CTCF

位於16號人類染色體的基因

轉錄阻抑物CTCF,也被稱為11鋅指蛋白或CCCTC結合因子,是由人類CTCF基因編碼的轉錄因子[1][2]。CTCF參與多個細胞進程,包括轉錄調控、絕緣子活性調控、V(D)J重組、染色質結構調控等[3][4]

CCCTC-結合因子(鋅指蛋白)
PDB rendering based on 1x6h.
有效結構
PDB 直系同源檢索:PDBe, RCSB
標識
代號 CTCF
擴展標識 遺傳學604167 鼠基因109447 同源基因4786 GeneCards: CTCF Gene
RNA表現模式
更多表現資料
直系同源體
物種 人類 小鼠
Entrez 10664 13018
Ensembl ENSG00000102974 ENSMUSG00000005698
UniProt P49711 Q61164
mRNA序列 NM_001191022 NM_181322
蛋白序列 NP_001177951 NP_851839
基因位置 Chr 16:
67.6 – 67.67 Mb
Chr 8:
105.64 – 105.68 Mb
PubMed查詢 [1] [2]

發現

CTCF最早被認為在雞體內抑制c-myc基因表現。CTCF蛋白和以CCCTC為核心序列的三個規則間隔重複蛋白相結合,故得名CCCTC結合因子[5]

功能

CTCF的主要功能是調控染色質的3D結構[4]。CTCF和DNA雙鏈結合形成染色質環,並把DNA錨定在細胞結構上(例如核纖層)[6]。此外,CTCF還能充當常染色質和異染色質的邊界。

DNA的3D結構會影響基因的調控,因此CTCF的活性會影響基因表現。絕緣子能阻礙強化子和啟動子的結合,而CTCF是絕緣子的主要活性部分[5]

已觀測到的活性

CTCF的結合有多種效應。目前尚不能確定下列功能是直接由CTCF導致。

轉錄調控

CTCF對於IGF2的抑制起重要作用。具體機制為CTCF和H19基因的基因銘印(ICR)區域、差異甲基化區域-1(DMR-1)和MAR3區域結合[7]

絕緣子

CTCF能通過和目標區域結合以阻礙強化子和啟動子的相互作用,從而降低強化子對某些功能域的調控能力[8]。除此之外,CTCF還能作為染色質「路障」,阻止異染色質的進一步形成。

染色質結構調控

CTCF往往以二聚體的形式存在,這會導致DNA形成環狀結構。CTCF也經常在DNA和核纖層的結合處出現。使用ChIP-seq技術可以發現CTCF同黏連蛋白一起在基因組內廣泛存在,並對染色質的高級結構起調節作用[9][10][11]

RNA剪切調控

CTCF對mRNA剪切有調控作用[12]

與DNA結合

CTCF和共有序列CCGCGNGGNGGCAG相結合。這條序列在其結構域中有11個鋅指結構。CTCF和基因的結合被CpG的甲基化所影響[13][14]

CTCF在19個細胞系中大約有55000個共同的DNA結合位點(共77811個獨特位點)。CTCF能和不同的鋅指結構結合,這讓它的功能非常多樣化。大約有30000個CTCF的位點功能已經被定義。在人類的不同細胞中大約有15000-40000個CTCF結合位點。除此之外,高解析度的核小體比對現實CTCF的不同結合位點可能和核小體的定位有關[15][16][17][18]

蛋白互作

CTCF可能和Y box結合蛋白1有相互作用[19]。黏連蛋白對CTCF形成的環狀結構有穩定作用[20]

參考

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  9. ^ Yusufzai, Timur M.; Tagami, Hideaki; Nakatani, Yoshihiro; Felsenfeld, Gary. CTCF tethers an insulator to subnuclear sites, suggesting shared insulator mechanisms across species. Molecular Cell. 2004-01-30, 13 (2): 291–298 [2018-10-01]. ISSN 1097-2765. PMID 14759373. (原始內容存檔於2018-10-02). 
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