Fig. 2

The main signaling pathways of the p53 protein in the cell. DNA damage caused by various stress factors (UV radiation, radiation, viral infection) activates protein kinases ATR, ATM, DNA-PK, which belong to the PIKK family. One of the signaling pathways of these protein kinases includes the p53 protein, the degradation of which as a result slows down and its concentration increases. The p53 protein acts as a transcription factor, activating some genes (GADD45, MDM2, BAX, BAK, p21) and suppressing others (BCL-2, BCL-XL). In some signaling pathways, p53 interacts with other proteins, for example with mitochondrial anti-apoptotic proteins during the initiation of apoptosis [6]. One of the protein regulators of p53 is MDM2, which interacts with p53 according to the principle of negative feedback. The p53 protein enhances MDM2 transcription, while MDM2 acts as a ubiquitin ligase to promote p53 degradation. The p21 protein inhibits the complex of cyclin and cyclin-dependent kinases, in the event of DNA damage, preventing the transition from G1 to S phase and thus stopping the cell cycle. In the absence of the p21 protein, the cyclin-dependent kinase CDK phosphorylates the Rb protein, and the transcription factor E2F is involved in DNA synthesis. If DNA damage cannot be repaired, p53 initiates apoptosis, including regulating the expression of bcl-2 family genes