50. Analysis of the Expression Pattern of the NPAT Gene after X-ray lrradiation

Yasuharu Ninomiya and Akiyo Nisiyama

Keywords: NPAT, ATM, X-ray irradiation

We identified the NPAT gene which shares a promoter with the ATM gene, and found the possibility that the NPAT gene, like the ATM gene, is also related to cellular responses to DNA damage or cell cycle control. We also confirmed that NPAT mRNA and protein expression peak at the G1/S stage and that NPAT is a substrate of cyclin E-CDK2, suggesting that NPAT plays a role in S-phase entry.

Then, to investigate the relationship between NPAT function and cellular responses to DNA damage, we studied the expression pattern of the NPAT gene after X-ray irradiation in human fibroblast cells.

We prepared RNA and protein from cultured cells synchronized by serum starvation after X-ray irradiation. The results of the analysis using the RNA and protein showed that the expression level of NPAT mRNA does not increase after X-ray irradiation, but the expression level of NPAT protein increases at 6 hours after X-ray irradiation. These results suggest that NPAT plays a role in cellular responses to DNA damage and the expression of the NPAT protein is regulated at post-transcriptional levels.

We are presently analyzing the function of the NPAT protein induced by X-ray irradiation.