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When p53 becomes stabilized and activated in hESCs, it increases p21 to establish a longer G1. This typically leads to abolition of S-phase entry, which stops the cell cycle in G1, leading to differentiation. Work in mouse embryonic stem cells has recently shown however that the expression of P53 does not necessarily lead to differentiation.
Part of this pathway includes alpha-interferon and beta-interferon, which induce transcription of the p53 gene, resulting in the increase of p53 protein level and enhancement of cancer cell-apoptosis. [88] p53 prevents the cell from replicating by stopping the cell cycle at G1, or interphase, to give the cell time to repair; however, it will ...
P53 function can also be responsible for a limited life span where mutations of the p53 gene causes expression of dominant-negative forms producing long lived animals. For example in an experiment using C. elegans , the increased life span of p53 mutants was found to depend on increased autophagy. [ 19 ]
Many cancers exhibit mutations in the p53 gene, but this mutation can only be detected through extensive DNA sequencing. Studies have shown that cells with p53 mutations have significantly lower levels of PUMA, making it a good candidate for a protein marker of p53 mutations, providing a simpler method for testing for p53 mutations. [44]
P53, p63, and p73 have similar features in their gene structures and functions but have also diverged evolutionarily. The p53 family evolved from an ancestor gene in unicellular life. [ 4 ] The ancestor gene functioned in germ line DNA protection early invertebrates. [ 5 ]
[9] p53 is also phosphorylated by the effector kinase CHK2. These phosphorylation events lead to stabilization and activation of p53 and subsequent transcription of numerous p53 target genes including CDK inhibitor p21 which lead to long-term cell-cycle arrest or even apoptosis. [15] ATM-mediated two-step response to DNA double strand breaks.
It cooperates with p53 to induce the activation of p53 target genes, thus activating cell-cycle checkpoints. [ 12 ] p53 itself is an important tumor-suppressor gene sometimes known by the epithet “the guardian of the genome.” hnRNP K’s close association with p53 demonstrates its importance in DNA damage control.
The p53 protein is a transcription factor that, when activated as part of the cell's response to stress, regulates many downstream target genes, including BID. However, p53 also has a transcription-independent role in apoptosis. In particular, p53 interacts with Bax, promoting Bax activation and the insertion of Bax into the mitochondrial membrane.