The Shelterin-chromatin interplay in telomere homeostasis and genome stability

The linear ends of eukaryotic chromosomes are formed by telomeres, nucleoprotein structures containing double-stranded TTAGGG repeats, ending in a single-stranded DNA 3-overhang. In mammalian cells, the six-subunits Shelterin complex binds telomeres and is critical for telomere homeostasis. Shelterin ensures faithful replication of telomeric DNA, hides linear ends in a looped structure to prevent their recognition as DNA breaks and ensures control over telomere length. Telomeres are packed into nucleosomes, and therefore Shelterin binds in a chromatin context. Interactions between individual Shelterin subunits and nucleosomes have been investigated in vitro, as well as their impact on chromatin organisation. Despite increasing evidence of a Shelterin-chromatin interplay, many questions remain unanswered. The dynamics, affinities and consequences of full Shelterin complex binding to chromatin are unknown. I will employ single-molecule experiments with optical tweezers and bulk assays to monitor the binding of Shelterin on telomeric chromatin and its impact on nucleosomes (and vice versa). The physiological role of this interplay, as well as its regulation, is also largely unknown. I will investigate the impact of an impaired Shelterin-chromatin interaction on telomere and genome stability, as well as its impact on the telomeric proteome and the epigenetic landscape of telomeres. Lastly, I will examine how the Shelterin-chromatin interaction is regulated during the cell cycle. Altogether, this work will provide fundamental new knowledge on Shelterin recruitment and functions at telomeres. Considering that in recent years Shelterin gained interest as an anti-cancer therapeutic target, this basic knowledge has the potential to guide future research aimed at targeting Shelterin for induction of telomeres dysfunction in cancer cells.