SEQUENCE-SPECIFIC HYDROLYSIS OF YEAST TRNA(PHE) MEDIATED BY METAL-FREE BLEOMYCIN

Bleomycin A(2) (BLM) was found to mediate sequence specific hydrolysis of tRNA(Phe) in, th, absence of added metal ions. BLM A(2) promoted phosphodiester bond hydrolysis 3' to the pyrimidine residue at all resolved Py-Pu sites not involving modified bases, as demonstrated by high-resolution electrophoretic analysis of 5'- and 3'-P-32-end-labeled substrates. The reaction proceeded with surprising facility, approaching in efficiency that of oxidative strand scission mediated by the Fe-II. BLM A(2) complex. By the use of a number of BLM congeners, as well as a study of the time, temperature, and salt dependence of the hydrolysis, it was shown that in many respects the hydrolytic reaction parallels the oxidative degradation of RNA and DNA mediated by metallobleomycins. Thus, in contrast to the well-characterized oxidative degradation of DNA and RNA by bleomycin studied for two decades, the present report documents the ability of certain metal-free bleomycins to mediate RNA hydrolysis.