34. Phosrhorvlation Sites of NPAT bv CvclinE/ CDK2 Complex

Yasuharu Ninomiya, Kanae Hitomi* Akiyo Nishiyama, Masashi Sagara, Yoichi Taya *and Takashi Imai (*Natl. Cancer Center Research Institute)

Keywords: NPAT, phosphorylation, cyclin/CDK

We identified a housekeeping gene, the NPAT gene which is located 0.5kb from the 5' end of the ATM gene. As these two genes share the same promoter region, there is a possibility that the NPAT gene is also related to ATM functions such as genome stability, cellular responses to DNA damage or cell cycle control. Recently, Dr. Zhao shows that NPAT is a substrate of cycling/ CDK2 and NPAT plays a role in S-phase entry. To characterize the NPAT product in detail, we determined the modification sites of NPAT by cyc1inE/CDK2. The only carboxylterminal region of the NPAT was obviously phosphorylated by cycling/ CDK2 in vitro. We also found that other sites of NPAT were phosphorylated by other CDKs which were known to be active in S or G2/M phases of cell cycle. These results suggested that the NPAT functions at not only the G1 / S boundary, but also S and G2/M phases.