TRAP150於mRNA降解的特性分析

Characterization of the role of TRAP150 in mRNA degradation

林庭安(Ting-An Lin)

指導教授 ： 譚婉玉

國立臺灣大學/醫學院/分子醫學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.10232

摘要

TRAP150起初被發現為轉錄活化複合體TRAP/Mediator的一個次單位。此外，TRAP150亦被發現為剪接體的其中一員，說明其可能在訊息核醣核酸剪接中扮演特定的角色。我們先前的研究指出，TRAP150可與其他剪接分子共同位於細胞核內的核斑點中，並活化剪接的過程。TRAP150可與完成剪接的訊息核醣核酸結合，並與數個外顯子接合複合體的組成蛋白及參與訊息核醣核酸運送出核的受器TAP有直接的交互作用。意料外地，當TRAP150被約束在先驅訊息核醣核酸的三端非轉譯區上時，可促進細胞核內此訊息核醣核酸的降解。我們試圖對TRAP150所引發的訊息核醣核酸的降解機制有更深入的了解。我們發現到不論TRAP150被指派到訊息核醣核酸五端的非轉譯區或是內含子上都能有促進訊息核醣核酸降解的效果，並且此作用似乎不依賴轉譯，顯示這並非典型的無意義誘導訊息核醣核酸降解的機制。另外，染色質免疫沉澱的實驗結果指出TRAP150座落在基因上的各個區域。由於它可與一些轉錄複合體的組成蛋白或參與訊息核醣核酸修飾的分子進行結合，因此，TRAP150可能會協調細胞核內核醣核酸處理過程的不同步驟，並使被異常加工的核醣核酸被降解。但TRAP150對於核內訊息核醣核酸修飾的確切作用仍需進一步的研究。

關鍵字

核醣核酸降解

並列摘要

TRAP150 has been identified as a subunit of the transcription regulatory complex TRAP/Mediator, and also a component of the spliceosome. TRAP150 contains an arginine/serine-rich domain and has sequence similarity with the cell death-promoting transcriptional repressor BCLAF1. My colleagues found that TRAP150 colocalizes with splicing factors in nuclear speckles and activates splicing in vivo. TRAP 150 remains associated with the spliced mRNA after splicing, and accordingly, it interacts with the integral exon-junction complex. Unexpectedly, when tethered to the 3’end of a precursor mRNA, TRAP150 can trigger mRNA degradation in the nucleus. However, unlike nonsense-mediated decay, TRAP150-mediated mRNA decay is irrespective of the presence of upstream stop codon and occurs in the nucleus. I attempted to understand more about the mechanism underlying TRAP150-mediated mRNA degradation. I found that TRAP150 induced mRNA degradation no matter whether it was tethered to the 5’-UTR, coding region, or intron, even for the mRNA lacking long open reading frames. Chromatin-immunoprecipitation showed that TRAP150 localized throughout the gene. Because TRAP150 interacted with several transcriptional complex and RNA processing factors, it may function in coordinating different steps of nuclear mRNA processing and perhaps target aberrantly processed mRNAs for degradation. How TRAP150 exactly acts in nuclear mRNA processing needs further studies.

並列關鍵字

TRAP150 ； mRNA degradation

參考文獻

1. Moore, M.J., From birth to death: the complex lives of eukaryotic mRNAs. Science, 2005. 309(5740): p. 1514-8.

2. de la Mata, M., et al., A slow RNA polymerase II affects alternative splicing in vivo. Mol Cell, 2003. 12(2): p. 525-32.

3. Howe, K.J., C.M. Kane, and M. Ares, Jr., Perturbation of transcription elongation influences the fidelity of internal exon inclusion in Saccharomyces cerevisiae. RNA, 2003. 9(8): p. 993-1006.

4. Cramer, P., D.A. Bushnell, and R.D. Kornberg, Structural basis of transcription: RNA polymerase II at 2.8 angstrom resolution. Science, 2001. 292(5523): p. 1863-76.

5. McCracken, S., et al., 5'-Capping enzymes are targeted to pre-mRNA by binding to the phosphorylated carboxy-terminal domain of RNA polymerase II. Genes Dev, 1997. 11(24): p. 3306-18.