Transfer RNA cleavages by onconase reveal unusual cleavage sites.
Onconase, a protein from amphibian eggs and a homologue of pancreatic ribonuclease (RNase) superfamily, is cytotoxic, exhibits antitumor and antiviral activity, and is in phase III clinical trials. It has been shown to predominantly target cellular tRNA on its entry into mammalian cells (Saxena, S. K., Sirdeshmukh, R., Ardelt, W., Mikulski, S. M., Shogen, K., and Youle, R. J. (2002) J. Biol. Chem. 277, 15142-15146). Cleavage site mapping using natural tRNA substrates, in vitro, revealed predominant cleavage sites at UG and GG residues. Cleavages at UG or the less intense cleavages at CG sites are consistent with the known base specificity of onconase. However, predominance of cleavages at selected G-G bonds is unusual for a homologue of pancreatic RNases. Interestingly, in at least three of the four tRNA substrates studied, the predominant cleavages mapped in the triplet UGG located in the context of the variable loop or the D-arm of the tRNA. The cleavage specificity of onconase observed by us thus indicates another special feature of this enzyme, which may be relevant to its cellular actions.
Suhasini
Avvaru N
AN
Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.
Sirdeshmukh
Ravi
R
D000818:Animals; D001483:Base Sequence; D004926:Escherichia coli / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011500:Protein Synthesis Inhibitors / Q000378:metabolism; D012313:RNA / Q000737:chemistry*; D012343:RNA, Transfer / Q000737:chemistry / Q000378:metabolism; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D012259:Ribonuclease, Pancreatic / Q000737:chemistry; D012260:Ribonucleases / Q000737:chemistry* / Q000502:physiology*
D011500:Protein Synthesis Inhibitors; D012313:RNA; D012343:RNA, Transfer; D012260:Ribonucleases; D012259:Ribonuclease, Pancreatic; C058703:ranpirnase