| Summary: | 碩士 === 國立清華大學 === 分子與細胞生物研究所 === 104 === Metal-responsive transcription factor (MTF-1) regulates the expression of genes that modulates metal homeostasis and oxidative stress. MTF-1 is an essential regulatory factor for embryonic development of mammals. Owing to alternative splicing of the gene, several promyelocytic leukemia protein (PML) isoform can be found in the cells. PML is a well-known tumor suppressor involving in the induction of apoptosis, senescence and DNA repair. Reportedly, PML participates in the regulation of cellular antioxidative pathway and interacts with partner protein to modulate cellular activity. Previous studies indicate that SUMO modification of MTF-1 and PML can be altered by arsenic (As) treatment, we investigated whether PML and MTF-1 interacts and regulates cellular activity. We found that As induced the interaction between MTF-1 and PML in a dose- and time-dependent manner. This interaction does not occur for specific PML isoform, but for the PMLⅠto PMLⅥ. On the other hand, PML neither interacts with a specific domain of MTF-1. Mutation at the As binding residues of PML has also no effect on the interaction with MTF-1. Noticeably, the interaction was not stimulating by zinc or cadmium. Interestingly, the MTF-1/PML interaction does not alter the expression of MT2A gene, the major downstream target gene of MTF-1, or cell viability. MTF-1 interacted with PML mainly in cytosol. It is thus speculated that MTF-1 does not interact with PML nuclear body. The As-induced MTF-1/PML interaction can be reduced by decreasing cellular oxidative stress via administration of BHA, an antioxidant. Finally, we found that MTF-1 and PML synergistically decreased the level of reactive oxygen species (ROS). We conclude that cellular ROS level increases with the addition of As and stimulates the interaction between MTF-1 and PML. Concurrently, the interaction of MTF-1 and PML reduced cellular oxidative stress generated by As.
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