Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The regulation of p53 activity through the MDM2 negative feedback loop is driven in part by an extrinsic ATM-pulse that maintains p53 oscillations in response to DNA damage. We report here that the p53 pathway has evolved an intrinsic positive feedback loop that is maintained by the p53-inducible gene product p21(WAF1). p21-null cancer cells have defects in p53 protein turnover, reductions in MDM2-mediated degradation of p53, and reduced DNA damage-induced ubiquitination of p53. TLR3-IRF1 or ATM-dependent signaling to p53 is defective in p21-null cells and complementation of the p21 gene in p21-null cancer cells restores the p53 transcriptional response. The mechanism of p53 inactivity in p21-null cells is linked to a p53 protein equilibrium shift from chromatin into cytosolic fractions and complementation of the p21 gene into p21-null cells restores the nuclear localization of p53. A loss of p53 transcriptional function in murine B-cells heterozygous or homozygous null for p21 highlights a p21-gene dosage effect that maintains the full p53 transcriptional response. ATM inhibition results in nuclear exclusion of p53 highlighting a positive genetic interaction between ATM and p21. P21 protein oscillates in undamaged proliferating cells, and reductions of p21 protein using siRNA eliminate the DNA damage-induced p53 pulse. The p53 transcription program has evolved a negative feedback loop maintained by MDM2 that is counteracted by a positive feedback loop maintained by ATM-p21 the balance of which controls the specific activity of p53 as a transcription factor.
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PMID:p21(WAF1) is component of a positive feedback loop that maintains the p53 transcriptional program. 2136 73

Objective of this study was to investigate the mechanism of the biological function damage resulting from increased ROS in peripheral blood stem cells during peripheral blood stem cell transplantation. Bone marrow hematopoietic stem cells (BMHSC) were cultured at the oxygen concentration imitated according to the bone marrow oxygen concentration (5% O2) including mean venous oxygen concentration (12% O2), mean arterial oxygen concentration (20% O2). The ROS level in BMHSC was detected by using fluorescent probe, the percentage of BM-HSC in cell cycle was determined by flow cytometry, the apoptosis rate was assayed by Annexin V/PI double staining, the expression levels of ATM gene and P21 protein were measured by PCR and Western respectively. The results showed that as compared with control group (5% O2), the ROS levels were lower, the percentage of cells in G1, S,G2/M phase increased (P < 0.01), the apoptosis rate of cells obviously increased (P < 0.01), the expression level of ATM gene obviously decreased (P < 0.01), while the expression level of P21 protein significantly was enhanced (P < 0.01) in 12% O2, 20% O2 and 5%-12%-20% O2 groups. It is concluded that ROS results in the apoptosis of BMHSC through inhibiting the expression of ATM gene and activating P21 protein.
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PMID:[Influence of reactive oxygen species on mouse bone marrow hematopoietic stem cell apoptosis]. 2415 42