| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2001: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2000: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
We have isolated the newly discovered oncogenic protein gankyrin overexpressed in hepatocellular carinoma. Overexpression of gankyrin caused cellular transformation in NIH/3T3 cells, and led to increased phosphorylation of Rb and activation of E2F-1. Furthermore, gankyrin accelerated the degradation of Rb in vitro and in vivo. These results suggest that gankyrin is involved in Rb pathway and its overexpression contributes to hepatocarcinogenesis by inactivating and destabilizing Rb (Nature Medicine, 2000) (Alcohol Clin Exp Res, 2001). By binding with CDK4 kinase, gankyrin facilitates the phosphorylation of Rb. This binding competes with pl6 binding to CDK4 and counteracts the inhibitory function of p16INK4a. We demonstrate that gankyrin intetacts with S6 ATPase (Rpt3), a component of 19S regulatory subunit transiently (J Biol Chem, 2002). Besides Rb, another product of some tumor suppressor is readily degraded in case of gankyrin overexpression. This product doed not interaet with gankyrin in vitro or in vivo. Nevertheless, gankyrin attenuaees the posttranscriptional modification (phosphorylation, acetylation, and so on) of this product, and its intracellular sublocalization. We attempted to identify the other binding partners of gankyrin, using the yeast two hybrid method. 0ne candidate inhibits the anchorage independent cell growth by gankyrin overexpression. Whereas the mechanism and importance of the correlation between gankyrin and this protein are yet to be elucidated, a part of this protein induces the proapoptotic activity to gankyrin-overexpressing cell lines. Furthermore, to achieve high transgene expression in hepatoma cell lines for human gene therapy, we investigated which promoter regions are involved in it (Gene therapy, 2002). We will investigate whether these peptides counteract the oncogenic function of gankyrin specifically.
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