Von Hippel-Lindau-coupled and transcription-coupled nucleotide excision repair-dependent degradation of RNA polymerase II in response to trabectedin.

PURPOSE: Ecteinascidin 743 (Et743; trabectedin, Yondelis) has recently been approved in Europe for the treatment of soft tissue sarcomas and is undergoing clinical trials for other solid tumors. Et743 selectively targets cells proficient for TC-NER, which sets it apart from other DNA alkylating agents. In the present study, we examined the effects of Et743 on RNA Pol II.

EXPERIMENTAL DESIGN AND RESULTS: We report that Et743 induces the rapid and massive degradation of transcribing Pol II in various cancer cell lines and normal fibroblasts. Pol II degradation was abrogated by the proteasome inhibitor MG132 and was dependent on TC-NER. Cockayne syndrome (CS) cells and xeroderma pigmentosum (XP) cells (XPD, XPA, XPG, and XPF) were defective in Pol II degradation, whereas XPC cells whose defect is limited to global genome NER in nontranscribing regions were proficient for Pol II degradation. Complementation of the CSB and XPD cells restored Pol II degradation. We also show that cells defective for the VHL complex were defective in Pol II degradation and that complementation of those cells restores Pol II degradation. Moreover, VHL deficiency rendered cells resistant to Et743-induced cell death, a similar effect to that of TC-NER deficiency.

CONCLUSION: These results suggest that both TC-NER-induced and VHL-mediated Pol II degradation play a role in cell killing by Et743.