2018-08-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/713322摘要：PHRF1蛋白在N端具有對受質進行泛素化的Ring domain和可與甲基化組蛋白結合的PHD domain，Ｃ端則具有與RNA Pol II 最大次單元Rpb1作用的SRI domain，先前研究發現PHRF1透過泛素化TGIF可促進TGF-訊息傳遞；在小鼠模型中，PHRF1抑制急性骨髓性白血病(acute promyelocytic leukemia, APL)的生成，因PML-RAR重組蛋白與PHRF1競爭和TGIF結合的能力，進而阻斷TGF-訊息傳遞。我們先前實驗已證明PHRF1具有調節非同源末端黏合（non-homologous end-joining, NHEJ）的功能， PHRF1可連接二甲基化和三甲基化的組蛋白H3K36和Nbs1並對PARP1泛素化，使得PHRF1在DNA雙股斷裂時調控細胞的NHEJ。哺乳類生物體內經常性進行NHEJ的細胞為免疫細胞的可變異區進行V(D)J recombination和B細胞的固定區進行重鏈蛋白類型轉換（class-switch recombination, CSR）。 B細胞受到活化刺激時會在固定區進行免疫球蛋白類型轉換（class-switch recombination, CSR），原始的IgM轉換成為IgG, IgA和IgE等免疫球蛋白才能進行有效的體液性免疫作用，我們實驗的結果發現PHRF1在小鼠淋巴瘤細胞CH12F3-2A中會影響IgM轉換成IgA的效率，利用CD19-Cre小鼠特定表現在B淋巴球的特性製作了PHRF1基因剔除鼠，結果發現缺乏PHRF1表現的B淋巴球在LPS和IL-4刺激下所產生的IgG1和IgE明顯比對照組少，顯示缺少PHRF1會影響CSR的效率。 <br> Abstract: PHRF1 ubiquitinates substrates by RING domain and recognizes methylated histones via PHD domain. In addition, PHRF1 contains SRI domain to interact with Rpb1, the largest subunit of RNA Pol II complex. Previous reports show that PHRF1 promotes non-canonical TGF- signaling through TGIF ubiquitination and suppresses the formation of acute promyelocytic leukemia (APL) in mouse APL models. Recently, we report a new function of PHRF1 in modulating non-homologous end-joining (NHEJ). Ablation of PHRF1 decreases the NHEJ efficiency, while PHRF1 overexpression leads to an elevated NHEJ in H1299 reporter cells. PHRF1 mediates PARP1 polyubiquitination for proteasomal degradation. We propose that PHRF1 is a key factor to link H3K36 methylation and NBS1 to promote NHEJ upon DNA damage insults. In humans and mice, B cells consistently undergo NHEJ for the diversity of immune responses, V(D)J recombination and class-switch recombination (CSR), in response to stimulation. An effective immune response requires B cells to produce several classes of antibodies through class switch recombination (CSR) from IgM to become IgG, IgA, and IgE. Here, we present evidence that PHRF1 potentiates the efficiency of CSR. IgA switching was reduced in PHRF1-silenced CSR reporter CH12F3-2A cells. IgG1 and IgE switching was compromised in PHRF1 deficient B lymphocytes, indicating that the absence of PHRF1 impairs CSR to reduce antibody switching.PHRF1免疫球蛋白重鏈類型轉換Rpb1PHDPHRF1class switch recombinationRpb1PHD