Induction of hemoglobin synthesis by xylosyladenine in murine erythroleukemia cells. Metabolism of xylosyladenine and effects on transmethylation.
The adenosine analog xylosyladenine is a potent inducer of hemoglobin synthesis in Friend virus-infected murine erythroleukemia (MEL) cells. In cultures treated with 0.1 microM xylosyladenine and an inhibitor of adenosine deaminase, 80% of the cells accumulated hemoglobin. Under these conditions, cell growth was inhibited by 50%. No effect was observed in the absence of adenosine deaminase inhibition. An adenosine kinase-deficient MEL subline was isolated and was found to be resistant to induction by xylosyladenine. Treated cells accumulated substantial amounts of the xylofuranosyl analogs of ATP, S-adenosylmethionine, and S-adenosylhomocysteine, indicating that metabolites of xylosyladenine participate in S-adenosylmethionine-mediated transmethylation reactions. Measurements of in vivo nucleic acid methylation showed that xylosyladenine causes a marked inhibition of 2'-O-methyluridine, 2'-O-methylcytidine, 5-methyluridine, and 5-methylcytidine formation in the RNA of treated cells. DNA methylation was not inhibited. These data suggest that the xylofuranosyl analogs of S-adenosylmethionine and/or S-adenosylhomocysteine can inhibit intracellular RNA methylation in MEL cells while having little or no such effect on DNA methylation.
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