EB病毒的Rta蛋白質對TATA-less啟動子轉錄活性的調控

Activation of TATA-less promoters by Rta of Epstein-Barr virus

楊永政(Yung-Cheng Yang)

指導教授 ： 曾昭能

高雄醫學大學/生命科學院/生物醫學暨環境生物學研究所/碩士(2007年)

https://doi.org/10.6832/KMU.2007.00132

摘要

中文摘要
基因要轉錄出mRNA必須透過RNA polymerase II的作用，而TATA-less啟動子的轉錄起始已知是由TFIID與Sp1結合在GC box序列而引發的，其中TFIID是一個多分子組成的複合體，其組成包含了TAFII250, TAFII150及TAFII130與結合在啟動子GC區域上的Sp1。EB病毒 (Epstein-Barr virus) 含有兩個生活史，當病毒感染B淋巴細胞之後通常以潛伏型態存在，然而，EB病毒的增生必須透過溶裂循環，在宿主細胞受到一些特定的化學或是物理刺激後，能刺激病毒引發溶裂循環，當EB病毒進入溶裂循環，EB病毒會表現Rta及Zta兩種轉錄因子，分別是由BRLF1與BZLF1基因所轉譯出來。目前已知Rta不僅會結合到啟動子上的RRE序列來活化基因轉錄，也會間接的與Sp1結合，以共同活化子的身分來增進基因的轉錄活性。本篇研究目的主要是在探討Rta是否會藉由與TAFII130結合來活化缺乏TATA序列的啟動子的表現。首先利用DNA affinity precipitation assay與染色體免疫沉澱分析(chromatin immunoprecipitation analysis)發現Rta會與TAFII130及Sp1蛋白質形成複合體結合在EB病毒的LMP1基因與BALF5基因的TATA-less啟動子上，並更進一步的觀察到Rta與TAFII130間有交互作用，並會聚集在細胞核中，此外，結合區域分析也證實了Rta是透過TAFII130的C端部份與TAFII130結合，最後，Rta也可以活化LMP1、BALF5及人類androgen receptor等三個TATA-less啟動子的轉錄活性達9-17倍。綜合以上結論，這個研究證實了Rta可以透過與TAFII130與Sp1的結合來活化TATA-less啟動子的表現。

關鍵字

病毒 ； 啟動子 ； 轉錄活性

並列摘要

Abstract
In eukaryotes, gene encoding mRNA are transcribed by RNA polymerase II, a multiprotein enzyme. Initiation of TATA-less promotes has been involved in binding of the TFIID, including TAFII250, TAFII150, and TAFII110, with Sp1 bound at the GC boxes. Epstein-Barr virus (EBV) has two distinct life cycles. EBV is normally maintained under latent conditions after infecting B lymphocytes. However, EBV must enter a lytic cycle to proliferate. The lytic cycle can be activated in vitro by treating the cell with chemicals or physical stimulus. When EBV enters the lytic cycle, the virus expresses two transcription factors, Rta and Zta, which are encoded by BRLF1 and BZLF1, respectively. Rta not only binds to RRE in promoters to activate transcription but also indirectly interacts with Sp1 as a coactivator to enhance the transcription that depends on Sp1. The aim of this work is to demonstrate whether Rta activates TATA-less promoters via an interaction with TAFII130. By using DNA affinity precipitation assay and chromatin immunoprecipitation analysis, the Rta-TAFII130-Sp1 complex binds to the Sp1 sites on the TATA-less promoters of LMP1 and BALF5 of EBV. Moreover, Rta interacts and colocalizes with TAFII130 in the nucleus. In addition, binding domain analysis shows that Rta interacts with the C-terminal region of TAFII130. Finally, Rta transactivates three TATA-less promoters including LMP1、BALF5 and human androgen receptor by a factor 9-17. Taken together, this study reveals that Rta activates TATA-less promoters through an interaction with TAFII130 and Sp1.

並列關鍵字

Rta ； Epstein-Barr virus ； EBV ； TATA-less promoters

參考文獻

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