Biological Macromolecules Laboratory (Maeshima Group)

Pyrrole–imidazole (PI) polyamides bind to the minor groove of DNA in a sequence-specific manner without causing denaturation of DNA. To visualize telomeres specifically, tandem hairpin PI polyamides conjugated with a fluorescent dye have been synthesized, but the study of telomeres using these PI polyamides has not been reported because of difficulties synthesizing these tandem hairpin PI polyamides. To synthesize tandem hairpin polyamides more easily, we have developed new PI polyamide fragments and have used them as units in Fmoc solid-phase peptide synthesis. Using this new method, we synthesized four fluorescent polyamide probes for the human telomeric repeat TTAGGG. The polyamides synthesized using the new method successfully targeted to human and mouse telomeres under a physiological condition and allow easier labeling of telomeres in the cells while maintaining the telomere structure. Using the fluorescent polyamides, we demonstrated that the telomere length at a single telomere level is related to the abundance of TRF1 protein, a shelterin complex component in the telomere.

Left, schematic representation showing that TH59 compound with a fluorescent dye binds to the human telomere sequence (TTAGGG repeat). Right, the telomere regions of chromosome ends are labeled with TH59 (green).　DNA stain (blue).

– Entrez PubMed

Press release

Genomic DNA is three-dimensionally organized into the nucleus, and is thought to form compact chromatin domains. Although chromatin compaction is known to be essential for mitosis, whether it confers other advantages, particularly in interphase cells, remains unknown. Here, we report that chromatin compaction protects genomic DNA from radiation damage. Using a newly developed solid-phase system, we found that the frequency of double-strand breaks (DSBs) in compact chromatin after ionizing irradiation was 5-50-fold lower than in decondensed chromatin. Since radical scavengers inhibited DSB induction in the decondensed chromatin, the condensed chromatin had a lower level of reactive radical generation after ionizing irradiation. We show that chromatin compaction also protects DNA from attack by chemical agents. Our findings suggest that genomic DNA compaction plays an important role in maintaining genomic integrity.