G-四聯體

G-四聯體（英語：G-quadruplex、G-tetrads或G₄-DNA）是一種由富含鳥嘌呤的核酸序列所構成的四股型態。含有經由胡斯坦(Hoogsteen)氫鍵維持穩定，並由鳥嘌呤以正方形方式排列而成的結構。在方形中央有一個單價陽離子（通常是鉀）^[1]。這種結構可見於DNA、RNA、LNA（鎖核酸）與PNA（肽核酸）；根據形成四聯體的各股的方向，可能有分子內（intramolecular）、雙分子（bimolecular）或四分子（tetramolecular）等不同類型^[2]。

在四聯體的結構中，我們可以根據四股的方向，將結構分為平行和反平行（英語：Antiparallel (biochemistry)）。

Structure of a G-quadruplex. Left: a G-tetrad. Right: an intramolecular G-quadruplex

3D Structure of the intramolecular human telomeric G-quadruplex in potassium solution (PDB ID 2HY9). The backbone is represented by a tube. The center of this structure contains three layers of G-tetrads. The hydrogen bonds in these layers are represented by blue dashed lines.

註釋

1. Campbell, Nancy H.; Neidle, Stephen. Chapter 4. G-Quadruplexes and Metal Ions. Astrid Sigel, Helmut Sigel and Roland K. O. Sigel (編). Interplay between Metal Ions and Nucleic Acids. Metal Ions in Life Sciences 10. Springer. 2012: 119–1134. doi:10.1007/978-94-007-2172-2_4.
2. Bochman, Matthew L.; Paeschke, Katrin; Zakian, Virginia A. DNA secondary structures: stability and function of G-quadruplex structures. Nature Reviews Genetics 13. Nature Publishing Group. 2012: 770–780. doi:10.1038/nrg3296.

參考文獻

• Jiangtao Ren, Jiahai Wang* , Lei Han, Erkang Wang*, Jin Wang*. Kinetically grafting G-qaudruplex onto DNA nanostructure as structure and function encoding via DNA machine. Chem. Commun. 2011, 47: 10563–10565 [2015-06-19]. （原始內容存檔於2015-04-20）.
• Johnson JE, Smith JS, Kozak ML, Johnson FB. In vivo veritas: using yeast to probe the biological functions of G-quadruplexes. Biochimie. 2008, 90 (8): 1250–1263 [2015-06-19]. PMC 2585026 . PMID 18331848. doi:10.1016/j.biochi.2008.02.013. （原始內容存檔於2019-02-07）.
• Huppert JL and Balasubramanian S. Prevalence of quadruplexes in the human genome. NAR. 2005, 33 (9): 2908–2916 [2007-06-20]. PMC 1140081 . PMID 15914667. doi:10.1093/nar/gki609. （原始內容存檔於2007-05-06）.
• Todd AK, Johnston M, Neidle S. Highly prevalent putative quadruplex sequence motifs in human DNA. NAR. 2005, 33 (9): 2901–2907 [2007-06-20]. PMC 1140077 . PMID 15914666. doi:10.1093/nar/gki553. （原始內容存檔於2007-05-06）.
• Burge S, Parkinson GN, Hazel P, Todd AK, Neidle S. Quadruplex DNA: sequence, topology and structure. NAR. 2006, 34 (19): 5402–5415 [2007-06-20]. PMC 1636468 . PMID 17012276. doi:10.1093/nar/gkl655. （原始內容存檔於2008-10-07）.
• Siddiqui-Jain A, Grand CL, Bearss DJ, Hurley LH. Direct evidence for a G-quadruplex in a promoter region and its targeting with a small molecule to repress c-MYC transcription. PNAS. 2002, 99 (18): 11593–8 [2007-06-20]. PMC 129314 . PMID 12195017. doi:10.1073/pnas.182256799. （原始內容存檔於2007-10-01）.
• Rawal P, Kummarasetti VB, Ravindran J, Kumar N, Halder K, Sharma R, Mukerji M, Das SK, Chowdhury S. Genome-wide prediction of G4 DNA as regulatory motifs: Role in Escherichia coli global regulation. Genome Res. 2006, 16 (5): 644–55 [2007-06-20]. PMC 1457047 . PMID 16651665. doi:10.1101/gr.4508806. （原始內容存檔於2007-09-12）.
• Xu Hou, Wei Guo, Fan Xia, Fu-Qiang Nie, Hua Dong, Ye Tian, Liping Wen, Lin Wang, Liuxuan Cao, Yang Yang, Jianming Xue, Yanlin Song, Yugang Wang, Dongsheng Liu, and Lei Jiang. A biomimetic potassium responsive nanochannel: G-quadruplex DNA conformational switching in a synthetic nanopore. J. Am. Chem. Soc. 2009, 131 (22): 7800–7805 [2015-06-19]. PMID 19435350. doi:10.1021/ja901574c. （原始內容存檔於2022-03-15）.
• Neidle & Balasubramanian (編). Quadruplex Nucleic Acids. 2006 [2007-06-20]. ISBN 0-85404-374-8. （原始內容存檔於2007-09-30）.

外部連結

• Nanopore and Aptamer Biosensor group（頁面存檔備份，存於互聯網檔案館）{NAB group}

四聯體網站

• COST MP0802 Quadruplex Network – the European network of G-quadruplex community: From first principles to applications
• Quadruplex.org – a website to serve the quadruplex community
• G-Quadruplex World（頁面存檔備份，存於互聯網檔案館） – a website to discuss publications and other information of interest to those working in the field of G-quadruplexes
• Quadbase – downloadable data on predicted G-quadruplexes
• Greglist – a database listing potential G-quadruplex regulated genes
• Database on Quadruplex information: QuadBase from IGIB
• GRSDB（頁面存檔備份，存於互聯網檔案館）- a database of G-quadruplexes near RNA processing sites.
• GRS_UTRdb- a database of G-quadruplexes in the UTRs.
• G-quadruplex Resource Site（頁面存檔備份，存於互聯網檔案館）
• non-B Motif Search Tool at non-B DB- a web server to predict G-quadruplex forming motifs and other non-B DNA forming motifs from users' DNA sequences.

預測G-四聯體的工具

• Quadparser: Downloadable program for finding putative quadruplex-forming sequences（頁面存檔備份，存於互聯網檔案館） from Balasubramanian's group.
• QGRS Mapper: a web-based application for predicting G-quadruplexes in nucleotide sequences and NCBI genes（頁面存檔備份，存於互聯網檔案館） from Bagga's group.
• Quadfinder: Tool for Prediction and Analysis of G Quadruplex Motifs in DNA/RNA Sequences from Maiti's group, IGIB, Delhi, India^{[永久失效連結]}