Ollivaud, S. | bioRxiv Science

bioRxiv2026

The role of the nuclear pore complex in the stability of disease-related short tandem DNA repeats

Nuclear pore complexes (NPCs) mediate selective transport between the nucleus and the cytoplasm, but also contribute to maintaining genome stability. Mutations in NPC genes cause genome instability and sensitivity to DNA damaging agents, and DNA that is difficult to repair or replicate relocates to NPCs, including expanded CAG repeats, which are associated with several neurological diseases. Here, we show that other disease-related short tandem repeats also relocate to NPCs. Relocation depends on the NPC basket protein Nup1, but is independent of the rest of the basket. Abrogating relocation to the NPC increases rates of repeat contraction, but not expansion. By contrast, deletion of the basket component NUP60, which causes mislocalization of all other basket proteins except Nup1, results in greater genome instability without affecting relocation to NPCs. Our results show that NPC association is a general feature of disease-related short tandem repeats, and suggest that relocation to NPCs is separable from the other genome maintenance functions of the NPC basket.

cell biology↗

bioRxiv2024

Interstitial telomeric sequences promote gross chromosomal rearrangement via multiple mechanisms

Telomeric DNA sequences are difficult to replicate. Replication forks frequently pause or stall at telomeres, which can lead to telomere truncation and dysfunction. In addition to being at chromosome ends, telomere repeats are also present at internal locations within chromosomes, known as interstitial telomeric sequences (ITSs). These sequences are unstable and prone to triggering gross chromosomal rearrangements (GCRs). In this study, we quantitatively examined the effect of ITSs on GCR rate in Saccharomyces cerevisiae using a genetic assay. We find that GCR rate increases exponentially with ITS length. This increase can be attributed to the telomere repeat binding protein Rap1 impeding DNA replication and a bias of repairing DNA breaks at or distal to the ITS via de novo telomere addition. Additionally, we performed a genome-wide screen for genes that modulate the rate of ITS-induced GCRs. We find that mutation of core components of the DNA replication machinery leads to an increase in GCRs, but many mutants known to increase GCR rate in the absence of an ITS do not significantly affect GCR rate when an ITS is present. We also identified genes that promote the formation of ITS-induced GCRs, including genes with roles in telomere maintenance, nucleotide excision repair, and transcription. Our work thus uncovers multiple mechanisms by which an ITS promotes GCR. Significance statementTelomeric DNA repeats are found at the ends of linear chromosomes where they, together with specialized proteins that bind to them, protect chromosome ends from degradation and unwanted DNA repair activities. Telomeric repeats can also be found at internal locations in the genome, where they are called interstitial telomeric sequences (ITSs). ITSs are prone to breakage and are associated with human diseases. In this study, using bakers yeast as a model organism, we show that instability at ITSs is driven by multiple factors, and identify genes that either promote or suppress gross chromosomal rearrangements induced by the presence of an ITS.

molecular biology↗