Bud32, also known as p53-related protein kinase (PRPK) is a member of the piD261 family of serine/threonine protein kinases. PRPK gene was first cloned from human interleukin-2-mediated cytotoxic T cells, and subsequently cloned in Xenopus, rat, chimpanzee, macaque, and leopard zebrafish have also confirmed the presence of this gene. RT-PCR analysis showed that testis, various cancer cell lines such as AsPC-1, PANC-1, and MIA PaCa-2 and activated mLT-positive cytotoxic T cells detected high PRPK expression, but low in heart, kidney, and spleen. expression. Saccharomyces cerevisiae piD261/Bud32 is another member of the piD261 family and has 64% similarity to human PRPK. The piD261 family belongs to eosinophil/threonine protein kinases, and piD261/Bud32 and PRPK are structurally different from typical serine/threonine protein kinases. The catalytic domain of a typical protein kinase consists of 300 to 350 amino acid residues, divided into 12 motifs, and specifically recognizes basic and prolyl amino acid residues.PiD261/Bud32 and PRPK are due to the motifs GXGXXG, AMK Mutations in RDLXXXN, APE, and deletion of the XI motif caused partial loss of function of the protease. In vitro experiments show that piD261/Bud32 can phosphorylate casein, but cannot recognize basic proteins such as histones. Overexpression of PRPK can partially complement the piD261/Bud32 gene deletion, resulting in reduced phenotypic changes in Saccharomyces cerevisiae cells and low stability. It can be seen that piD261/Bud32 and PRPK are functionally conservative.

p53 gene

p53 gene, human tumor suppressor gene. The gene encodes a protein with a molecular weight of 43.7KDa, but because the protein band appears at 53KDa shown by Marker, it is named P53. Because the protein contains a large amount of proline, the electrophoresis speed is slowed down. The inactivation of p53 gene plays an important role in tumor formation. The mdm2 mutation does not coexist with the P53 mutation. p53 is an important anti-cancer gene. Its wild type causes cancer cells to apoptosis, thereby preventing cancer gene. It also has the function of helping cells to repair defects in genes. Mutations of p53 increase cancer gene.

Figure 1. Protein structure of p53.

Introductions

p53 is a tumor suppressor gene. Mutations in this gene occur in more than 50% of all malignancies. 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. Whether or not to start cell division is determined by this protein. If the cell is damaged and cannot be repaired, the p53 protein will participate in the initiation process, causing the cell to die during apoptosis. P53-deficient cells 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" that inhibits canceration in cells will determine the degree of DNA mutation. If the mutation is small, this gene will promote cell self-repair. If the DNA mutation is large, "p53" will induce apoptosis.

Functions

DNA binding and transactivation of P53 protein also suggested its involvement in cell growth regulation. Flow cytometry was used to determine the expression of P53 in the cell cycle of individual cells, and it was found that activated lymphocytes had more P53 expression than non-activated cells And it increased with the cells from G1 to S phase to G2, M phase, suggesting that the correlation between P53 expression and cell growth is higher than entering the cell cycle or a specific time in the cycle. Transfection with a plasmid encoding antisense P53RNA non-transformation Cells cause the cell growth to stop completely. P53 antibody injection will enter the stationary cells of the growth cycle. It can inhibit the cells from entering the S phase, suggesting that P53 may be necessary for Go/G1-S conversion, but P53 antibodies have no effect on cells from dividing to S Sodium dibutyrate, which has an inhibitory effect on G1 cells, also inhibits P53 synthesis. These results suggest that the regulation of P53 on cell growth appears at least from G0-G1, or G1-S, but its mechanism of action has not yet been clarified. P53 protein can regulate cell growth by regulating Cipt gene expression, that is, P53 protein can stimulate Cipt gene to produce a protein with a molecular weight of 21KD. This protein can effectively inhibit certain enzyme activities that promote cells to enter mitosis through the cell cycle, thereby inhibiting cell growth. In addition, the inhibitory effect of P53 was accompanied by a decrease in the expression of cell growth nuclear antigen strains. Cell growth and nuclear antigens are involved in cellular DNA replication. Therefore, P53 may play a role by inhibiting cellular genes or gene products related to DNA replication.

Figure 2. Crystal structure of four p53 DNA binding domains (as found in the bioactive homo-tetramer) and has seven domains.

Reference:

1. Toufektchan, E; et al. The Guardian of the Genome Revisited: P53 Downregulates Genes Required for Telomere Maintenance, DNA Repair, and Centromere Structure. Cancers. 2018, 10 (5): 135.