Fig 1: Role of p53 in DNA repair pathway. The DNA damage repair pathway involves activation of ATR for ssDNA breaks and ATM for dsDNA breaks. These kinases act on CHK1 and CHK2 to phosphorylate p53. Dephosphorylated p53 is ubiquitinated by MDM2 and rapidly degraded at the proteasome. Phosphorylation of p53 at S15 inhibits interaction with MDM2. p53 induces MDM2 transcription, ensuring that the lifetime of p53 is short. Phosphorylation and oligomerization state determine p53’s effect so that p53 acts as a switch to control the cell’s response to DNA damage. The tetramerized form most strongly binds DNA. Many other post-translational modifications of p53 have been described.
Fig 2: Changes in DNA damage repair-related proteins in brains of AD patients. (a) Protein carbonylation measured by ELISA. AD is 1.90 ± 0.26 × control. N = 20, p = 2.5 × 10−5. Protein carbonylation was confirmed using the 2,4-dinitrophenylhydrazine Western blot method (Fig. S01l,m). (b,c) Phospho- and total (pan-) ATM measured by ELISA. (b) Total ATM, AD = 0.655 ± 0.0017, Con = 0.752 ± 0.002, p = 0.0019. (c) Ratio of phospho-S1981-ATM/pan-ATM. AD = 0.996 ± 0.044, Con = 0.776 ± 0.058, p = 0.00045. (d–h) DNA repair markers measured by Western blot. (d) C/EBPβ normalized to control, AD = 79.53 ± 6.01, Control = 100 ± 6.40, N = 17, p = 0.027. (e) 14-3-3σ, AD = 85.6 ± 6.6, Con = 126.1 ± 16. N = 10, p = 0.034. (f) phospho-S15 p53 normalized to control, AD = 135.0 ± 12.0, Control = 100 ± 6.6. N = 15, p = 0.017. (g) γH2AX, a marker of DSBs, normalized to control, AD = 171.6 ± 10.3, Control = 100 ± 9.76. N = 20, p = 1.2 × 10–5. (h) Representative Western blot of γH2AX in AD and control samples. The combined γH2AX results are shown in the scatterplot (f). Western blots were run and developed in parallel under identical conditions. After imaging, blots were stripped and re-stained with histone H3 and actin. Images shown have been cropped for clarity of presentation. Original full-size blots and confirmatory Western blots of the ELISA results are presented in Supplementary Fig. S01a–s. Samples are temporal lobe, Brodmann’s area 38. Ages: AD = 77.2 ± 1.9 yr, Control = 76.3 ± 1.9 yr. PMI: AD = 14.33 ± 0.73 h, Control = 15.05 ± 0.98 h, N = 20, p = 0.56 (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\overline{\text{x}}}$$\end{document}x¯ ± SEM).
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