| Summary: | 碩士 === 輔仁大學 === 營養科學系碩士班 === 101 === In epidemiological studies show that iron status was positively associated with breast cancer risk. Using tRNA microarray also demonstrated both of the expression nuclear (nuc)-encoded and mitochondrial (mt)-encoded tRNAs were upregulated in breast cancer cell and tissue. In addition, our previous study found iron deficiency was decreased the thio-modification of nuc-encoded Lys-tRNA(UUU), Glu-tRNA(UUC) and Arg-tRNA(UAU) in skeletal muscle tissue and cell culture, and that were associated with iron-sulfur cluster (ISC) biogenesis related protein. In this study, we investigate the effect of iron deficiency and hypoxia on expression and thio-modification of tRNAs, and the relationship between ISC biogenesis related protein and thio-modification of tRNAs in human breast cancer cell. The human MCF-7 breast cancer cell was treated with iron chelator deferoxamine (DFO) or cobaltous chloride (CoCl2) for mimicking iron depletion or hypoxia, respectively. Our results showed that treatment of 300 µM CoCl2 for 24 or 48h caused a declined in the level of thio-modification of nuc-encoded Lys-tRNA(UUU), Glu-tRNA(UUC) and Arg-tRNA(UCU). Similarly, the level of thio-modification of mt-encoded Lys-tRNA(UUU) and Glu-tRNA(UUC) were also decreased by treatment of CoCl2 for 24 or 48 h. In addition, the expression of nu-encoded Lys-tRNA(UUU) and mt-encoded Glu-tRNA(UUC) was decreased by treatment of CoCl2 for 48 h. However, the expression of the other nuc-encoded and mt-encoded tRNAs remained unchanged in CoCl2-treated cell. On the other hand, the level of thio-modification of nuc-encoded Lys-tRNA(UUU), Glu-tRNA(UUC), Arg-tRNA(UCU) and mt-encoded Glu-tRNA(UUC) were decreased by treatment with 50 µM DFO for 48h, however the level of thio-modification of mt-encoded Lys-tRNA(UUU) remained unchanged. The expression of nuc-encoded Arg-tRNA(UCU) and mt-encoded Glu-tRNA(UUC) were decreased by DFO treatment, but nuc-encoded Lys-tRNA(UUU) , Glu-tRNA(UUC) and mt-encoded Lys-tRNA(UUU) remained unchanged. On the other hand, the levels of total protein were decreased by treatment of CoCl2 and DFO for 24 or 48 h. The expression of mt-IscU protein was increased by treatment of CoCl2 for 48 h, but cyt-IscU and mt-IscS protein expression were unchanged. In contrast, the expression of cyt-IscU and mt IscS protein was increased by DFO treatment, but mt-IscU protein expression were unchanged. In summary, our results support the level of thio-modification of tRNAs were decreased by iron deficiency and hypoxia in breast cancer cell, and may not be associated with expression of tRNA and ISC biogenesis related protein. In addition, the levels of total protein were decreased by iron deficiency and hypoxia in breast cancer cell. The results suggested that the level of tRNA thio-modification were decreased by iron deficiency and hypoxia and affect protein synthesis in breast cancer cell.
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