p53 gene is a human tumor suppressor gene. The gene encodes a protein with a molecular weight of 43.7 kDa, but the protein band appears at 53 KDa, shown by Marker, and is named p53. Because the protein contains a lot of proline, the electrophoresis speed is slowed down. Inactivation of the p53 gene plays an important role in tumor formation. Mdm2 Mutation does not coexist with p53 mutation, p53 is an important anti-cancer gene, its wild type causes apoptosis of cancer cells, thereby preventing canceration. p53 also has the function of helping cell gene repair defects.
Figure 1. Cartoon representation p53 DNA binding domain.
p53 is a tumor suppressor gene. In all malignant tumors, more than 50% of the mutations in this gene occur. The protein encoded by this gene is a transcriptional factor that controls the initiation of the cell cycle. Many signals about cell health are sent to the p53 protein. The protein is determined by whether or not to start cell division. If the cell is damaged and cannot be repaired, the p53 protein will be involved in the initiation process, causing the cell to die in apoptosis. Cells with p53 deficiency do not have this control and continue to divide even under adverse conditions. Like all other tumor suppressors, the p53 gene normally slows or monitors cell division. The gene "p53", which inhibits carcinogenesis in cells, determines the degree of DNA variation. If the variation is small, the gene promotes cell self-repair. If the DNA variation is large, "p53" induces apoptosis.
p53 is also an important tumor suppressor gene. Since the gene was first reported in 1979, more than 20,000 articles have been found on Medline. The p53 gene was originally thought to be an oncogene, but with the deepening of research in the past decade, the function of p53 as a tumor suppressor gene has gradually been revealed. Mutation of p53 gene has been found in more than 50% of human tumor tissues, which is the most common genetic alteration in tumors, indicating that the alteration of this gene is likely to be the main pathogenic factor in human tumors.
p53 gene is located on human chromosome 17 and contains 11 exons. The wild-type P53 protein encoded by the transcriptional translation consists of 393 amino acid residues and contains multiple functional domains. The N-terminal transcriptional activation domain (AD) AD1, AD2 is located at amino acid position 1-50, and binds to the universal transcription factor TF11D to function as a transcriptional activation function. TF11D is a complex composed of TBP (TATAbinding protain) and TAF (TBP associated factor). P53 binds to TAF in TF11D and acts on the TATA box in the downstream gene promoter to achieve transcriptional activation. The p53 gene growth inhibitory domain is located at amino acid position 65-90, is rich in proline, contains 5 repeats of pxxp sequence, and interacts with SH3 domain-containing proteins to link P53 to the message-transport pathway. P53 gene also has a sequence-specific DNA-binding domain located between 100-300 amino acids; the nuclear localization signal NLS is located at amino acid residues 316-325; the tetrameric oligomerization domain is located at amino acid residues 334-356; The C-terminal non-specific DNA regulatory domain, while in the event of DNA damage, P53 may complement other proteins to the site of injury, providing DNA damage signals. The ability of p53 to bind to DNA does not specifically bind to DNA, participates in the allosteric regulation of core-binding to DNA, and in the event of DNA damage, p53 may complement other proteins to the site of injury, providing DNA damage signals.
Figure 2. A schematic of the known protein domains in p53.
p53 in DNA Damage Response
p53 tumor suppressor is one of the major apoptotic signaling pathways. The p53 protein is a nuclear transcription factor that regulates apoptosis associated with genotoxic or cellular stress, growth arrest, or expression of multiple genes involved in aging. p53 protein levels are stable in response to stress stimuli, including DNA damage, nucleolar stress, metabolic stress, and carcinogenic stress. P53 activates DNA repair proteins when DNA is continuously destroyed. It can prevent growth by keeping the cell cycle at the G1/S regulatory point of DNA damage recognition - if the cell stays here for a long enough time, the DNA repair protein will have time to repair the damage and keep the cell if the DNA damage is Proved to be irreparable, it can trigger apoptosis (ie, programmed cell death). This is critical for the senescence response of short telomere WAF1/CIP1 encoding p21 and several other downstream genes. P21 can also mediate growth-related growth arrest and more permanent growth arrest associated with cellular senescence. The p21 gene contains several p53 response elements that mediate direct binding of the p53 protein, resulting in transcriptional activation of the gene encoding the p21 protein. The p53 and RB1 pathways are linked by p14ARF, increasing the likelihood that pathways may be mutually regulated. The expression of p53 can be stimulated by ultraviolet light, which can also cause DNA damage. In this case, p53 can initiate an event that causes tanning.
Figure 3. p53 pathway.
1. Bates S.; et al. p14ARF links the tumour suppressors RB and p53. Nature.1998, 395 (6698): 124–125.