Molecular basis of CX-5461-induced DNA damage response in primary vascular smooth muscle cells

Molecular basis of CX-5461-induced DNA damage response in primary vascular smooth muscle cells

Blog Article

Our previous studies have shown that the novel selective RNA polymerase I inhibitor CX-5461 suppresses proliferation of vascular smooth muscle cells, mainly by inducing DNA damage response (DDR), including activations of ataxia telangiectasia AMARE mutated (ATM)/ATM and Rad3-related (ATR) and p53.Currently, there is no information about the molecular mechanism(s) underlying CX-5461-induced DDR in vascular cells, while the results obtained in cancer cells and immortalized cell lines are controversial.In this study, we examined the responses of various DDR pathways to CX-5461 treatment in primary aortic smooth muscle cells isolated from normal adult Sprague Dawley rats.We demonstrated that CX-5461-induced DDR was not associated with activations of the nucleotide excision repair, DNA mismatch repair, or the non-homologous end joining pathways, while the homologous recombination pathway was activated.

However, the alkaline comet assay did not show massive DNA double strand breaks in CX-5461-treated cells.Instead, CX-5461-induced DDR appeared to be related to induction of DNA replication stress, which was not attributable to increased formation of G-quadruplex or R-loop structures, but might be explained by the increased replication-transcription conflict.CX-5461-induced DDR was not exclusively confined to rDNA within the nucleolar compartment; the extra-nucleolar DDR might represent a distinct secondary response related to the downregulated Rad51 expression in CX-5461-treated cells.In summary, we suggest that DNA replication stress may be the primary molecular event leading to downstream ATM/ATR and p53 activations in CX-5461-treated vascular smooth muscle cells.

Our results provide further insights into the molecular basis of the beneficial effects of CX-5461 in proliferative Carriers vascular diseases.