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Separation And Quantification Of Queuine-Modified And Unmodified Transfer Rna Isoacceptors, Jorge Miguel Pereira De Oliveira Da Silva Santos
Separation And Quantification Of Queuine-Modified And Unmodified Transfer Rna Isoacceptors, Jorge Miguel Pereira De Oliveira Da Silva Santos
Chemistry & Biochemistry Theses & Dissertations
The discovery of a base-exchange modification in the first position of the anticodon of four transfer RNA (tRNA) isoacceptor families has been shown to be correlated with a decrease in the rate of cell division in several tumorigenic tissues. This fact led to the hypothesis that wobbling in the anticodon might be a control point wich mediates the rate of translation. A suitable method for separation of different tRNA isoacceptor families had to be created in order to generate a means for quantitatively measuring degrees of this base modification in tRNA. Radio labelled amino acids were used to charge tRNA …
Separation Of Transfer Rna Isoacceptors By Reversed Phase W-Porex C-4 High Pressure Liquid Chromatography, Christine D. Witte
Separation Of Transfer Rna Isoacceptors By Reversed Phase W-Porex C-4 High Pressure Liquid Chromatography, Christine D. Witte
Chemistry & Biochemistry Theses & Dissertations
Transfer RNA (tRNA), is a complex class of small molecules which have been proven to play a major role in protein synthesis. Transfer RNA is composed of 20 families of isoacceptors which may recognize only one particular amino acid. This family of isoacceptors may differ from each other by primary sequence or modified nucleosides. Queuine is a modified nucleoside which is found in the anticodon regions of tRNA isoacceptors for asparagine, aspartic acid, tyrosine and histidine. Queuine has gained the interest of many researchers since queuine deficient tRNA was found in many neoplastic and undifferentiated cell-lines. It is often difficult …
Regulation Of Queuine Insertion Into Transfer Rna: Effects Of Tumor Promoters, Bonnie Jean Brooks
Regulation Of Queuine Insertion Into Transfer Rna: Effects Of Tumor Promoters, Bonnie Jean Brooks
Chemistry & Biochemistry Theses & Dissertations
The purpose of this study was to treat normal human fibroblasts with known tumor promoters and observe queuine modification of tRNA. The queuine insertion enzyme, tRNAguanine ribosyltransferase, was studied in vivo and in vitro. Tumor promoter-treated human fibroblast cultures exhibited variable queuine-insertion rates with a transient inhibition that correlated with variable levels of queuine modified tRNA over time in culture from passages 3 — 8. In contrast the in vitro studies showed that phorbol cetera and saccharin actually increased insertion with strong evidence indicating phosphorylation as a positive modulating force of the enzyme activity. It is proposed that chronic stimulation …
Hypoxanthine-Induced Differentiation Of Cultured Human Leukemia Cells, Gayle Jennette Singleton
Hypoxanthine-Induced Differentiation Of Cultured Human Leukemia Cells, Gayle Jennette Singleton
Chemistry & Biochemistry Theses & Dissertations
Human cultured leukemia cells appear to have a decreased amount of inosine in their tRNA. When cells with inosine deficient tRNA are placed in a hypoxanthine fortified media, they incorporate hypoxanthine into their tRNA by the action of the enzyme tRNA-hypoxanthine ribosyl transferase. This generates the nucleoside inosine in the tRNA. The cultured human leukemia cell lines, CCRF-CEM, HL-60, and HGPRT(-) HL- 60, incorporate hypoxanthine into their tRNA, as determined by tRNA isolation, hydrolysis, and HPLC analysis. Hypoxanthine treatment dramatically inhibited cell growth in conjunction with partial induction of differentiation in the CCRF-CEM, HL-60, and HGPRT ( - ) HL-60 …