Figure 4.

NAMPT S314 phosphorylation restores nuclear NAD, and facilitates DNA repair and cell survival. (a–d) Endogenous NAMPT-depleted HOK or HUVEC cells were stably expressed with shRNA-resistant (r) WT Flag-NAMPT or Flag-NAMPT S314A. Cells were treated with 10 Gy ionizing radiation. Nuclear NAD level was measured, and immunoprecipitates were performed using cell lysate 45 min after irradiation (a). The efficiency of the reactivation of reporter gene was measured 2 h after irradiation by luciferase assay (b). Cell viability was measured by BrdU incorporation assay 12 h after irradiation (c). HOK cell proliferation was measured by colony formation assay (d). IR, ionizing radiation; WCL, whole cell lysate; *p < 0.05; **p < 0.01; ***p < 0.001.