【摘要】：轉(zhuǎn)錄抑制因子Bcl6對(duì)B細(xì)胞生發(fā)中心的發(fā)育和功能維持起著重要的作用,Bcl6的表達(dá)失控將會(huì)直接導(dǎo)致B細(xì)胞淋巴瘤的產(chǎn)生,因此如何精確調(diào)控Bcl6在生發(fā)中心中的表達(dá)對(duì)于預(yù)防由生發(fā)中心引發(fā)的疾病有著重要的意義。大量的研究揭示了 Bcl6的轉(zhuǎn)錄水平調(diào)控,然而關(guān)于Bcl6蛋白翻譯后的修飾卻鮮為人知。本文中,我們發(fā)現(xiàn)了近年來(lái)被廣泛報(bào)道的一種重要的腫瘤抑制因子Fbw7,通過(guò)形成SCFFbw7復(fù)合體介導(dǎo)Bcl6蛋白的降解,從而控制細(xì)胞內(nèi)Bcl6蛋白穩(wěn)定性。在本文的研究中,我們通過(guò)生物信息學(xué)的方法,對(duì)Fbw7的底物進(jìn)行預(yù)測(cè),我們發(fā)現(xiàn)Bcl6中包含了Fbw7直接識(shí)別的降解信號(hào)序列,且該段序列在不同物種中高度保守。接下來(lái),我們利用生物化學(xué)與分子生物學(xué)等技術(shù)手段,通過(guò)一系列外源和內(nèi)源的實(shí)驗(yàn)驗(yàn)證了 Fbw7能夠結(jié)合Bcl6并介導(dǎo)其泛素化降解,此外,我們還發(fā)現(xiàn)Bcl6的降解依賴于磷酸激酶JNK對(duì)其磷酸化。最后,我們進(jìn)一步探究了Fbw7介導(dǎo)Bcl6降解的生理意義,我們首先發(fā)現(xiàn)Fbw7在生發(fā)中心B細(xì)胞中高表達(dá),當(dāng)在生發(fā)中心中特異性敲除Fbw7基因后,我們觀察到生發(fā)中心b細(xì)胞的發(fā)育并未受到影響,然而其抗體類(lèi)型轉(zhuǎn)換能力卻顯著受損。初步實(shí)驗(yàn)結(jié)果發(fā)現(xiàn)Fbw7敲除后,生發(fā)中心中記憶細(xì)胞的比例上調(diào),這可能是Bcl6蛋白水平的上調(diào)抑制了 blimpl蛋白,從而導(dǎo)致生發(fā)中心b細(xì)胞向記憶細(xì)胞分化。綜上所述,我們的研究發(fā)現(xiàn)了 Fbw7通過(guò)介導(dǎo)Bcl6的降解,影響生發(fā)中心B細(xì)胞向記憶細(xì)胞的分化來(lái)實(shí)現(xiàn)對(duì)生發(fā)中心的調(diào)控。
[Abstract]:Transcription suppressor Bcl6 plays an important role in the development and functional maintenance of germinal center of B cells. The uncontrolled expression of Bcl6 will directly lead to the production of B cell lymphoma. Therefore, how to accurately regulate the expression of Bcl6 in germinal centers is of great significance for the prevention of germinal center-induced diseases. A large number of studies have revealed the transcriptional regulation of Bcl6, but little is known about post-translational modification of Bcl6 proteins. In this paper, we have found that Fbw7, an important tumor suppressor, has been widely reported in recent years to control the stability of Bcl6 protein by forming SCFFbw7 complex to mediate the degradation of Bcl6 protein. In this study, we predicted the substrate of Fbw7 by bioinformatics. We found that Bcl6 contains degradation signal sequence recognized directly by Fbw7, and this sequence is highly conserved in different species. Then, by means of biochemistry and molecular biology, we proved that Fbw7 can bind to Bcl6 and mediate its ubiquitin degradation through a series of exogenous and endogenous experiments. We also found that Bcl6 degradation depends on phosphorylation of phosphokinase JNK. Finally, we further explored the physiological significance of Bcl6 degradation mediated by Fbw7. We first found that Fbw7 is highly expressed in germinal center B cells, and when Fbw7 gene is specifically knocked out in germinal center, We observed that the development of germinal center b cells was not affected, but the ability of antibody type conversion was significantly impaired. The preliminary results showed that the proportion of memory cells in germinal center increased after Fbw7 knockout. This may be because the up-regulation of Bcl6 protein level inhibited blimpl protein, which led to the differentiation of germinal center b cells into memory cells. In conclusion, we found that Fbw7 regulates germinal center by mediating the degradation of Bcl6 and affecting the differentiation of germinal center B cells into memory cells.
【學(xué)位授予單位】：華東師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：Q78

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