by 8-azido-2'-O-(1-naphthalenesulfonyl)- ATP (AN-ATP) was found to be reversible in the dark and competitive with ATP, with KI = 2.2 +/- 0.2 microM and KATP = 20 +/- 0.5 microM, but noncompetitive with CTP and GTP, with dissociation constants KCTP = 4.4 +/- 0.4 microM and KGTP = 19.4 +/- 0.7 microM. Under UV irradiation the enzyme was irreversibly labeled by AN-[alpha-32P]ATP. A linear plot of the relative specific activities of labeled enzyme samples after gel filtration vs the number of labels per enzyme molecule shows that each covalent label completely inactivates an enzyme molecule. Therefore the labeling has maximal specificity at an essential specific ATP site which is not the substrate-binding site for the polymerization reaction. The fluorescent AN-ATP-labeled enzyme, with absorbance maximum at 310 nm and emission maximum at 370 nm, can still bind noncovalently a second ligand, 2'-O-dansyl-ATP, with absorbance maximum at 365 nm and emission maximum at 560 nm, at the substrate-binding site. Measurement of energy transfer between the two fluorescent labels gave R = 23.8 +/- 0.4 A as the average distance between them and Kd = 31 +/- 0.1 microM for the bound 2'-O-dansyl-ATP in the absence of DNA template. The addition of either thymus DNA or poly[d(A-T)] to the system changed these values to R = 25.6 +/- 0.4 A and Kd = 53 +/- 0.4 microM. These results indicate that the binding of RNA polymerase II to DNA template triggers a conformation change in the enzyme molecule.

Adenosine Triphosphate↗
PubMed1994

Isolation and characterization of the promoter of the human GABAA receptor alpha 1 subunit gene.

The GABAA receptor, as assessed by ligand binding and chloride flux measurement in vivo and in vitro, is down-regulated in response to chronic benzodiazepine exposure. The mRNA levels of the alpha 1 and gamma 2 subunits of the receptor are also reduced. We have isolated the promoter of the gene encoding the alpha 1 subunit of the GABAA receptor to elucidate the regulatory mechanism of its expression. A DNA segment 650 bp long has been isolated that includes 151 bp of untranslated 5' end of the cDNA sequence and 500 bp of potential promoter-enhancer region. The transcriptional activity of this DNA segment linked to the firefly luciferase gene showed a strong orientation specificity. The promoter activity was localized to a 60-bp segment by deletion mapping. Mobility shift binding assay results suggest that this segment may interact with one or more factors in HeLa cell nuclear extracts to form a transcriptional complex. Primary cultures of embryonic chick cortical cells transfected with the promoter-luciferase construct were treated chronically with lorazepam. Transcriptional activity of this promoter construct was strongly repressed by chronic administration of lorazepam.

Animals↗
PubMed1993

Electroconvulsive shock alters GABAA receptor subunit mRNAs: use of quantitative PCR methodology.

Electroconvulsive shock (ECS) may affect several neurotransmitter systems in brain, including the GABAergic inhibitory system. We used a quantitative PCR-based assay to evaluate mRNAs for five GABAa receptor subunits at 2 to 24 h after ECS. mRNAs for the alpha 1 and beta 2 subunits were significantly increased in cerebellum at 4 and 8 h after ECS, and returned to control levels at 24 h. No changes were observed in alpha 2, beta 3, gamma 1, or gamma 2 subunits, and no changes in any subunit evaluated were observed in cortex or hippocampus. These data corroborate prior results obtained for the alpha 1 subunit using Northern hybridization, and illustrate the utility of the PCR assay in quantitating low-abundance mRNAs.

Animals↗
PubMed1991

Persistent elevation in GABAA receptor subunit mRNAs following social stress.

Stress is associated with alterations in GABA/benzodiazepine binding and function. We evaluated effects of social stress on GABAA receptor subunit (alpha 1 and gamma 2) mRNAs by Northern hybridization. In cortex, no change was observed in either subunit mRNA immediately after stress, but a 4 hours mRNAs for both subunits were increased. These changes persisted for 72 hours after stress, and returned to baseline levels at 7 days. No changes in mRNAs were observed in sham-treated mice. No changes in either subunit mRNA were observed in stressed or sham-treated mice in cerebellum or hippocampus. In undefeated resident mice, mRNAs for both subunits in cortex were unaffected at 24 hours after the stress episode. Social stress is associated with increases in GABAA receptor alpha 1 and gamma 2 subunit mRNAs in cortex.

Animals↗
PubMed1991

Decreased GABAA receptor subunit mRNA concentrations following chronic lorazepam administration.

Chronic benzodiazepine administration has been associated with alterations in binding and function at the GABAA receptor. To evaluate effects of chronic benzodiazepine exposure on messenger RNA (mRNA) concentrations for several GABAA receptor subunits, we treated mice with lorazepam, 2 mg kg-1 daily for 1-28 days and evaluated mRNAs for the alpha 1 and gamma 2 subunits by Northern hybridization. In cerebral cortex, concentrations of mRNA for the alpha 1 and gamma 2 subunits were unchanged from vehicle or control after 1-10 days of lorazepam. However, after 14 days of treatment mRNA concentrations for both subunits decreased to approximately 50% of control values and remained decreased at 28 days. In contrast, no significant alterations were observed for either subunit mRNA in hippocampus or cerebellum over the same time course. Alterations in mRNAs in cortex occur after the development of tolerance and receptor downregulation in this model.

Animals↗
PubMed1991

GABAA receptor mRNAs are increased after electroconvulsive shock.

Electroconvulsive shock (ECS) has been reported to alter brain second-messengers and neurotransmitter systems, including the gamma-aminobutyric acid (GABAergic) system, and to increase messenger ribonucleic acid (mRNA) for the proto-oncogene c-fos. We evaluated mRNA for the most abundant GABAA receptor subunits, alpha 1 and gamma 2, in brain regions after a single ECS in mice. Alpha 1 and gamma 2 mRNAs were unchanged from controls at 2 hrs after ECS, but both were significantly elevated in cerebellum and hippocampus after 4 hrs. This alteration persisted in cerebellum for alpha 1 mRNA at 8 hrs, but resolved for gamma 2 mRNA in cerebellum and for both subunit mRNAs in hippocampus. No changes in mRNA were observed in cortex for either subunit and no changes in either mRNA were observed in brain regions of sham-treated mice. Thus, ECS appears to be associated with a rapid, reversible increase in GABAA receptor subunit mRNAs in several brain regions.

Animals↗
PubMed1990

An insulin response element in the glyceraldehyde-3-phosphate dehydrogenase gene binds a nuclear protein induced by insulin in cultured cells and by nutritional manipulations in vivo.

Two independent cis-acting insulin response elements (IREs) in the gene encoding glyceraldehyde-3-phosphate dehydrogenase [D-glyceraldehyde-3-phosphate: NAD+ oxidoreductase (phosphorylating), EC 1.2.1.12], designated IRE-A and IRE-B, are sufficient to direct insulin-inducible gene expression. Using the electrophoretic mobility shift assay, a 4-fold increase in the amount of IRE-A DNA bound to nuclear proteins was detected when extracts isolated from insulin-stimulated differentiated 3T3-L1 cells or from the liver of rats refed a high-carbohydrate/low-fat diet after a 72-hr fast were compared to control nuclear extracts. The points of contact between protein and IRE-A DNA may represent a sequence recognized by at least one class of insulin-sensitive transcription factor(s).

Animals↗
PubMed1984

CII-dependent activation of the pRE promoter of coliphage lambda fused to the Escherichia coli galK gene.

Using a cloning vector designed for the study of prokaryotic promoters by fusion to the Escherichia coli galactokinase gene (galK), we have constructed a plasmid in which the lambda pRE promoter controls galactokinase expression. A galK- host containing this plasmid has a Gal- phenotype since transcription from pRE requires activation by the lambda CII protein. When CII protein is provided by a prophage, galactokinase is synthesized at a rate dependent on the concentration of CII protein. A second plasmid was constructed in which the pRE promoter from phage 21 controls galactokinase expression. Transcription of the galK gene in this plasmid requires the phage 21 CII protein. Using this system, we demonstrate that the lambda and 21 pRE promoters are highly selective for their corresponding CII proteins. However, a cross-reaction between 21 pRE and the lambda CII protein was observed. In addition, we transferred the pRE-galK fusion unit from the plasmid to a phage, and then to the host chromosome in single copy. Galactokinase expression in this single copy pRE-galK system is also dependent on CII protein, which may be provided from a multicopy plasmid. The high concentration of CII protein provided by the plasmid results in maximal expression of the pRE-galK transcription unit. In this second system low levels of CII activity from CII- mutants are amplified and can be readily detected.

Bacterial Proteins↗
PubMed1977

Silicone rubber band for laparoscopic tubal sterilization.

In 1974, Yoon and associates (Am J Obstet Gynecol 120:132, 1974) described a new approach in which laparoscopic tubal occlusion was accomplished by utilizing the silicone rubber band technique. Recognizing the great advantages of the new technique in eliminating potential thermal injury associated with electrocoagulation, the authors have utilized the Yoon silicone rubber band technique in these institutions over the past 20 months. Thus far the procedure has been performed in 304 patients without any major complications. In the hope of eliminating and/or reducing possible pregnancy-failure rates, in 110 cases. In addition to application of the silicone band, the tube within the band was transected with non-electrical Seigler biopsy forceps. This, we believe, should provide an interesting long-term comparative study.

Female↗