Visualization of the dynamic interaction between nucleosomal histone H3K9 tri-methylation and HP1a chromodomain in living cells

Histone lysine methylation is an epigenetic mark that can control gene expression. In particular, H3K9me3 contributes to transcriptional repression by regulating chromatin structure. Successful mitotic progression requires correct timing of chromatin structure changes, including epigenetic marks. However, spatiotem-poral information on histone modifications in living cells remains limited. In this study, we created an FRET-based probe for live-cell imaging based on the HP1a chromodomain (HP1aCD), which binds to H3K9me3. The probe was incorporated into chromatin and the emission ratio decreased after treatment with histone methyltransferase inhibitors, indicating that it successfully traced dynamic changes in H3K9me3. Upon entry into mitosis, the probe???s emission ratio transiently increased with a concomitant in-crease in H3K9me3, then exhibited a stepwise decrease, probably due to loss of HP1aCD binding caused by phosphorylation of H3S10 and demethylation of H3K9me3. This probe will be a useful tool for detecting dynamic changes in chromatin structure associated with HP1a.

Automated summary

This study developed an FRET-based probe that successfully traces dynamic changes in H3K9me3 and revealed subtle alterations that occur during mitosis.