| Summary: | 碩士 === 國立陽明大學 === 生化暨分子生物研究所 === 95 === p53 tumor suppressor which is important in maintaining the genomic stability is the most frequently mutated gene in human cancers. Upon DNA damage, p53 is activated and accumulated in the nucleus. As a transcription factor, it trans-activates downstream targets involved in cell survival, cell cycle arrest or apoptosis.
We have previously identified Rad (Ras-related associated with diabetes) as a p53 activated and DNA damage inducible gene whose overexpression suppressed cell growth. To further examine the biological function of Rad, we have established H1299 clones stably expressing Rad and observed that the cells exhibited decreased growth rates. Increased apoptosis was found in H1299 cells transiently transfected with Rad, whereas the fraction of apoptotic cells decreased in the Rad-knockdown A549 cells undergoing DNA damage.
Rad has been shown to bind and inhibit the Rho-associated kinase (ROCK). We show that similar to ROCK inhibitor Y27632, Rad could inhibit the phosphorylation of cofilin, which is a downstream target of ROCK/LIMK signaling involved in actin polymerization. In addition, wound healing assay also revealed that H1299 cells stably expressing Rad exhibited increased migration ability.
Together our results show that expression of Rad inhibits cell growth and induces apoptosis. Consistent with its inhibition in cofilin phosphorylation, Rad alters cell morphology and increases migration of cells, suggesting that p53 may be involved in morphological signaling in addition to its roles in growth/apoptosis regulation by activating Rad expression.
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