The irradiation of native or unmodified yeast tRNAphe by short wavelength UV light (260 nM) results In an Intramolecular crosslink that has been mapped to occur between C48 In the variable loop and U59 in the T loop. Photo-reversibility of the crosslink and the absence of fluorescent photo adducts suggest that the crosslink product is a cytidine-uridine cyclobutane dimer. This Is consistent with the relative geometries of C48 and U59 in the crystal structure of yeast tRNAphe. Evaluation of the crosslinking efficiency of the mutants of tRNAPhe indicates that the reaction depends on the correct tertiary structure of the RNA.
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