Abstract

Cancer is a leading cause of death. It kills an estimated 10 million people yearly, and affects ten times as many. It can develop from gene mutations causing unrestrained cell division, and radiation therapy is a common method of treatment. In particular, phosphatase and tensin homolog (PTEN) is a gene commonly mutated in cancer, and the PTEN protein is involved in maintaining chromatin condensation. HP1α is a protein that helps maintain heterochromatin stability. Utilizing both, we aimed to answer the question, "what is the impact of chromatin condensation on Rad51--mediated DNA damage repair?" Wild type TS/A, isogenic PTEN-knockout (KO) C6, HP1α-transfected C6, and HP1α mutant V22M-transfected C6 cells were compared for levels of DNA damage and repair protein Rad51 levels after exposure to 10Gy radiation. We show that when PTEN is deleted from the genome, cells become unable to recruit Rad51 in the presence of DNA double strand breaks (DSBs). When HP1α is transfected into PTEN-KO cells, the cell’s ability to repair DNA is largely restored. However, when the HP1α mutant V22M is transfected, the cell becomes unable to repair DNA damage, even more so than untransfected PTEN-KO cells. Our results indicate that PTEN plays a crucial role in Rad51--mediated DNA repair when DNA DSBs are detected, and that the introduction of HP1α in a PTEN-KO cell improved its ability to recruit repair proteins other than Rad51. This is important, as further understanding of DNA repair mechanisms could help us develop better methods of cancer treatment in the future.