Sequence-driven telomeric chromatin structure.

Interstitial (also called internal or intrachromosomal) telomeric sequences (ITS) are found in many organisms.(1) In hamsters, CHO cells show long (up to several Mbp) ITS(2) (Fig. 1A) which are over involved in spontaneous or radiation induced chromosome aberrations.(3) ITS are also found in human, but they are much shorter (several hundreds of bp maximum) and show no radiosensitivity.(4) We report here the striking observation that interstitial telomeric chromatin, although located near centromeres in hamster cells, shares common structural features with truly telomeric chromatin (located at the end of chromosomes), and notably a higher nucleosome density than bulk chromatin, which correlates with a highly regular chromatin structure. This study emphasizes the critical role of DNA in establishing particular chromatin folding, confirming that the DNA sequence encodes important information concerning local chromatin properties.