Abstract
As a ubiquitous phenomenon, DNA synthesis activity will be decreased after X-ray irradiation in living cells. However, we found that fibroblast cells derived from Gorlin (NBCCS) patients show increased levels of DNA synthesis after X-ray irradiation (Fujii et al., Biochem. Biophys. Res. Commun. 240, 269–272, 1997). Furthermore, the induction of DNA synthesis after irradiation was suggested to be caused by down-regulation of SUMO-3 gene expression (Mutat. Res. 578, 327-332, 2005). In the present study, after X-ray irradiation, the increase of DNA synthesis activity was also found in HeLa cells with knockdown of SUMO-3 by its special siRNA. Hereby, we can use HeLa cells, instead of NBCCS cells with very low capacity of growth. In order to investigate the cellular mechanisms underlying the down-regulation of SUMO-3, we performed proteomic analysis using Two-dimensional (2D) electrophoresis and mass spectrometry, and then searched for the proteins whose expression levels change early after X-ray irradiation in HeLa cells with knockdown of SUMO-3. As a result, expression levels of some candidate proteins were altered, and therefore the relationship between candidate proteins and DNA synthesis induction will be discussed.
