Characterisation of p21 foci at heavy ion induced DNA lesions

The cyclin-dependent kinase inhibitor p21 is involved in a variety of different cellular processes, like cell cycle control, senescence and terminal differentiation. Recently, p21 was found to localize to discrete sites of DNA damage induced by heavy ions [1]. To investigate the functional significance of p21 at the DNA lesions, we designed a mammalian expression construct encoding translational fusions of human p21 to an enhanced green fluorescent protein (EGFP). HeLa cells transiently transfected with this construct were irradiated with low energy krypton ions to test the ability of the p21 fusion protein to form ionizing radiation induced foci (IRIF) at sites of ion traversals (Fig. 1).