Fig. 3.

H2B_ub is induced in HeLa cells in response to complex DNA damage induced by high linear energy transfer (LET) α-particles and protons. (A-D) HeLa cells were untreated (designated C), irradiated with 10 Gy γ-irradiation, α-particles, or protons at low or high LET, and harvested at the time points indicated after ionizing radiation and purified histones analyzed by immunoblotting. In (E), cells were pretreated with dimethyl sulfoxide (DMSO) or actinomycin D before irradiation with 10 Gy high-LET protons. Red boxes indicate increased levels of H2B_ub. (B, D) Shown is the mean fold change ± standard deviation in H2B_ub normalized against H2B. *P < .05, **P < .01, ***P < .005, ****P < .002, as analyzed by a two-sample t test.