Expanding the tools to interfere with telomere regulation through epigenetic, new small ligands and AsiDNA

Interfering with telomere regulation has a double interest: on the one hand, it is an approach to gain insight into telomere regulation; on the other hand, it is a potential approach against proliferation of tumour cells. The main results of our studies on this topic are outlined here below.

The figure here below synthetises our major results, detailed below.

Interfering with telomeres: epigenetic and ligands

Credits

©P. Alberti

Epigenetic. Chromosome ends are transcribed into long non-coding “telomeric repeat-containing RNA” (TERRA) that contribute to telomere regulation. TERRA transcription starts in the subtelomeric regions. In order to study the epigenetic regulation of TERRA expression, we used CRISPR/dCas9 to target a DNA demethylase to subtelomeric CpG islands in TERRA promoters in a human cell line. We found that the targeted demethylation resulted in an NRF1-dependent increase in TERRA expression (doi: 10.3390/ijms20112791).

G4 ligands and ligands of the telomeric duplex-G4 junction. G4 ligands are useful tools to study telomere regulation and potential anticancer agents. We conceived and synthetized a dimeric G4 ligand (360A)2A, composed of two G4 ligand moieties. We showed that, in vitro, it interfered with the binding of RPA to telomeres more efficiently than its single moiety counterpart 360A: by stabilising contiguous G4, (360A)2A impaired the binding of RPA to a telomeric G-strand and also displaced RPA from a telomeric G-strand (doi: 10.1039/c7cc07048a).

We also designed and synthetized ligands of the telomeric duplex/G4 junction, composed of a minor groove binder recognizing the telomeric duplex sequence and of a G4 ligand (Pauline Lejault’s PhD thesis).

We used Single Telomere Length analysis (STELA) to study the impact of G4 ligands on the length of telomeres at single-telomere resolution. We showed, for the first time, that G4 ligands can induce rare telomere deletion events (TDE) in cells. The frequency of TDE was slightly higher in cells treated with (360A)2A compared to cells treated with 360A (doi: 10.3390/molecules24030577).

AsiDNA. Too short telomeres can undergo aberrant repair leading to telomere fusions and thus contributing to genome instability. AsiDNA are DNA molecules that mimic a DNA double strand break (DSB) and hijacks the recruitment of proteins involved in DNA repair pathways. We showed that AsiDNA decreased the frequency of telomere fusions in a model cancer cell line which mimics a crisis-like state characterized by telomere fusions (doi: 10.1093/hmg/ddab008).

Interfering with telomeres: AsiDNA

Credits

©: P. Alberti