Enzymatic processing of platinated RNAs

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Cisplatin is a widely used antitumor drug that primarily targets DNA.
• The interaction of cisplatin with RNA and its impact on RNA processing enzymes are not well understood.
• Understanding RNA-Pt adducts is crucial for comprehending the broader cellular effects of platinum-based chemotherapy.

Purpose of the Study:

• To investigate how platinum-II (Pt(II)) adducts on RNA affect the activity of key RNA processing enzymes.
• To determine the influence of [Pt(NH(3))(2)](2+)-RNA adducts on phosphodiesterases, endoribonucleases, and reverse transcriptase.
• To explore the potential contribution of RNA platination to the cellular effects of cisplatin.

Main Methods:

• Synthesis of RNA oligonucleotides with specific platinum adducts.
• Assays to measure the activity of 3'-->5' and 5'-->3' phosphodiesterases.
• Enzymatic assays using a purine-specific endoribonuclease (RNase U2) and a reverse transcriptase.
• Chemical reversal of platinum-RNA adducts using thiourea.

Main Results:

• Single Pt(II) adducts on RNA oligonucleotides blocked exonucleolytic digestion.
• Most endoribonucleolytic cleavages were disrupted by platinum adducts, with RNase U2 showing tolerance to platination at the GA site.
• Platinum adducts on more complex RNA structures inhibited reverse transcription, indicating interference with RNA sequence information transfer.
• Thiourea was demonstrated to effectively reverse cisplatin-RNA adducts.

Conclusions:

• Cisplatin-RNA adducts significantly impair the function of essential RNA processing enzymes.
• Platinum-induced disruption of RNA processing may contribute to the overall cytotoxicity of cisplatin.
• The findings highlight RNA as a potential target for cisplatin and suggest RNA processing alterations as a mechanism of action.
• Thiourea provides a valuable chemical tool for further investigation of cisplatin-RNA interactions.