Understanding the impact of DNA ADP-ribosylation on telomere function in cancer cells

研究总结/摘要 癌细胞必须采用端粒延长机制来确保复制永生。15%的癌症 细胞利用端粒替代性延长（ALT），一种同源重组介导的途径。 干扰ALT机制可以通过破坏参与ADP-核糖基化的酶来实现， 翻译后修饰，调节几个细胞过程，包括转录，代谢， DNA修复已证明对参与ADP-核糖基化的酶的药理学抑制是有效的。 在癌症治疗中具有巨大的生物医学价值。在过去的30年里，研究主要建立在密集的 研究ADP-核糖基化作为仅在蛋白质上发现的修饰。然而，新的证据表明， 出现核酸，DNA和RNA，是ADP的直接来源，甚至可能是主要来源， 核糖基化，尤其是在DNA损伤后。这种模式的转变对我们的 了解ALT中ADP-核糖基化的生理功能。因此，提高我们对 这种新的DNA修饰的细胞靶点和机制对于增强的 ADP-核糖靶向治疗，为ALT癌症患者实现更好的临床结果。 我发现端粒，染色体末端的特殊结构， ADP-核糖基化酶;聚ADP-核糖聚合酶（PARP 1），聚ADP-核糖糖水解酶（PARG）， 和一种新鉴定的因子，称为末端ADP-核糖水解酶（TARG 1）。我发现PARP 1 协调端粒DNA序列的ADP核糖基化，TARG 1与 PARG负责从端粒DNA中去除ADP-核糖。此外，我表明， TARG 1的表达引起ALT端粒的复制并发症， 对癌细胞生存能力的影响。在目标1中，我将进一步评估DNA ADP-核糖基化的影响， 调节端粒功能和ALT去除的因子缺陷。在目标2中，我将剖析 TARG 1和PARG（调节DNA ADP-核糖基化的因子）对癌细胞活力的共抑制，和 其中端粒功能障碍的贡献。本研究将为小说的研究提供新的、关键性的知识 和ADP核糖基化在ALT中的基本作用。通过探讨其放松管制对ALT的影响， 这项研究将为ADP核糖基化的失调如何有助于癌症治疗提供新的见解。

RESEARCH SUMMARY/ABSTRACT Cancer cells must employ a telomere lengthening mechanism to ensure replicative immortality. 15% of cancer cells utilize Alternative Lengthening of Telomeres (ALT), a homologous recombination-mediated pathway. Perturbation of the ALT mechanism can be achieved by disruption of enzymes involved in ADP-ribosylation, a post-translational modification that regulates several cellular processes including transcription, metabolism, and DNA repair. The pharmacological inhibition of enzymes involved in ADP-ribosylation has proven to be of immense biomedical value in cancer therapy. Over the last 30 years, studies have primarily built on intensive investigation of ADP-ribosylation as a modification that is exclusively found on proteins. Yet, new evidence is emerging that nucleic acids, DNA and RNA, are direct and perhaps even the predominant sources of ADP- ribosylation, especially in the aftermath of DNA damage. This paradigm shift has major implications for our understanding of the physiological function of ADP-ribosylation in ALT. Thus, improving our knowledge of the cellular targets and mechanisms of this new DNA modification will be vital for the development of enhanced ADP-ribose-targeting therapeutics that achieve better clinical outcomes for ALT cancer patients. I found that telomeres, specialized structures at the ends of the chromosomes, are targets of the major ADP-ribosylation enzymes; Poly ADP-ribose Polymerase (PARP1), Poly ADP-ribose Glycohydrolase (PARG), and a newly identified factor known as Terminal ADP-ribose Hydrolase (TARG1). I uncovered that PARP1 coordinates the ADP-ribosylation of telomeric DNA sequences and that TARG1, acting in conjunction with PARG, is responsible for the removal ADP-ribose from telomeric DNA. Furthermore, I show that the disruption of TARG1 expression provokes replicative complications at ALT telomeres that may have catastrophic consequences for cancer cell viability. In Aim 1, I will further assess the impact of DNA ADP-ribosylation and defects in factors that regulate its removal on telomere function and ALT. In Aim 2, I will dissect the impact of co-suppression of TARG1 and PARG, factors that regulate DNA ADP-ribosylation, on cancer cell viability, and the contribution of telomere dysfunction therein. This study will provide new and crucial knowledge on the novel and fundamental role of ADP-ribosylation in ALT. By exploring the impact that its deregulation has on ALT, this study will contribute new insights into how the deregulation of ADP-ribosylation contributes to cancer treatment.