In vitro reconstitution and characterisation of structural and dynamic properties of telomeric chromatin

Abstract

Telomeres, the ends of all linear chromosomes, serve to protect and maintain chromosomal integrity by shielding against unwanted DNA damage responses. The mammalian telomere comprises a repetitive DNA sequence of TTAGGG that is densely packed as nucleosomes with a short NRL of ~157 bp. Despite the importance of the telomere, little is known about the structural and dynamic properties of the telomeric chromatin. In this study, we developed a versatile methodology to produce long telomeric DNA for the reconstitution of telomeric chromatin fibre in vitro. We showed that the telomere chromatin is characterised by heterogeneous nucleosome occupancy and nucleosome spacing due to the lack of nucleosome positioning information. In a compacted state, we observed a novel columnar feature with the telomeric array that is absent in the canonical ‘601’ array. Interestingly, TRF2, a telomere-binding protein, alone is sufficient to induce homogeneous compaction of the telomeric array with a columnar arrangement.