| Summary: | 碩士 === 國立臺灣大學 === 生化科學研究所 === 101 === Human Puf-A (hPuf-A) is a novel member of the RNA-binding protein, Puf family which regulates mRNA translation and decay. Computer modeling reveals that hPuf-A contains 6 Puf repeats instead of the 8-repeat Puf repeat domain and is structurally distinct from the canonical Puf proteins. In the previous study, we discovered that hPuf-A translocates from the nucleolus to the nucleoplasm upon genotoxic stress to prevent PARP-1 from caspases cleavage and degradation, thus promotes cell viability. However, the physiological functions of hPuf-A are still remained many to be discovered. In this study, we investigated the role of hPuf-A in promotion of breast cancer tumorigenesis. The immunohistochemical stainings of breast cancer specimens with clinical stage of Ductal carcinoma in situ (DCIS), stage I, II, III, IV showed that hPuf-A was upregulated in tumors with more advanced clinical stage. The expression levels of hPuf-A were significantly correlated with the clinical stage progression (P=0.005). Silencing the endogenous hPuf-A expression reduced the colony forming ability of MDA-MB-231 and T47D breast cancer cells. By contrast, overexpression of hPuf-A in MDA-MB-231 cells led to enhanced colony formation and colony size. Xenograft assays by subcutaneous injection of hPuf-A-silenced and hPuf-A overexpressing MDA-MB-231 cells into nude mice further demonstrated the tumorigenicity of hPuf-A. Interestingly, the silence of hPuf-A resulted in reduced expressions of DDX3 and RbAp48. The reduced expressions of DDX3 and RbAp48 might be regulated by the association of hPuf-A with DDX3 and RbAp48 mRNAs. Besides, the next generation sequencing revealed new potential mRNA targets of hPuf-A, and many of them belong to ribosomal proteins.
Overall, our results indicated that the upregulation of hPuf-A promotes breast cancer tumorigenesis. The underlying mechanism might be the regulation of hPuf-A to its associated mRNAs, which are DDX3 and RbAp48.
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