TSA can downregulate Eps8 expression and inhibit v-Src-induced transformation

• Main Authors: Shiuh-Hwa Yeh, 葉旭華
• Other Authors: Ming-Chei Maa
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/32759845945740831247

碩士 === 中山醫學院 === 生物化學研究所 === 89 === Eps8 is a recently identified substrate of the epidermal growth factor receptor (EGFR). Its overexpression can enhance EGFR-mediated mitogenesis in different cells. Eps8 can be efficiently phosphorylated by several other receptor tyrosine kinases (RTKs). Previous studies have indicated that Src can also phosphorylate Eps8 both in vitro and in vivo. Constitutive phosphorylation of Eps8 was detected in many tumor cell lines. Further studies have indicated that Eps8 is an oncoprotein and can promote tumor formation. The dynamics of chromatin folding is important for the regulation of gene expression. Histone acetylase (HAT) and histone deacetylase (HDAC) are two crucial components determining the acetylation of histone that is supposed to regulate the chromatin structure and transcription activity. Previous studies have reported that Trichostatin A (TSA), a Streptomyces product, is as an antifungal antibiotic. TSA was found to cause the induction of Friend leukemia cell differentiation and specific inhibition of the cell cycle of normal rat fibroblasts at very low concentration. Several further studies have demonstrated that TSA can cause the morphological reversion of transformed cells. Accumulating evidence has suggested that it is a potent, specific inhibitor of HDAC. To study the effect of TSA to v-Src transformed cells (IV5), we treated IV5 cells with or without TSA and observed that TSA could effectively inhibit the growth of IV5 cells. In addition, TSA could abrogate the ability of IV5 cells to form colonies in soft agar. Interestingly, we found that TSA could downregulate the expression of Eps8, but the amount and kinase activity of v-Src were not affected. Furthermore, removal of TSA from 24 hr treated culture could restore the expression of Eps8. RT-PCR and Northern blotting analysis of the abundance of eps8 mRNA revealed the significant reduction of eps8 transcript in TSA-treated IV5 cells relative to control. Since overexpression of Eps8 can enhance the mitogenic signaling of EGFR and cause cellular transformation. Our results implicated the TSA- repressed Eps8 expression might attribute to TSA-induced reversion of v-Src transformed cells. Albeit the mechanisms of eps8 transcriptional regulation in TSA-treated v-Src transformed cells are still unknown, it is deserved to further investigate and identify the TSA- responsive elements in eps8 promoter and their binding transcriptional factors in our future study.