GENOMIC INSTABILITY

基因组不稳定

• 批准号: 6288737
• 负责人: VILHELM A. BOHR
• 金额: --
• 依托单位: NATIONAL INSTITUTE ON AGING
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6288737
• 关键词: DNA damage; DNA repair; DNA replication; aging; gene expression; gene interaction; genome; guanine nucleotide binding protein; human tissue; neoplasm /cancer genetics; oncoprotein p21; telomere; tissue /cell culture; tumor suppressor genes

Summary of workThe protein p21 (Cip1, Waf1, Sdi1) is a potent inhibitor of cyclin dependent kinases (CDKs) and cyclins. P21 can also block DNA replication through its interaction with the proliferating cell nuclear antigen (PCNA) which is an auxiliary factor for polymerase delta;. In addition to its role on replication, PCNA is clearly implicated in the repair resynthesis step of nucleotide excision repair (NER). Since PCNA particpates in both DNA repair and replication, it has been speculated that p21 might also regulate NER through its interaction with PCNA. Previous studies on the role of p21 on NER have yielded contradictory results that make it difficult to reach a general consensus with regard to the precise role of p21 in NER. In this study, we have investigated the effect of p21 on NER both in vitro and in vivo using purified fragments of p21 containing either the CDK-binding domain or the PCNA- binding domain of the protein. In the in vitro studies DNA repair synthesis was measured in extracts from normal human fibroblasts using plasmids damaged by ultraviolet (UV) irradiation. A permeabilized cell system and electroporation of intact cells were utilized for in vivo studies. The results show that the C-terminal domain of the p21 protein, which binds to PCNA, inhibits NER both in vitro and in vivo. A 50% percent inhibition of in vitro NER occurred at a ratio of 50:1 p21 C-terminus to PCNA monomer. This is a specific function of the C- terminal end of p21 since the N-terminal of the protein had no effect on nucleotide excision repair. Our results suggest that the inhibition occurs at the resynthesis step of the repair process. We further demonstrate that the inhibition of DNA repair is mediated via binding of p21 to PCNA since it is relieved by addition of purified PCNA protein. We conclude that the effect of p21 on DNA repair occurs at much higher concentrations than its effect on DNA replication. P21 might serve as an intracellular regulator of these two processes - Genomic instability, DNA repair, p21, proliferating cell nuclear antigen

p21蛋白（Cip 1，Waf 1，Sdi 1）是细胞周期蛋白依赖性激酶（CDKs）和细胞周期蛋白的有效抑制剂。P21还可以通过与增殖细胞核抗原（PCNA）的相互作用来阻断DNA复制，增殖细胞核抗原是聚合酶δ的辅助因子。除了其在复制中的作用外，PCNA还明显涉及核苷酸切除修复（NER）的修复再合成步骤。由于PCNA参与DNA的修复和复制，推测p21也可能通过与PCNA的相互作用调节NER。以往关于p21在NER中作用的研究产生了相互矛盾的结果，这使得人们很难就p21在NER中的确切作用达成普遍共识。在这项研究中，我们已经调查了NER的p21在体外和体内使用纯化的片段p21含有的蛋白质的CDK结合结构域或PCNA结合结构域的影响。在体外研究中，使用紫外线（UV）照射损伤的质粒在正常人成纤维细胞提取物中测定DNA修复合成。透化细胞系统和完整细胞的电穿孔用于体内研究。结果表明，与PCNA结合的p21蛋白的C-末端结构域在体外和体内均抑制NER。当p21 C-末端与PCNA单体的比例为50：1时，对体外NER的抑制率为50%。这是p21的C-末端的特异性功能，因为蛋白质的N-末端对核苷酸切除修复没有影响。我们的研究结果表明，抑制发生在修复过程中的再合成步骤。我们进一步证明了DNA修复的抑制是通过p21与PCNA的结合介导的，因为它通过加入纯化的PCNA蛋白而减轻。我们得出结论，p21对DNA修复的影响发生在比其对DNA复制的影响高得多的浓度。P21可能作为这两个过程的细胞内调节剂-基因组不稳定性，DNA修复，p21，增殖细胞核抗原