| Summary: | 碩士 === 慈濟大學 === 分子生物及細胞生物研究所 === 94 === Human securin, also called PTTG1 (pituitary tumor transforming gene 1) plays an important role in sister chromatid separation during mitosis. At the interphase it binds to separase. When cells go into metaphase anaphase promoting complex (APC) is activated to degrade securin, releasing separin, which cleaves cohesin resulted in the separation of sister chromatids. When the securin is overexpressed it can transform cells and promote tumor metastasis. Thus securin appears to be a multi-function protein. It can also act as transcription co-activator and modulate gene activation presumably involving in either transformation or tumor metastasis. Thus its functions may depend on which protein it associated with. Previously using yeast two hybrid screen, we have identified zyxin, estrogen related receptor alpha (ERRA), and COPS5 that interact with securin. ERRA can bind to regulator sequence of Osteopontin (OPN), and stimulate mouse OPN expression. It is likely that the migration of tumor cell may be modulated by interaction between securin and ERRA.
OPN is a glyco-phosphoprotein that is expressed and secreted by numerous human cancers. It functions in cell adhesion, chemotaxis, prevention of apoptosis, and anchorage-independent growth of tumor cells by regulating cell–matrix interactions and cellular signaling through binding with integrin and CD44 receptors.
In order to unravel the interaction of securin and ERRA, and its implication in cell motility, first, we carried out pull down assay and IP/Western to demonstrate that ERRA interacts specifically with securin both in vitro and in vivo. Then using truncated securin and ERRA to map at which domain they interact, and analyzed whether securin and ERRA could cooperate to modulated OPN expression by luciferase reporter assay. In the future we will transfect GFP/securin fusion constructs or ERRA constructs into cell, using confocal microscopy to identify their relation and accumulation, during different phases of cell cycle, and between metastasis and non-metastasis cancer cell.
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