端粒DNA与非编码端粒RNA TERRA在体外形成分子间G-四链体复合物的研究

Research on the formation of intermolecular G-quadruplex complexes by telomeric DNA and non-coding telomeric RNA TERRA in vitro

端粒DNA和非编码端粒RNA TERRA(Telomeric Repeat-containing RNA)均由富含连续鸟嘌呤的串联重复序列组成,都可以形成G-四链体结构并阻止端粒酶对端粒的延伸,从而抑制癌细胞增殖能力。端粒DNA和TERRA还可以通过形成分子间G-四链体复合物来发挥作用,但此类研究较少。通过核磁共振(NMR)证明人源和蓝氏贾第鞭毛虫的端粒序列均可形成DNA-RNA分子间G-四链体复合物;通过圆二色谱(CD)和NMR滴定实验发现TERRA短链能与序列相当的端粒DNA短链进行竞争替换,使得已经形成的平行-反平行混杂型DNA-DNA G-四链体复合物转化为具有全平行构象的DNA-RNA G-四链体复合物,且DNA-RNA G-四链体复合物比DNA-DNA G-四链体复合物更加稳定。研究端粒DNA-RNA G-四链体复合物的结构和性质,可以为TERRA与端粒DNA的结合方式以及TERRA维持端粒稳定性的方式提供新的见解。

Telomeric DNA and TERRA(Telomeric repeat-containing RNA,a non-coding telomeric RNA)are consisted of tandem repeats rich in successive guanines,both can form G-quadruplex structures to inhibit the telomere extension by the telomerase and prevent the infinite proliferation of cancer cells.An intermolecular G-quadruplex complex can be formed between telomeric DNA and TERRA and has some functions,but little has been reported about this.Nuclear magnetic resonance(NMR)experiment showed that both human and Giardia lamblia telomeres formed DNA-RNA intermolecular G-quadruplex complexes.Based on the circular dichroism(CD)spectrum and NMR titration,it was found that,due to sharing the same sequence,a short sequence of TERRA was able to compete with and eventually replace the corresponding short telomeric DNA sequence within a DNA-DNA parallel-antiparallel hybrid intermolecular G-quadruplex complex.The resulting DNA-RNA G-quadruplex complex is induced into a full parallel conformation.In addition,the DNA-RNA G-quadruplex complex is more stable than the DNA-DNA G-quadruplex complex.Study on the structure and properties of telomeric DNA-RNA G-quadruplex complex can provide new insights into the interacting mode between TERRA and telomeric DNA and the way to maintain telomeric stability by TERRA.