RESUMO
Mutation of the tumor suppressor gene p53 is the most common genetic alteration observed in human tumors. However, the relationship between the mutation point of p53 and the transcriptional specificity is not so obvious. We prepared Saos-2 cells with various mutations of p53 that are found in human tumors, and examined the resulting transcriptional alterations in the cells. Loss of function and gain of function were observed in all p53 mutants. Hot-spot mutations of p53 are frequently found in tumor cells. We compared hot-spot mutations and other mutations of p53 and found that a more than 2-fold transcription of CADPS2, PIWIL4 and TRIM9 was induced by hot spot mutations, but not by other mutations. As PIWIL4 suppresses the p16(INK4A) and ARF pathway, restraining cell growth and genomic instability, induction of PIWIL4 expression may be one reason why hot-spot mutations are frequently found in tumor cells.
Assuntos
Genes p53 , Mutação , Transcrição Gênica , Proteínas Argonautas/fisiologia , Linhagem Celular Tumoral , Inibidor p16 de Quinase Dependente de Ciclina , Humanos , Proteínas de Neoplasias/fisiologia , Proteínas do Tecido Nervoso/genética , Proteínas de Ligação a RNA , Proteínas com Motivo Tripartido , Ubiquitina-Proteína Ligases/genéticaRESUMO
Phosphorylation is an important modification involved in the control of p53 activity. We examined the relationship between p53 phosphorylation and cell radiosensitivity. We prepared H1299 cells (p53-null) with various mutations of p53 at three sites (serine 15, 20 and 46) and examined the radiosensitivity of the cells. In three mutant forms of p53--S15A, S20A and S46A--serine was converted to alanine at these sites to prevent phosphorylation, and in two other mutant forms, S15D and S20D, serine was converted to aspartic acid to mimic phosphorylation. H1299 cells were more radioresistant than cells with wild-type p53. Cells with the S15A and S46A mutant forms of p53 were radiosensitive, whereas those with the S15D, S20A and S20D forms showed medium radiosensitivity. Thus the sensitivity of cells to ionizing radiation varies according to the site of phosphorylation of p53.
Assuntos
Proteína Supressora de Tumor p53/metabolismo , Carcinoma Pulmonar de Células não Pequenas/genética , Carcinoma Pulmonar de Células não Pequenas/metabolismo , Carcinoma Pulmonar de Células não Pequenas/radioterapia , Linhagem Celular Tumoral , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/radioterapia , Mutagênese Sítio-Dirigida , Fosforilação , Tolerância a Radiação , Proteína Supressora de Tumor p53/genéticaRESUMO
Mutation of p53 is the most common genetic alteration observed in human tumours and is reported to lead to variations in cell radiosensitivity. However, the relationship between the mutation point and the degree of radiosensitivity is unclear. Saos-2 cells with different mutations of p53 were prepared and examined for radiosensitivity. Cells with p53 mutations at codons 175, 244, 245, 273 and 282 were radioresistant, whereas those with mutations at codons 123, 195, 238 and 242 were radiosensitive. Mutations at codons 130, 143, 157, 168, 277, 280 and 286 resulted in medium radiosensitivity. Thus the sensitivity of Saos-2 cells to ionizing radiation varies with the mutation point of the p53 gene.
