Secondary structure alterations of histones H2A and H2B in X-irradiated human cancer cells; Altered histones persist in cells for at least 24 hours

Izumi, Yudai; Yamamoto, Satoshi*; Fujii, Kentaro; Yokoya, Akinari

We measured and compared the circular dichroism (CD) spectra and secondary structures of histone proteins H2A, H2B, and their variants extracted from X-irradiated and unirradiated human HeLa cells. Compared to unirradiated cells, a relative increase in -helix structure and decrease in other secondary structures was observed in X-irradiated cells. These structural alterations persisted for at least 24 hours, which is substantially longer than the 2 hours generally known to be required for DNA double strand break repair.