EB病毒BGLF4蛋白激酶及分子伴護蛋白DNAJB6對於病毒DNA引子酶進核調控及病毒溶裂期複製之探討

Regulation of nuclear targeting of EBV primase and viral lytic replication by EBV BGLF4 kinase and chaperone DNAJB6

何修宇(Hsiu-Yu He)

指導教授 ： 陳美如

國立臺灣大學/醫學院/微生物學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201903118

摘要

EB病毒屬於人類皰疹病毒的一員，感染了全球約95%的人口，不僅可能造成感染性單核球增多症，更與許多惡性腫瘤疾病擁有高度相關性。當受EB病毒感染時，大部分病毒會潛伏於體內，然而當病毒受到刺激時便會從潛伏期轉為溶裂期。此時EB病毒會開始複製DNA並表現大量的病毒基因。BGLF4是EB病毒唯一的蛋白激酶，先前已有許多研究指出BGLF4不只透過磷酸化不同的宿主以及病毒蛋白進而協助EB病毒的感染與複製，也促進數種本身不具有入核序列的病毒蛋白進入細胞核中協助病毒的複製，包括EB病毒引子酶BSLF1及DNA螺旋酶 (BBLF4) 等DNA複製複合體中的酵素。此外近來研究指出，分子伴護蛋白DNAJB6除了負責蛋白的摺疊以及運輸外，也被報導參與在數種病毒的複製過程中。因此我們在本篇研究中探討DNAJB6是否參與在BGLF4所調控的引子酶入核過程中，以及DNAJB6是否參與在EBV的複製過程。結果顯示在HeLa細胞中DNAJB6a與BGLF4皆可促進引子酶的進核，然而將在三者共同表現的系統中並未看見更加顯著的入核現象，而DNAJB6b則是會降低BGLF4將引子酶帶入細胞核的能力。在帶有EB病毒的上皮細胞株NA或淋巴球細胞株Akata中我們藉由即時定量聚合酶連鎖反應來檢測病毒DNA的表現，我們發現在shRNA剔弱DNAJB6a表現時會使EB病毒的複製效率以及病毒顆粒產生的總量下降。除此之外，我們也利用經過設計的嗎啉寡核苷酸，一種透過與特定RNA序列結合進而抑制基因表現的分子來抑制DNAJB6a的表現並觀察其對EB病毒的影響。結果顯示嗎啉寡核苷酸能確實剔弱DNAJB6a蛋白在Akata 細胞中的表現，也一同抑制了其餘EB病毒溶裂期蛋白的表現，進而抑制EB病毒的DNA複製效率以及病毒顆粒的產生。進一步我們想透過帶有EB病毒及綠色螢光蛋白的細胞設計能快速篩選對抗EB病毒或者對抗DNAJB6a的系統，初步結果顯示嗎啉寡核苷酸能降低綠色螢光蛋白的表現。綜合以上實驗結果，我們發現DNAJB6不只參與在引子酶的進核過程中，DNAJB6a更影響EB病毒DNA的複製以及病毒顆粒的產生。

關鍵字

BGLF4蛋白激酶 ； 分子伴護蛋白DNAJB6 ； 引子酶 ； 溶裂期複製 ； 嗎啉

並列摘要

Epstein-Barr virus, which is the first identified oncogenic virus, infects 95 % of human populations and is highly associated with several malignancies. During EBV lytic replication, EBV synthesizes viral DNA in the nucleus and expresses many viral genes for replication. BGLF4, as the only protein kinase encoded by EBV, phosphorylates several cellular and viral proteins to facilitate virus replication and maturation process. Previous studies showed that BGLF4 translocates into nucleus through interaction with nucleoporins; and BGLF4 induces the nuclear import of several non-NLS-containing EBV proteins, including EBV primase BSLF1 and DNA helicase BBLF4 within the DNA replication complex. Recent studies reported that DNAJB6, a member of Heat shock protein 40 (Hsp40), regulates the nuclear import of several viral proteins and facilitates viral replication. To reveal whether BGLF4 promotes the nuclear targeting of BSLF1 in a DNAJB6-dependent pathway, we did a transfection and knockdown assay in immunofluorescence assay and we found that the nuclear import ratio of BSLF1 was not significantly changed in DNAJB6a overexpression group, however the nuclear import of BSLF1 was decreased in DNAJB6b overexpression group. We then observed the viral DNA replication and found that knockdown of DNAJB6a decreased EBV replication and virion secretion in EBV-positive NA cells and Akata cells. In addition, we used Morpholino Mo-MRJ to target DNAJB6a and found Mopholino treatment reduced the cell growth and decreased EBV intracellular DNA and released virion DNA copy numbers. Moreover, EBV lytic protein expression was also suppressed, suggested that this molecule might exhibit anti-EBV potential. We also aimed to establish an anti-EBV drug screening system by AGS-BX1 and Akata-BX1 cells. We found that Morpholino treatment slightly decreased the GFP value in both cell lines. Taken together, DNAJB6a is involved in EBV primase nuclear import and EBV lytic replication.

並列關鍵字

BGLF4 protein kinase ； chaperone DNAJB6 ； primase ； lytic replication ； Morpholino

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