Date of Award

Summer 1988

Document Type


Degree Name

Master of Science (MS)


Chemistry & Biochemistry



Committee Director

Mark S. Elliot

Committee Member

Patricia A. Pleban

Committee Member

Roy L. Williams

Call Number for Print

Special Collections LD4331.C45C72


Queuosine, a nucleoside found exclusively in the first position of the anticodon of transfer RNA (tRNA), is generated post-transcriptionally in an exchange of guanine for queuine by the modifying enzyme tRNA-guanine ribosyltransferase. Phorbol ester tumor promoters were shown to induce queuine hypomodified tRNA, and that phorbol ester action was due, in part, to inhibition of queuine transport across the cell membrane. An unidentified protein designated conditioned medium factor (CMF) that potentiated a phorbol-induced inhibition of queuine uptake was also documented. We suggest here that phorbol ester-induced inhibition of queuine uptake is not a significant factor in inducing queuine-deficient tRNA although queuine uptake is mediated through a protein kinase C pathway. We propose that CMF is potentially related to an interferondependent system since interferons inhibited membrane transport of queuine seemingly independent of the previously observed phorbol ester effects. Since queuine deficient tRNA is characteristic of undifferentiated and neoplastic cells, modulation of queuine uptake may have significant implications in neoplasia.


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