Upregulation of RAD51 by IR can be attenuated by berberine.

<p>(A), Radiation enhances RAD51 expression in tumor cells. Cells were exposed to the indicated doses of radiation and collected 24 h later for immunoblot analysis. (B), Change of RAD51 protein levels in response to berberine and radiation. Cells were pretreated with berberine (15 µM) for 24 h before being irradiated with 6 Gy of X-rays. Cells were collected for immunoblot analysis at 24 h after irradiation. (C), Inhibition of radiation-induced RAD51 foci formation by berberine. Shown are immunofluorescence images of KYSE30 and KYSE450 cells stained with anti-RAD51 antibody after 24 h of pretreatment with berberine and at 24 h after irradiation with 6 Gy of X-rays. DAPI counterstaining showed the nuclei. (D), <i>RAD51</i> mRNA levels after pretreatment with berberine (15 µM) for 24 h (KYSE30) or 48 h (KYSE450) before irradiation with 6 Gy. Cells were collected for quantitative real-time PCR analysis of the RAD51/GAPDH mRNA ratios at 24 h after exposure to 6 Gy of X-rays. Immunoblots and mRNA expression values are representative of at least two independent experiments.