Journal: Nucleic Acids Research

Article Title: A cancer persistent DNA repair circuit driven by MDM2, MDM4 (MDMX), and mutant p53 for recruitment of MDC1 and 53BP1 on chromatin

doi: 10.1093/nar/gkaf627

Figure Lengend Snippet: Reduced MDM2 protein in T47D cells causes reduced chromatin phosphoproteins 53BP1 and MDC1. ( A ) Experimental design workflow of the SILAC analysis (created in BioRender. Harmon, K. (2025) https://BioRender.com/oyd7ala ). Chromatin isolated from a mixture of T47D vector control cells (MDM2-competent) cultured in natural amino acid medium, and T47Dshmdm2 cells (MDM2-depleted) cultured in heavy isotope amino acid medium, was subjected to proteolysis followed by phospho-peptide purification and enrichment. Scatter plot represents the H/L ratio versus abundance of peptides identified by mass spectrometry, with those corresponding to TP53BP1 (magenta), TP53 (blue), MCM2 (green), and MDC1(brown) highlighted. ( B ) Chromatin (5 μg) isolated from T47D vector control, T47Dshmdm2, and T47Dshmdmx cells was subjected to SDS–PAGE/western blot analysis for 53BP1, MDC1, MCM4, lamin A/C, and mtp53. ( C and D ) IF of total 53BP1 (i), phospho-53BP1 ser25 (ii), or phospho- 53BP1 ser1778 (iii) within T47D vector control nuclei [(i) 528, (ii) 549, and (iii) 501], T47Dshmdm2 nuclei [(i) 549,(ii) 520, and (iii) 501], and T47Dshmdmx nuclei [(i) 623, (ii) 376, and (iii) 501]. Confocal images for six fields for each were acquired and the number of 53BP1 foci per nucleus from each cell population indicated above was determined. Representative data ( n = 3) with mean, 95% CI, and Kruskal–Wallis statistical significance test prepared as described in the “Materials and methods” section. **** Indicates a p-value less than or equal to 0.0001, ** indicates a p-value less than or equal to 0.01, * indicates a p-value less than or equal to 0.05, and ns is nonsignificant.

Article Snippet: Antibodies used for western blotting (WB), immunofluorescence staining (IF), immunoprecipitation (IP), and proximity ligation assay (PLA) were purchased from the following (usage denoted in parenthesis): rabbit p53 Sigma cat# A300-247A (PLA), and Proteintech cat# 10442-1- AP (WB); mouse p53 DO1 Santa Cruz Biotechnology cat# sc-126 (PLA and WB); mouse p53 DO1-HRP Santa Cruz Biotechnology cat# sc-126 HRP (WB); rabbit MDMX Proteintech cat# 17914-1-AP (WB); [ ] rabbit MDM2 R&D Systems cat# AF1244 (WB); rabbit 53BP1 Cell Signaling Technology cat# 4937 (WB and IF); rabbit phospho-Serine 177853BP1 Cell Signaling Technology cat# 2675 (WB and IF); rabbit phospho-Serine 2553BP1 Sigma cat# PLA 0126 (WB, IF, and PLA); rabbit MDC1 Sigma cat# PLA0016 (WB, IF, and PLA); rabbit MCM4 Cell Signaling Technology cat# 12973 (WB); mouse Actin-HRP Sigma cat# A3854 (WB); [ ] mouse Lamin A cat# SAB4200420 (WB); mouse PARP1 BD Biosciences cat# 51-6639GR (WB); goat 53BP1 Sigma cat# PLA0303 (PLA and IP); goat anti-mouse HRP Sigma cat# A3682 (WB); goat anti-rabbit Proteintech cat# SA00001-2 (WB); mouse Cyclin A Santa Cruz Biotechnology cat# sc-271682 (WB); rabbit Cyclin A Cell Signaling Technology cat# 67955S (IF); mouse Cyclin B Santa Cruz Biotechnology cat# sc-245 (WB); rabbit p21 Cell Signaling Technology cat# 2947S (WB); γH2AX phospho-Ser139 Cell Signaling Technology cat# 9718S (WB and IF); rabbit Poly ADP-Ribose Cell Signaling Technology cat# 83732S (WB); mouse MDM2 SMP14 Santa Cruz Biotechnology cat# sc-965 (IP); mouse IgG Santa Cruz Biotechnology cat# sc-2025 (IP); Purified mouse MDM2 4B2 [ ]; and purified mouse MDM2 2A9 [ ] were used for PLA and IP and prepared as described [ ].

Techniques: Multiplex sample analysis, Isolation, Plasmid Preparation, Control, Cell Culture, Purification, Mass Spectrometry, SDS Page, Western Blot

Journal: Nucleic Acids Research

Article Title: A cancer persistent DNA repair circuit driven by MDM2, MDM4 (MDMX), and mutant p53 for recruitment of MDC1 and 53BP1 on chromatin

doi: 10.1093/nar/gkaf627

Figure Lengend Snippet: 53BP1 in breast cancer cells interacts with both mtp53 and MDM2. ( A ) Relative abundance of mtp53, MDM2, MDMX, 53BP1, and MDC1 within whole cell extracts (20 μg) prepared from T47D (L194F) and MDA-MB-231 (R280K) cell lines determined by SDS–PAGE/western blot analysis. ( B–D ) Association of mtp53, MDM2, and 53BP1 in vivo measured using the PLA. PLA analyses of mtp53-53BP1 (panel B), MDM2-mtp53 (panel C), and MDM2-53BP1 (panel D) within T47D and MDA-MB-231 cells were performed as described in the “Materials and methods” section; primary antibodies are PLA rabbit anti-p53, PLA goat anti-53BP1, and mouse anti-MDM2 4B2. Confocal images for 4–6 fields for each were acquired and the number of PLA foci per nucleus for each cell population was determined ( n = 3 for T47D, n = 2 for MDA-MB-231). Representative data with mean, 95% CI, and Kruskal–Wallis statistical significance test prepared as described in the “Materials and methods” section from the indicated number of cells: Panel B vector (T47D = 276; MDA-MB-231 = 108), shmdmx (T47D = 239; MDA-MB-231 = 128), and shmdm2 (T47D = 310; MDA-MB-231 = 106); Panel C vector (T47D = 92; MDA-MB-231 = 104), shmdmx (T47D = 108; MDA-MB-231 = 131), and shmdm2 (T47D = 101; MDA-MB-231 = 136); Panel D vector (T47D = 761; MDA-MB-231 = 129), shmdmx (T47D = 529; MDA-MB-231 = 142), and shmdm2 (T47D = 964; MDA-MB-231 = 163). **** Indicates a p-value less than or equal to 0.0001, ** indicates a p-value less than or equal to 0.01, * indicates a p-value less than or equal to 0.05, and ns is nonsignificant.

Article Snippet: Antibodies used for western blotting (WB), immunofluorescence staining (IF), immunoprecipitation (IP), and proximity ligation assay (PLA) were purchased from the following (usage denoted in parenthesis): rabbit p53 Sigma cat# A300-247A (PLA), and Proteintech cat# 10442-1- AP (WB); mouse p53 DO1 Santa Cruz Biotechnology cat# sc-126 (PLA and WB); mouse p53 DO1-HRP Santa Cruz Biotechnology cat# sc-126 HRP (WB); rabbit MDMX Proteintech cat# 17914-1-AP (WB); [ ] rabbit MDM2 R&D Systems cat# AF1244 (WB); rabbit 53BP1 Cell Signaling Technology cat# 4937 (WB and IF); rabbit phospho-Serine 177853BP1 Cell Signaling Technology cat# 2675 (WB and IF); rabbit phospho-Serine 2553BP1 Sigma cat# PLA 0126 (WB, IF, and PLA); rabbit MDC1 Sigma cat# PLA0016 (WB, IF, and PLA); rabbit MCM4 Cell Signaling Technology cat# 12973 (WB); mouse Actin-HRP Sigma cat# A3854 (WB); [ ] mouse Lamin A cat# SAB4200420 (WB); mouse PARP1 BD Biosciences cat# 51-6639GR (WB); goat 53BP1 Sigma cat# PLA0303 (PLA and IP); goat anti-mouse HRP Sigma cat# A3682 (WB); goat anti-rabbit Proteintech cat# SA00001-2 (WB); mouse Cyclin A Santa Cruz Biotechnology cat# sc-271682 (WB); rabbit Cyclin A Cell Signaling Technology cat# 67955S (IF); mouse Cyclin B Santa Cruz Biotechnology cat# sc-245 (WB); rabbit p21 Cell Signaling Technology cat# 2947S (WB); γH2AX phospho-Ser139 Cell Signaling Technology cat# 9718S (WB and IF); rabbit Poly ADP-Ribose Cell Signaling Technology cat# 83732S (WB); mouse MDM2 SMP14 Santa Cruz Biotechnology cat# sc-965 (IP); mouse IgG Santa Cruz Biotechnology cat# sc-2025 (IP); Purified mouse MDM2 4B2 [ ]; and purified mouse MDM2 2A9 [ ] were used for PLA and IP and prepared as described [ ].

Techniques: SDS Page, Western Blot, In Vivo, Plasmid Preparation

Journal: Nucleic Acids Research

Article Title: A cancer persistent DNA repair circuit driven by MDM2, MDM4 (MDMX), and mutant p53 for recruitment of MDC1 and 53BP1 on chromatin

doi: 10.1093/nar/gkaf627

Figure Lengend Snippet: The MDM2–53BP1 interaction is promoted by the mtp53 C-terminus. ( A ) The C-terminus of mtp53 R273H within MDA-MB-468 was modified using CRISPR–Cas9 to create the cell line MDA-MB-468 R273Hfs347Δ360-393 (termed G6; mtp53 derivative R273HΔC). ( B ) Relative protein levels of 53BP1, MDM2, and mtp53 within MDA-MB-468 (25, 12.5, 6.25, and 3.125 μg) and G6 (25 μg) cell lines was examined by SDS–PAGE/western blot analysis. ( C ) Loss of mtp53 C-terminus disrupts mtp53 co-IP with MDM2. Extracts from MDA-MB-468 and G6 cell lines were incubated with either normal mouse IgG (negative control) or anti-MDM2 antibodies 4B2 (lanes 1–7) or SMP14 (lanes 8–14), and IP reactions were examined for MDM2 and mtp53 by western blot analysis. Lanes 1–7: 4B2 IP reactions from 800 μg of extract (input); lanes contain 10% of total IP and 2% of input. Lanes 8–14: SMP14 IP reactions from 1600 μg of extract; lanes contain 12.5% each IP and 0.5% of input. Lanes labeled 2× (lane 7 for the 4B2 IPs and lane 14 for the SMP14 IPs) contain twice the amount of the G6 extract MDM2 IP; a lighter exposure of mtp53 input is presented due to the vast excess of mtp53 compared to MDM2 within the MDA-MB-468 cell lines. ( D–F ) PLA analysis of mtp53–53BP1 (panel D), MDM2–mtp53 (panel E), and MDM2–53BP1 (panel F) in MDA-MB-468 and G6. PLA analysis of the indicated proteins was measured using PLA rabbit anti-p53, PLA goat anti-53BP1, and mouse anti-MDM2 2A9 antibodies. Confocal images for 3–5 fields for each were acquired and the number of PLA foci per nucleus for each cell population was determined ( n = 2). Representative data with mean, 95% CI, and Kruskal–Wallis statistical significance test prepared as described in the “Materials and methods” section from the indicated number of cells in panel: (D) R273H = 120; R273HΔC = 144; (E) R273H = 131; R273HΔC = 159; (F) R273H = 102; R273HΔC = 138. **** Indicates a p-value less than or equal to 0.0001.

Article Snippet: Antibodies used for western blotting (WB), immunofluorescence staining (IF), immunoprecipitation (IP), and proximity ligation assay (PLA) were purchased from the following (usage denoted in parenthesis): rabbit p53 Sigma cat# A300-247A (PLA), and Proteintech cat# 10442-1- AP (WB); mouse p53 DO1 Santa Cruz Biotechnology cat# sc-126 (PLA and WB); mouse p53 DO1-HRP Santa Cruz Biotechnology cat# sc-126 HRP (WB); rabbit MDMX Proteintech cat# 17914-1-AP (WB); [ ] rabbit MDM2 R&D Systems cat# AF1244 (WB); rabbit 53BP1 Cell Signaling Technology cat# 4937 (WB and IF); rabbit phospho-Serine 177853BP1 Cell Signaling Technology cat# 2675 (WB and IF); rabbit phospho-Serine 2553BP1 Sigma cat# PLA 0126 (WB, IF, and PLA); rabbit MDC1 Sigma cat# PLA0016 (WB, IF, and PLA); rabbit MCM4 Cell Signaling Technology cat# 12973 (WB); mouse Actin-HRP Sigma cat# A3854 (WB); [ ] mouse Lamin A cat# SAB4200420 (WB); mouse PARP1 BD Biosciences cat# 51-6639GR (WB); goat 53BP1 Sigma cat# PLA0303 (PLA and IP); goat anti-mouse HRP Sigma cat# A3682 (WB); goat anti-rabbit Proteintech cat# SA00001-2 (WB); mouse Cyclin A Santa Cruz Biotechnology cat# sc-271682 (WB); rabbit Cyclin A Cell Signaling Technology cat# 67955S (IF); mouse Cyclin B Santa Cruz Biotechnology cat# sc-245 (WB); rabbit p21 Cell Signaling Technology cat# 2947S (WB); γH2AX phospho-Ser139 Cell Signaling Technology cat# 9718S (WB and IF); rabbit Poly ADP-Ribose Cell Signaling Technology cat# 83732S (WB); mouse MDM2 SMP14 Santa Cruz Biotechnology cat# sc-965 (IP); mouse IgG Santa Cruz Biotechnology cat# sc-2025 (IP); Purified mouse MDM2 4B2 [ ]; and purified mouse MDM2 2A9 [ ] were used for PLA and IP and prepared as described [ ].

Techniques: Modification, CRISPR, SDS Page, Western Blot, Co-Immunoprecipitation Assay, Incubation, Negative Control, Labeling

Journal: Nucleic Acids Research

Article Title: A cancer persistent DNA repair circuit driven by MDM2, MDM4 (MDMX), and mutant p53 for recruitment of MDC1 and 53BP1 on chromatin

doi: 10.1093/nar/gkaf627

Figure Lengend Snippet: The MDM2-mtp53 and MDM2–53BP1 interactions are Nutlin 3a sensitive. ( A ) Western blot analysis of whole cell extracts (10 μg) from MCF7 and T47D cell line populations treated for the indicated time with either vehicle or 10 μM Nutlin 3a (labeled N3a or “+” in graphs) for the indicated proteins. ( B ) Nutlin 3a does not inhibit T47D cell cycle progression. Twenty-four hour post-treatment with either vehicle or 10 μM Nutlin 3a, cells were labeled with EdU for 20 min and assayed for Cyclin A2 by immunofluorescence. Confocal images from at least three fields were acquired and the number of EdU + and Cyclin A + nuclei were quantified (tabulated in S4, panel C) in each population of vehicle-treated [vector = 289; shmdmx = 278; shmdm2 = 249] and Nutlin 3a-treated [vector = 227; shmdmx = 283; shmdm2 = 245] cells. The S/G2 fraction (total Cyclin A + nuclei) for vehicle-treated: vector = 33.6%, shmdmx = 37.8%, shmdm2 = 36.8%; Nutlin 3a-treated: vector = 38.3%, shmdmx = 27.0%, shmdm2 = 29.4%. ( C and D ) Nutlin 3a disrupts mtp53–MDM2 and 53BP1–MDM2 PLA foci in T47D. Twenty-four hour post-treatment with vehicle or 10 μM Nutlin 3a cell populations PLA interactions were measured between MDM2–mtp53 (panel C) and MDM2–53BP1 (panel D) using PLA rabbit anti-p53, PLA goat anti-53BP1, and mouse anti-MDM2 4B2 primary antibodies. Confocal images for 4–6 fields for each were acquired and the number of PLA foci per nucleus from each cell population was determined ( n = 2 for panel C and n = 3 for panel D). Representative data with mean, 95% CI, and Kruskal–Wallis statistical significance test prepared as described in the materials and methods from the indicated number of cells in panel: (C) vehicle-treated [vector = 328; shmdmx = 298; shmdm2 = 249], Nutlin 3a-treated [vector = 323; shmdmx = 364; shmdm2 = 285] and (D) vehicle-treated [vector = 543; shmdmx = 548; shmdm2 = 455], Nutlin 3a-treated [vector = 610; shmdmx = 545; shmdm2 = 618]. **** Indicates a p-value less than or equal to 0.0001.

Article Snippet: Antibodies used for western blotting (WB), immunofluorescence staining (IF), immunoprecipitation (IP), and proximity ligation assay (PLA) were purchased from the following (usage denoted in parenthesis): rabbit p53 Sigma cat# A300-247A (PLA), and Proteintech cat# 10442-1- AP (WB); mouse p53 DO1 Santa Cruz Biotechnology cat# sc-126 (PLA and WB); mouse p53 DO1-HRP Santa Cruz Biotechnology cat# sc-126 HRP (WB); rabbit MDMX Proteintech cat# 17914-1-AP (WB); [ ] rabbit MDM2 R&D Systems cat# AF1244 (WB); rabbit 53BP1 Cell Signaling Technology cat# 4937 (WB and IF); rabbit phospho-Serine 177853BP1 Cell Signaling Technology cat# 2675 (WB and IF); rabbit phospho-Serine 2553BP1 Sigma cat# PLA 0126 (WB, IF, and PLA); rabbit MDC1 Sigma cat# PLA0016 (WB, IF, and PLA); rabbit MCM4 Cell Signaling Technology cat# 12973 (WB); mouse Actin-HRP Sigma cat# A3854 (WB); [ ] mouse Lamin A cat# SAB4200420 (WB); mouse PARP1 BD Biosciences cat# 51-6639GR (WB); goat 53BP1 Sigma cat# PLA0303 (PLA and IP); goat anti-mouse HRP Sigma cat# A3682 (WB); goat anti-rabbit Proteintech cat# SA00001-2 (WB); mouse Cyclin A Santa Cruz Biotechnology cat# sc-271682 (WB); rabbit Cyclin A Cell Signaling Technology cat# 67955S (IF); mouse Cyclin B Santa Cruz Biotechnology cat# sc-245 (WB); rabbit p21 Cell Signaling Technology cat# 2947S (WB); γH2AX phospho-Ser139 Cell Signaling Technology cat# 9718S (WB and IF); rabbit Poly ADP-Ribose Cell Signaling Technology cat# 83732S (WB); mouse MDM2 SMP14 Santa Cruz Biotechnology cat# sc-965 (IP); mouse IgG Santa Cruz Biotechnology cat# sc-2025 (IP); Purified mouse MDM2 4B2 [ ]; and purified mouse MDM2 2A9 [ ] were used for PLA and IP and prepared as described [ ].

Techniques: Western Blot, Labeling, Immunofluorescence, Plasmid Preparation

Journal: Nucleic Acids Research

Article Title: A cancer persistent DNA repair circuit driven by MDM2, MDM4 (MDMX), and mutant p53 for recruitment of MDC1 and 53BP1 on chromatin

doi: 10.1093/nar/gkaf627

Figure Lengend Snippet: MDM2 promotes 53BP1–MDC1 complex formation. ( A ) Reduced 53BP1–MDC1 PLA foci in T47D lacking MDM2. EdU-labeled T47D vector and shmdm2 cells were assayed for 53BP1–MDC1 PLA foci using PLA goat anti-53BP1 and PLA rabbit anti-MDC1 antibodies. Shown under representative images ( n = 3) is the number of EdU + nuclei identified within each cell population and graphed is the number of PLA foci per nucleus. For the PLA analysis representative data with mean, 95% CI, and Kruskal–Wallis statistical significance test prepared as described in the “Materials and methods” section from the indicated number of cells: vector (total = 329, S-phase = 100, G1-G2 = 229); shmdm2 (total = 251, S-phase = 79, G1-G2 = 172). ( B ) Activation of the DDR in T47D cell lines by Etoposide but not Nutlin-3a. Whole cell extracts (20 μg) from T47D cell lines treated with either 50 μM Etoposide for 5 h (Etop), or 10 μM Nutlin 3a for 24 h (N3a) were analyzed for the indicated proteins by WB. ( C and D ) MDC1–53BP1 PLA foci are disrupted by both DDR activation and Nutlin 3a. MDC1–53BP1 PLA analyses were performed within each T47D cell line at the indicated time points post Etoposide treatment (panel C) or 24 h-post Nutlin 3a treatment (panel D) using PLA goat anti-53BP1 and PLA rabbit anti-MDC1. Confocal images for 3–6 fields for each were acquired and the number of PLA per nucleus from each cell population was determined ( n = 3 for panel C and n = 3 for panel D). Representative data with mean, 95% CI, and Kruskal–Wallis statistical significance test prepared as described in the “Materials and methods” section from the indicated number of cells in panel: (C) vehicle-treated (0 h Etop) [vector = 208; shmdmx = 198; shmdm2 = 247], 2 h Etoposide [vector = 205; shmdmx = 184; shmdm2 = 231], 5 h Etoposide [vector = 189; shmdmx = 224; shmdm2 = 176]; (D) vehicle-treated [vector = 198; shmdmx = 270; shmdm2 = 336] and Nutlin 3a-treated [vector = 380; shmdmx = 339; shmdm2 = 252]. **** Indicates a p-value less than or equal to 0.0001, ** indicates a p-value less than or equal to 0.01, * indicates a p-value less than or equal to 0.05, and ns is nonsignificant.

Article Snippet: Antibodies used for western blotting (WB), immunofluorescence staining (IF), immunoprecipitation (IP), and proximity ligation assay (PLA) were purchased from the following (usage denoted in parenthesis): rabbit p53 Sigma cat# A300-247A (PLA), and Proteintech cat# 10442-1- AP (WB); mouse p53 DO1 Santa Cruz Biotechnology cat# sc-126 (PLA and WB); mouse p53 DO1-HRP Santa Cruz Biotechnology cat# sc-126 HRP (WB); rabbit MDMX Proteintech cat# 17914-1-AP (WB); [ ] rabbit MDM2 R&D Systems cat# AF1244 (WB); rabbit 53BP1 Cell Signaling Technology cat# 4937 (WB and IF); rabbit phospho-Serine 177853BP1 Cell Signaling Technology cat# 2675 (WB and IF); rabbit phospho-Serine 2553BP1 Sigma cat# PLA 0126 (WB, IF, and PLA); rabbit MDC1 Sigma cat# PLA0016 (WB, IF, and PLA); rabbit MCM4 Cell Signaling Technology cat# 12973 (WB); mouse Actin-HRP Sigma cat# A3854 (WB); [ ] mouse Lamin A cat# SAB4200420 (WB); mouse PARP1 BD Biosciences cat# 51-6639GR (WB); goat 53BP1 Sigma cat# PLA0303 (PLA and IP); goat anti-mouse HRP Sigma cat# A3682 (WB); goat anti-rabbit Proteintech cat# SA00001-2 (WB); mouse Cyclin A Santa Cruz Biotechnology cat# sc-271682 (WB); rabbit Cyclin A Cell Signaling Technology cat# 67955S (IF); mouse Cyclin B Santa Cruz Biotechnology cat# sc-245 (WB); rabbit p21 Cell Signaling Technology cat# 2947S (WB); γH2AX phospho-Ser139 Cell Signaling Technology cat# 9718S (WB and IF); rabbit Poly ADP-Ribose Cell Signaling Technology cat# 83732S (WB); mouse MDM2 SMP14 Santa Cruz Biotechnology cat# sc-965 (IP); mouse IgG Santa Cruz Biotechnology cat# sc-2025 (IP); Purified mouse MDM2 4B2 [ ]; and purified mouse MDM2 2A9 [ ] were used for PLA and IP and prepared as described [ ].

Techniques: Labeling, Plasmid Preparation, Activation Assay

Journal: Nucleic Acids Research

Article Title: A cancer persistent DNA repair circuit driven by MDM2, MDM4 (MDMX), and mutant p53 for recruitment of MDC1 and 53BP1 on chromatin

doi: 10.1093/nar/gkaf627

Figure Lengend Snippet: Co-IP demonstrates a 53BP1–MDC1–MDM2 multiprotein complex. ( A ) Co-IP demonstrates a 53BP1–MDC1–MDM2 multiprotein complex. 53BP1 was immunoprecipitated from T47D CES as described in the “Materials and methods” section subjected to western blot analysis for 53BP1, MDC1, MDM2, and p53. Lanes are as follows: (1) cytoplasmic extract, (2) CES IP input, (3) IP with IgG, and (4) IP for 53BP1. ( B ) Inhibition of ATM promotes MDM2 activity. Western blot analysis for the indicated proteins within extracts (10 μg) from T47D populations treated for 24 h with either vehicle,10 μM ALRN-6924 (MDM2/X dual inhibitor), 10 μM KU-55933 (ATMi; ATM inhibitor) or both. ( C ) The MDM2 inhibitor ALRN-6924 reduces whereas the ATM inhibitor increases MDC1–53BP1 PLA foci in T47D. Twenty-four hour post treatment with either vehicle,10 μM ALRN-6924, 10 μM KU-55933 (ATMi) or both T47D vector and shmdm2 cells were labeled with EdU for 20 min and then assayed for 53BP1–MDC1 PLA foci using PLA goat anti-53BP1 and PLA rabbit anti-MDC1 antibodies. Confocal images for several fields were acquired and the number of PLA foci/nucleus from each cell population was determined. Representative data with mean, 95% CI, and Kruskal–Wallis statistical significance test prepared as described in the “Materials and methods” section from the indicated number of cells in: vehicle-treated [vector = 186; shmdm2 = 87], ATMi-treated [vector = 163; shmdm2 = 188], ALRN-6924-treated [vector = 196; shmdm2 = 176], ALRN-6924 + ATMi-treated [vector = 154; shmdm2 = 159]. **** Indicates a p-value less than or equal to 0.0001, ** indicates a p-value less than or equal to 0.01, * indicates a p-value less than or equal to 0.05, and ns is nonsignificant.

Article Snippet: Antibodies used for western blotting (WB), immunofluorescence staining (IF), immunoprecipitation (IP), and proximity ligation assay (PLA) were purchased from the following (usage denoted in parenthesis): rabbit p53 Sigma cat# A300-247A (PLA), and Proteintech cat# 10442-1- AP (WB); mouse p53 DO1 Santa Cruz Biotechnology cat# sc-126 (PLA and WB); mouse p53 DO1-HRP Santa Cruz Biotechnology cat# sc-126 HRP (WB); rabbit MDMX Proteintech cat# 17914-1-AP (WB); [ ] rabbit MDM2 R&D Systems cat# AF1244 (WB); rabbit 53BP1 Cell Signaling Technology cat# 4937 (WB and IF); rabbit phospho-Serine 177853BP1 Cell Signaling Technology cat# 2675 (WB and IF); rabbit phospho-Serine 2553BP1 Sigma cat# PLA 0126 (WB, IF, and PLA); rabbit MDC1 Sigma cat# PLA0016 (WB, IF, and PLA); rabbit MCM4 Cell Signaling Technology cat# 12973 (WB); mouse Actin-HRP Sigma cat# A3854 (WB); [ ] mouse Lamin A cat# SAB4200420 (WB); mouse PARP1 BD Biosciences cat# 51-6639GR (WB); goat 53BP1 Sigma cat# PLA0303 (PLA and IP); goat anti-mouse HRP Sigma cat# A3682 (WB); goat anti-rabbit Proteintech cat# SA00001-2 (WB); mouse Cyclin A Santa Cruz Biotechnology cat# sc-271682 (WB); rabbit Cyclin A Cell Signaling Technology cat# 67955S (IF); mouse Cyclin B Santa Cruz Biotechnology cat# sc-245 (WB); rabbit p21 Cell Signaling Technology cat# 2947S (WB); γH2AX phospho-Ser139 Cell Signaling Technology cat# 9718S (WB and IF); rabbit Poly ADP-Ribose Cell Signaling Technology cat# 83732S (WB); mouse MDM2 SMP14 Santa Cruz Biotechnology cat# sc-965 (IP); mouse IgG Santa Cruz Biotechnology cat# sc-2025 (IP); Purified mouse MDM2 4B2 [ ]; and purified mouse MDM2 2A9 [ ] were used for PLA and IP and prepared as described [ ].

Techniques: Co-Immunoprecipitation Assay, Immunoprecipitation, Western Blot, Inhibition, Activity Assay, Plasmid Preparation, Labeling

Journal: Nucleic Acids Research

Article Title: A cancer persistent DNA repair circuit driven by MDM2, MDM4 (MDMX), and mutant p53 for recruitment of MDC1 and 53BP1 on chromatin

doi: 10.1093/nar/gkaf627

Figure Lengend Snippet: Depletion of MDM2 increases poly(ADP-ribose) modification (PARylation) levels of chromatin bound proteins. Cytosolic ( A ) and chromatin ( B ) fractions were prepared from T47D cells with constitutive shmdm2, shmdmx, or mir30 shRNA-expressing vector cells treated with either vehicle (DMSO), or a combination of 1 mM temozolomide plus10 μM talazoparib (Temo + Tal) for 4 h, or combination of 1 mM temozolomide plus10 μM talazoparib (Temo + Tal) for 4 h and then replaced with fresh media for an additional 24 h. Ten micrograms of cytosolic or chromatin protein was loaded on a SDS–PAGE and protein levels were determined by western blot analysis using the indicated antibodies.

Article Snippet: Antibodies used for western blotting (WB), immunofluorescence staining (IF), immunoprecipitation (IP), and proximity ligation assay (PLA) were purchased from the following (usage denoted in parenthesis): rabbit p53 Sigma cat# A300-247A (PLA), and Proteintech cat# 10442-1- AP (WB); mouse p53 DO1 Santa Cruz Biotechnology cat# sc-126 (PLA and WB); mouse p53 DO1-HRP Santa Cruz Biotechnology cat# sc-126 HRP (WB); rabbit MDMX Proteintech cat# 17914-1-AP (WB); [ ] rabbit MDM2 R&D Systems cat# AF1244 (WB); rabbit 53BP1 Cell Signaling Technology cat# 4937 (WB and IF); rabbit phospho-Serine 177853BP1 Cell Signaling Technology cat# 2675 (WB and IF); rabbit phospho-Serine 2553BP1 Sigma cat# PLA 0126 (WB, IF, and PLA); rabbit MDC1 Sigma cat# PLA0016 (WB, IF, and PLA); rabbit MCM4 Cell Signaling Technology cat# 12973 (WB); mouse Actin-HRP Sigma cat# A3854 (WB); [ ] mouse Lamin A cat# SAB4200420 (WB); mouse PARP1 BD Biosciences cat# 51-6639GR (WB); goat 53BP1 Sigma cat# PLA0303 (PLA and IP); goat anti-mouse HRP Sigma cat# A3682 (WB); goat anti-rabbit Proteintech cat# SA00001-2 (WB); mouse Cyclin A Santa Cruz Biotechnology cat# sc-271682 (WB); rabbit Cyclin A Cell Signaling Technology cat# 67955S (IF); mouse Cyclin B Santa Cruz Biotechnology cat# sc-245 (WB); rabbit p21 Cell Signaling Technology cat# 2947S (WB); γH2AX phospho-Ser139 Cell Signaling Technology cat# 9718S (WB and IF); rabbit Poly ADP-Ribose Cell Signaling Technology cat# 83732S (WB); mouse MDM2 SMP14 Santa Cruz Biotechnology cat# sc-965 (IP); mouse IgG Santa Cruz Biotechnology cat# sc-2025 (IP); Purified mouse MDM2 4B2 [ ]; and purified mouse MDM2 2A9 [ ] were used for PLA and IP and prepared as described [ ].

Techniques: Modification, shRNA, Expressing, Plasmid Preparation, SDS Page, Western Blot

Journal: The Journal of Experimental Medicine

Article Title: Inherited IL-18BP deficiency in human fulminant viral hepatitis

doi: 10.1084/jem.20190669

Figure Lengend Snippet: Homozygous 40-nt deletion in IL18BP . (A) Pedigree of the family affected by FVH due to HAV. The patient is shown in black, whereas healthy individuals are shown in white. Where available, IL18BP mutation (NM_173042.2:c.508-19_528del) status is indicated in red. M, mutant. (B) Familial segregation of the mutation and its homozygous state in the patient were confirmed by Sanger sequencing. (C) Graph showing the predicted CADD scores and global AFs of the mutation found in the patient with FVH (red circle) and missense variants of IL18BP (blue circles) for which homozygotes were reported in GnomAD. The CADD-MSC score (90% confidence interval) for IL18BP is indicated by a dashed line. (D) The upper panel shows the exons (1–5) of the canonical IL18BP transcript; the bottom panel shows a diagram for IL-18BP. The signal peptide is highlighted in blue; the Ig domain is shown in red. Start and stop codons are indicated by an arrow and an asterisk, respectively. The c.508-19_528del is shown as a dashed box on the mRNA. The locations of IL18BP alleles from GnomAD are also shown on the protein diagram.

Article Snippet: Immunoblotting was performed with primary antibodies against the His-Tag (MA1-21315, 0.5 μg/ml; Thermo Fisher Scientific) and IL-18BP (AF119, 0.5 μg/ml; R&D Systems).

Techniques: Mutagenesis, Sequencing

Journal: The Journal of Experimental Medicine

Article Title: Inherited IL-18BP deficiency in human fulminant viral hepatitis

doi: 10.1084/jem.20190669

Figure Lengend Snippet: Impact of the IL18BP :c.508-19_528del on gene expression and function. (A) RT-qPCR showing IL18BP levels normalized against endogenous GAPDH expression in EBV-B cell lines from six healthy controls (black), the WT sibling (III.3, purple), and heterozygous family members: brother (III.2, red), father (II.4, blue), and mother (II.9, green). Relative IL18BP expression was determined by normalization against the mean value for WT cells, set to 1 (indicated by a dashed line). The values shown are the means of two independent experiments performed in duplicate. (B) Agarose gel electrophoresis showing aberrant splicing of the IL18BP mRNA in 3′ RACE on EBV-B cells from the heterozygous sibling (III.2), relative to a control cell line (C1) and the WT sibling (III.3). HPRT1 was used as the housekeeping gene control. (C) The nested PCR products from B were cloned, and colonies were sequenced. Diagram (left) and percentages (right) of WT (gray) and mutant (M1 in blue, M2 in red, and M3 in green) splice variants of the IL18BP transcript are shown. The start codon is located at position 1, and the stop codon is at 585, shown by an asterisk, on the WT transcript. The polyadenylation site is at position 1,252 and indicated by A n . (D) Expression levels of each splice variant (WT in gray, M1 in blue, M2 in red, and M3 in green) were determined and normalized against endogenous GAPDH expression levels by RT-qPCR on EBV-B cells from two healthy controls (C2 and C3) and family members. Graph shows the copy numbers of the mutant splice variants relative to the mean copy number for the WT allele in EBV-B cells from C2, C3, and III.3, which was set to 1 (indicated by a dashed line). The values are the means ± SEM of two independent experiments performed in duplicate. (E and F) Representative immunoblot images showing levels of the WT and mutant IL-18BP alleles, M1–M3 (E), and four missense alleles from GnomAD (F) in concentrated supernatants from transiently transfected COS7 cells. Immunoblotting was performed with the His tag antibody (top), and the membrane was then stripped and probed with the IL18BP antibody (bottom). (G) IL-18BP bioassay: IFN-γ production was measured in NK-92 cells stimulated with recombinant human IL-12 (100 pg/ml), IL-18 (10 ng/ml), and/or concentrated supernatants (100 µg/ml of total protein) of COS7 cells transiently transfected with either empty vector or the constructs expressing indicated IL-18BP variants. Graph is presented on a logarithmic scale with base of 10. The data are the means ± SEM of two independent experiments performed in duplicate using the supernatants shown in E and F and Fig. S1, F and G.

Article Snippet: Immunoblotting was performed with primary antibodies against the His-Tag (MA1-21315, 0.5 μg/ml; Thermo Fisher Scientific) and IL-18BP (AF119, 0.5 μg/ml; R&D Systems).

Techniques: Gene Expression, Quantitative RT-PCR, Expressing, Agarose Gel Electrophoresis, Control, Nested PCR, Clone Assay, Mutagenesis, Variant Assay, Western Blot, Transfection, Membrane, Bioassay, Recombinant, Plasmid Preparation, Construct

Journal: The Journal of Experimental Medicine

Article Title: Inherited IL-18BP deficiency in human fulminant viral hepatitis

doi: 10.1084/jem.20190669

Figure Lengend Snippet: Liver immunohistochemical profile of the patient. Liver tissue sections from a control individual, an unrelated patient with FVH due to HAV, and the deceased IL-18BP–deficient FVH patient reported in this study were subjected to immunohistochemical staining with the following markers: Hep Par-1, CD8, perforin, CD57, CD68, and IL-18. Representative zoom-in views of the original images at 400× magnification (Fig. S4) are shown. Hep Par-1 staining of IL-18BP–deficient patient’s liver tissue section displayed a background staining of macrophages, with lower intensity than hepatocytes. Some IL-18–positive hepatocytes and macrophages are indicated with blue and red arrows, respectively. Scale bar represents 50 µm.

Article Snippet: Immunoblotting was performed with primary antibodies against the His-Tag (MA1-21315, 0.5 μg/ml; Thermo Fisher Scientific) and IL-18BP (AF119, 0.5 μg/ml; R&D Systems).

Techniques: Immunohistochemical staining, Control, Staining

Journal: The Journal of Experimental Medicine

Article Title: Inherited IL-18BP deficiency in human fulminant viral hepatitis

doi: 10.1084/jem.20190669

Figure Lengend Snippet: IL-18/IL-18BP–mediated hepatotoxicity. (A and B) Coculture of mock- or HAV-infected hepatocytes (HepG2 and Huh7.5 cells) with NK-92 cells pretreated with IL-18, IL-18 + IL-18BP, or IL-18BP. HAV infection efficiencies in HepG2 and Huh7.5 cells were ∼40% and ~100%, respectively (Fig. S5 E; Materials and methods). The relative survival of calcein-AM–stained HepG2 or Huh7.5 cells was calculated based on the measurement of fluorescence retention within cells (A) and the amount of secreted albumin (B). Relative fluorescence and albumin levels were determined by normalization against the mean value for hepatocytes cocultured with NK92 cells without pretreatment (not treated [NT]), set to 100. A decrease in the fluorescence or in albumin levels indicates an increase in NK cell–induced hepatotoxicity. The data shown are the means ± SEM of three independent experiments performed in quadruplicate (n.s., not significant; **, P < 0.01; ***, P < 0.001; one-way ANOVA with Bonferroni correction for multiple comparisons). (C) A proposed model for IL-18BP deficiency underlying FVH. During the course of acute HAV infection in an otherwise healthy individual (left), IL-18 is secreted by macrophages in the liver. This cytokine activates lymphocytes, such as NK cells, inducing IFN-γ production and cytotoxicity to eliminate HAV-infected cells. IFN-γ also induces IL-18BP secretion by hepatocytes, macrophages, and other nonparenchymal cells (endothelial cells, fibroblasts, and hepatic stellate cells), to buffer IL-18 activity. However, in the absence of IL-18BP (right), excessive IL-18 activity leads to uncontrolled, massive immune-mediated hepatotoxicity and severe liver injury, as in the IL-18BP–deficient individual with FVH.

Article Snippet: Immunoblotting was performed with primary antibodies against the His-Tag (MA1-21315, 0.5 μg/ml; Thermo Fisher Scientific) and IL-18BP (AF119, 0.5 μg/ml; R&D Systems).

Techniques: Infection, Staining, Fluorescence, Activity Assay