DNA聚合酶δ在DNA复制、DNA损伤识别与修复中发挥重要作用，本课题组前期研究发现，DNA聚合酶δ催化亚基POLD1随增龄表达下调，最终导致衰老进程加快。然而POLD1的调控机制尚不十分明确，尤其是其转录调控机制。同时，我们发现RUNX1、Pax5和POLD1启动子区域均有结合，且RUNX1与Pax5具有相互作用。据此我们提出假说，衰老过程中RUNX1和Pax5形成转录复合物共同对POLD1进行转录调控。本研究拟以复制性衰老细胞模型和不同年龄健康人外周血淋巴细胞为研究对象，通过分析RUNX1、Pax5与POLD1的调控关系，最终揭示POLD1的转录调控机制，从而阐明细胞衰老的分子机制。同时，初步分析健康人群、骨质疏松患者、阿尔兹海默病患者外周血淋巴细胞中RUNX1、Pax5和POLD1的表达水平，RUNX1与Pax5相互作用情况等，为分析上述指标作为老年相关疾病标志物的可行性奠定基础。

DNA polymerase δ (DNA pol δ) plays a very important role in DNA replication and DNA damage repair. Our previous study showed that the expression level of POLD1 (the catalytic subunit of DNA pol δ) decreased during cellular senescence. However, the mechanism of POLD1 down-regulation in aging processes, especially the transcriptional regulatory mechanism of POLD1 is not clear. Our previous study finds that Pax5 and RUNX1 bind to the promoter of POLD1, and that Pax5 can interact with RUNX1, indicating POLD1 is regulated by Pax5/RUNX1 complex. In this study, human fetal lung fibroblast and lymphocyte will be used. The transcriptinal regulatory mechanism of POLD1 and cellular senescence mechanism will be finally uncovered by analysis of the regulatory relationship between RUNX1/Pax5 and POLD1. Moreover, the expression level of RUNX1/Pax5 and POLD1, interaction between RUNX1 and Pax5 will also be measured in the lymphocyte of healthy people, Alzheimer’s disease patients and osteoporosis patients to indicate the potential of the biomarkers of the diseases.