PARP-1-dependent RND1 transcription induced by topoisomerase I cleavage complexes confers cellular resistance to camptothecin

Abstract

RHO GTPases regulate essential functions such as the organization of the actin cytoskeleton. The classic members cycle between an active GTP-bound and an inactive GDP-bound conformation whereas atypical members are predominantly GTP-bound. Besides their well-established role, the classic RHO GTPases RHOB and RAC1, are rapidly induced and/or activated by genotoxic stress and contribute to the DNA damage response. Here we used camptothecin, a selective topoisomerase I (TOP1) inhibitor that stabilizes TOP1 cleavage complexes (TOP1cc), to search for other potential early DNA damage-inducible RHO GTPase genes. We identified that an atypical RHO GTPase, RND1, is rapidly induced by camptothecin. RND1 induction is closely associated with the presence of TOP1cc induced by camptothecin or by DNA lesions that elevate TOP1cc levels such as UV and hydrogen peroxide. We further demonstrated that camptothecin increases RND1 gene transcription and mRNA stability. Camptothecin also increases poly(ADP-ribose) polymerase 1 (PARP-1) activity, whose inhibition reduces RND1 transcription. In addition, overexpression of RND1 increases PARP-1, suggesting a cross-talk between PARP-1 and RND1. Finally, RND1 protects cells against camptothecin-induced apoptosis, and hence favors cellular resistance to camptothecin. Together, these findings highlight RND1 as an atypical RHO GTPase early induced by TOP1cc, and show that the TOP1cc-PARP-1-RND1 pathway protects cells against apoptosis induced by camptothecin.

DNA damage and genome instability by G-quadruplex ligands are mediated by R loops in human cancer cells

“…As we reported that the topoisomerase I (Top1) poison camptothecin can transiently enhance nuclear DNA:RNA hybrids at short times in cancer cells (22), we wondered whether FG and PDS can also poison Top1. We then measured Top1-DNA cleavage complexes in U2OS cells, as described (23). The results showed that PDS and FG are not Top1 poisons (SI Appendix, Fig.…”

The RND1 Small GTPase: Main Functions and Emerging Role in Oncogenesis

“…In adenoid cystic carcinoma [52] and in breast cancer [10], the deletion of RND1 gene concerns only one of the two alleles. In several tumors, it has been reported that methylation of RND1 promoter and histone deacetylation induce the repression of RND1 gene transcription [10,46,53,54] (Figure 3). Moreover, in breast cancers, the Polycomb Repressor Complex 2 is involved in the inhibition of RND1 gene expression [10].…”

“…RND1 mRNA is also induced in human lymphocytes 15 min after ionizing irradiation [62]. Using a RT-qPCR screen of Rho GTPase expression in response to the topoisomerase I inhibitor camptothecin, we identified RND1 as a Rho GTPase gene, which is rapidly induced in the osteosarcoma U2OS cell line [53]. The poly (ADP-ribose) polymerase (PARP-1) activity is responsible for the induction of RND1 transcription after treatment with camptothecin (Figure 3).…”

“…This rapid induction of RND1 is also found in several non-tumorigenic cells, such as NIH3T3 fibroblasts, and in other tumor cells, such as U87 glioblastoma cells. In contrast, the expression of RND2 and RND3 , the two RND1 homologs, is not induced after a short treatment with camptothecin [53].…”

“…In hepatocellular carcinoma, RND1 depletion with siRNA induces the resistance of hepatocellular carcinoma cells to cisplatin, a water-soluble platinum complex [45], whereas RND1 re-expression induced by cell treatment with an inducer of promoter hypomethylation and an histone deacetylase inhibitor increases the cellular sensitivity to the Raf inhibitor, sorafenib [46]. The induction of RND1 protects osteosarcoma cells against camptothecin, likely by inhibiting apoptosis [53]. From these data, we can conclude that the effect of RND1 on cell sensitivity appears to depend on the cell type or the drug used.…”