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Transfer RNA cleavages by onconase reveal unusual cleavage sites

Avvaru N Suhasini1, Ravi Sirdeshmukh

  • 1Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.

The Journal of Biological Chemistry
|February 25, 2006
PubMed

Insights

Onconase, an antitumor protein, primarily cleaves transfer RNA (tRNA) at specific UG and GG sites within mammalian cells. This unusual G-G bond cleavage, particularly at UGG triplets, highlights a unique feature of onconase

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Enzymology

Background:

  • Onconase, a protein from amphibian eggs, is a homologue of pancreatic ribonuclease (RNase).
  • It exhibits cytotoxic, antitumor, and antiviral activities and is currently in phase III clinical trials.
  • Onconase has been shown to predominantly target cellular transfer RNA (tRNA) in mammalian cells.

Purpose of the Study:

  • To investigate the specific cleavage sites of onconase on natural tRNA substrates.
  • To understand the base specificity and unusual cleavage patterns of onconase.
  • To correlate cleavage specificity with onconase's cellular actions.

Main Methods:

  • In vitro cleavage site mapping using natural tRNA substrates.
  • Analysis of cleavage products to determine predominant cleavage sites.
  • Comparison of onconase cleavage specificity with known pancreatic RNase specificities.

Main Results:

  • Onconase predominantly cleaved tRNA at UG and GG residues.
  • Cleavage at CG sites was observed but less intense.
  • Unusually, predominant cleavages occurred at selected G-G bonds, particularly within UGG triplets in the variable loop or D-arm of tRNA substrates.

Conclusions:

  • Onconase exhibits a unique cleavage specificity, differing from typical pancreatic RNases, especially regarding G-G bond cleavage.
  • The predominant cleavage at UGG triplets in specific tRNA regions represents a special feature of onconase.
  • This distinct cleavage specificity may be crucial for onconase's cytotoxic and therapeutic effects in cellular actions.

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