p53
p53 is a tumor-suppressor protein, made from the TP53 gene. It acts as a master switch (a transcription factor) in your cell's response to stress, such as DNA damage, low oxygen, rogue oncogene activity, or starvation. Once switched on, it turns on gene programs that can halt the cell cycle, repair DNA, trigger cell death (apoptosis), or push the cell into senescence. Which path it takes depends on how strong the stress is, the cell type, and the surrounding signals. Because p53 can both kill and retire damaged cells, it plays a double role in aging. It suppresses tumors, yet when it stays active too long, it can drain your stem-cell pools and pile up senescent cells. Germline TP53 variants and acquired TP53 mutations are the most common changes in human cancers, and altered p53 activity shows up in many age-related diseases beyond cancer.
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