Absence of tRNA-guanine transglycosylase in a human colon adenocarcinoma cell line
| Autor: | Ufuk Gündüz, Mark S. Elliott, Patricia H. Seubert, Jon R. Katze, Janet A. Houghton, Peter J. Houghton, Ronald W. Trewyn |
|---|---|
| Rok vydání: | 1992 |
| Předmět: |
Guanine
Queuosine Adenocarcinoma Biology medicine.disease_cause Mice chemistry.chemical_compound RNA Transfer Rhabdomyosarcoma Tumor Cells Cultured medicine Animals Humans Pentosyltransferases RNA Processing Post-Transcriptional Molecular Biology chemistry.chemical_classification Mutation Cell Cycle RNA Queuine Molecular biology Enzyme chemistry Biochemistry Colonic Neoplasms Transfer RNA DNA methylation Azacitidine Molecular Medicine Neoplasm Transplantation |
| Zdroj: | Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease. 1139:229-238 |
| ISSN: | 0925-4439 |
| Popis: | Queuosine (Q), found exclusively in the first position of the anticodons of tRNA(Asp), tRNA(Asn), tRNA(His) and tRNA(Tyr), is synthesized in eucaryotes by a base-for-base exchange of queuine, the base of Q, for guanine at tRNA position 34. This reaction is catalyzed by the enzyme tRNA-guanine transglycosylase (EC 2.4.2.29). We measured the specific release of queuine from Q-5'-phosphate (queuine salvage) and the extent of tRNA Q modification in 6 human tumors carried as xenografts in immune-deprived mice. Q-deficient tRNA was found in 3 of the tumors but it did not correlate with diminished queuine salvage. The low tRNA Q content of one tumor, the HxGC3 colon adenocarcinoma, prompted us to examine a HxGC3-derived cell line, GC3/M. GC3/M completely lacks Q in its tRNA and measurable tRNA-guanine transglycosylase activity; the first example of a higher eucaryotic cell which lacks this enzyme. Exposure of GC3/M cells to 5-azacytidine induces the transient appearance of Q-positive tRNA. This result suggests that at least one allele of the transglycosylase gene in GC3/M cells may have been inactivated by DNA methylation. In clinical samples, we found Q-deficient tRNA in 10 of 46 solid tumors, including 2 of 13 colonic carcinomas. |
| Databáze: | OpenAIRE |
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