Biswas Soumi, Samui Satyabrata, Das Apurba K, Pasadi Sanjeev, Muniyappa K, Naskar Jishu
Department of Biochemistry and Biophysics, University of Kalyani Nadia WB 741235 India
Department of Chemistry, Indian Institute of Technology Indore Indore 453552 India.
RSC Adv. 2020 Jul 14;10(44):26388-26396. doi: 10.1039/d0ra04780e. eCollection 2020 Jul 9.
Telomerase, a reverse transcriptase enzyme, is found to over express in most cancer cells. It elongates the telomere region by repeated adding of TTAGGG in the 3'-end and leads to excess cell proliferation which causes cancer. G-quadruplex (G4) formation can inhibit such telomere lengthening. So, stabilization of G4 structure as well as inhibition of telomerase activity is very promising approach in targeted cancer therapy. Herein, the aptitude of a synthetic dendritic peptide, C -(YEE)-E (peptide 1), to target specifically the human telomeric G4 DNA, dAGGG(TTAGGG), has been evaluated. Both biochemical and biophysical techniques including gel mobility shift assay, isothermal titration calorimetry and fluorescence spectroscopy have been employed for the purpose. Circular dichroism study reveals that the targeting results an increase in thermal stability of G4 DNA. Interestingly, replacement of N-terminal tyrosine residue of peptide 1 by valine, C -(VEE)-E, (peptide 2) consequences in loss of its G4 DNA targeting ability, although both the peptides exhibit comparable affinity toward double-stranded DNA. Of note, peptide 1 causes cessation of growth of human cancer cells (HeLa and U2OS) and induces apoptosis . But it has no significant inhibitory effect on the growth of normal human embryonic kidney 293 cells. Mechanistically, Telomeric Repeat Amplification Protocol (TRAP) assay indicates that peptide 1 effectively inhibits the telomerase activity in human cell extracts. Overall, this study demonstrates the usefulness of a synthetic dendritic peptide as an inhibitor of tumor cell growth by inducing apoptosis upon targeting the telomeric G4 DNA.
端粒酶是一种逆转录酶，在大多数癌细胞中过度表达。它通过在3'端重复添加TTAGGG来延长端粒区域，导致细胞过度增殖从而引发癌症。G-四链体（G4）的形成可以抑制这种端粒延长。因此，稳定G4结构以及抑制端粒酶活性是靶向癌症治疗中非常有前景的方法。在此，评估了一种合成树枝状肽C-(YEE)-E（肽1）特异性靶向人端粒G4 DNA，dAGGG(TTAGGG)的能力。为此采用了包括凝胶迁移率变动分析、等温滴定量热法和荧光光谱法在内的生化和生物物理技术。圆二色性研究表明，这种靶向作用导致G4 DNA的热稳定性增加。有趣的是，将肽1的N端酪氨酸残基替换为缬氨酸，即C-(VEE)-E（肽2），会导致其失去G4 DNA靶向能力，尽管这两种肽对双链DNA表现出相当的亲和力。值得注意的是，肽1会导致人癌细胞（HeLa和U2OS）生长停止并诱导凋亡。但它对正常人胚肾293细胞的生长没有显著抑制作用。从机制上讲，端粒重复序列扩增法（TRAP）分析表明，肽1能有效抑制人细胞提取物中的端粒酶活性。总体而言，这项研究证明了一种合成树枝状肽作为肿瘤细胞生长抑制剂的有效性，它通过靶向端粒G4 DNA诱导凋亡来实现这一作用。
