Inhibition of pre-mRNA splicing by cisplatin and platinum analogs.
Our previous study demonstrated that the anticancer agent cis-diamminedichloroplatinum (II) (cis-DDP) inhibited the self-splicing activity of the Tetrahymena rRNA. The present study investigated the effects of cis-DDP on pre-mRNA splicing using a HeLa cell nuclear extract. A 2-h exposure of cis-DDP inhibited the splicing of the human B-globin pre-mRNA in a concentration-dependent manner. The concentration required for 50% inhibition of splicing (IC50) was 51 microM. Complete inhibition of spliceosome assembly occurred when the extracts were incubated with 150 microM cis-DDP. The inhibition of splicing by cis-DDP occurred at early events during spliceosome formation and to a greater extent if the extract was pre-incubated with cis-DDP in the absence of pre-mRNA. Splicing was inhibited when both pre-mRNA and cis-DDP were added simultaneously to the reaction mixture but not when cis-DDP was added 30 min after splicing was initiated with pre-mRNA. Clinically useful platinum analogs (ormaplatin, carboplatin, cis-tetraplatin and iproplatin) as well as the clinically ineffective Pt(dien)C1+, compound were tested for their ability to inhibit pre-mRNA splicing. The Pt(dien)C1+ compound, which acts in a monofunctional manner only, failed to inhibit splicing. A varying degree of splicing inhibition was observed for the other platinum analogs studied; the inhibitory activity decreased in the following order: ormaplatin > cis-tetraplatin > cis-DDP > iproplatin > carboplatin. We describe a novel mechanism that may be involved in the activity and/or toxicity of platinum agents.
Schmittgen
Thomas D
TD
Department of Pharmaceutical Sciences, College of Pharmacy, Pullman, WA 99164, USA.
Ju
Jing-Fang
JF
Danenberg
Kathleen D
KD
Danenberg
Peter V
PV
D000970:Antineoplastic Agents / Q000494:pharmacology*; D016190:Carboplatin / Q000494:pharmacology; D002467:Cell Nucleus / Q000378:metabolism; D002945:Cisplatin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008956:Models, Chemical; D009944:Organoplatinum Compounds / Q000494:pharmacology; D012326:RNA Splicing / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism; D017381:Spliceosomes / Q000378:metabolism; D013997:Time Factors
D000970:Antineoplastic Agents; D009944:Organoplatinum Compounds; D012333:RNA, Messenger; C032799:chlorodiethylenetriamine platinum; C023359:iproplatin; D016190:Carboplatin; D002945:Cisplatin; C049777:ormaplatin