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REACTIVITY SENSITIVITY MW (kDa) Isotype
H M R Mk Endogenous 15 Rabbit IgG

Western Blotting

Western blot analysis of extracts from various cell lines using Histone H2A.X (D17A3) XP® Rabbit mAb.

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Immunohistochemistry (Paraffin)

Immunohistochemical analysis of paraffin-embedded mouse colon using H2A.X (D17A3) Rabbit mAb.

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Immunohistochemistry (Paraffin)

Immunohistochemical analysis of paraffin-embedded human breast carcinoma using Histone H2A.X (D17A3) XP® Rabbit mAb.

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Immunohistochemistry (Paraffin)

Immunohistochemical analysis of paraffin-embedded human prostate carcinoma using Histone H2A.X (D17A3) XP® Rabbit mAb.

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Immunofluorescence (Immunocytochemistry)

Confocal immunofluorescent analysis of MCF7 cells using Histone H2A.X (D17A3) XP® Rabbit mAb (green). Actin filaments were labeled with DY-554 phalloidin (red).

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Western Blotting Protocol

For western blots, incubate membrane with diluted primary antibody in 5% w/v BSA, 1X TBS, 0.1% Tween® 20 at 4°C with gentle shaking, overnight.

NOTE: Please refer to primary antibody datasheet or product webpage for recommended antibody dilution.

A. Solutions and Reagents

NOTE: Prepare solutions with reverse osmosis deionized (RODI) or equivalent grade water.

  1. 20X Phosphate Buffered Saline (PBS): (#9808) To prepare 1 L 1X PBS: add 50 ml 20X PBS to 950 ml dH2O, mix.
  2. 10X Tris Buffered Saline (TBS): (#12498) To prepare 1 L 1X TBS: add 100 ml 10X to 900 ml dH2O, mix.
  3. 1X SDS Sample Buffer: Blue Loading Pack (#7722) or Red Loading Pack (#7723) Prepare fresh 3X reducing loading buffer by adding 1/10 volume 30X DTT to 1 volume of 3X SDS loading buffer. Dilute to 1X with dH2O.
  4. 10X Tris-Glycine SDS Running Buffer: (#4050) To prepare 1 L 1X running buffer: add 100 ml 10X running buffer to 900 ml dH2O, mix.
  5. 10X Tris-Glycine Transfer Buffer: (#12539) To prepare 1 L 1X Transfer Buffer: add 100 ml 10X Transfer Buffer to 200 ml methanol + 700 ml dH2O, mix.
  6. 10X Tris Buffered Saline with Tween® 20 (TBST): (#9997) To prepare 1 L 1X TBST: add 100 ml 10X TBST to 900 ml dH2O, mix.
  7. Nonfat Dry Milk: (#9999).
  8. Blocking Buffer: 1X TBST with 5% w/v nonfat dry milk; for 150 ml, add 7.5 g nonfat dry milk to 150 ml 1X TBST and mix well.
  9. Wash Buffer: (#9997) 1X TBST.
  10. Bovine Serum Albumin (BSA): (#9998).
  11. Primary Antibody Dilution Buffer: 1X TBST with 5% BSA; for 20 ml, add 1.0 g BSA to 20 ml 1X TBST and mix well.
  12. Biotinylated Protein Ladder Detection Pack: (#7727).
  13. Prestained Protein Marker, Broad Range (Premixed Format): (#7720).
  14. Blotting Membrane and Paper: (#12369) This protocol has been optimized for nitrocellulose membranes. Pore size 0.2 µm is generally recommended.
  15. Secondary Antibody Conjugated to HRP: Anti-rabbit IgG, HRP-linked Antibody (#7074).
  16. Detection Reagent: SignalFire™ ECL Reagent (#6883).

B. Protein Blotting

A general protocol for sample preparation.

  1. Treat cells by adding fresh media containing regulator for desired time.
  2. Aspirate media from cultures; wash cells with 1X PBS; aspirate.
  3. Lyse cells by adding 1X SDS sample buffer (100 µl per well of 6-well plate or 500 µl for a 10 cm diameter plate). Immediately scrape the cells off the plate and transfer the extract to a microcentrifuge tube. Keep on ice.
  4. Sonicate for 10–15 sec to complete cell lysis and shear DNA (to reduce sample viscosity).
  5. Heat a 20 µl sample to 95–100°C for 5 min; cool on ice.
  6. Microcentrifuge for 5 min.
  7. Load 20 µl onto SDS-PAGE gel (10 cm x 10 cm).

    NOTE: Loading of prestained molecular weight markers (#7720, 10 µl/lane) to verify electrotransfer and biotinylated protein ladder (#7727, 10 µl/lane) to determine molecular weights are recommended.

  8. Electrotransfer to nitrocellulose membrane (#12369).

C. Membrane Blocking and Antibody Incubations

NOTE: Volumes are for 10 cm x 10 cm (100 cm2) of membrane; for different sized membranes, adjust volumes accordingly.

I. Membrane Blocking

  1. (Optional) After transfer, wash nitrocellulose membrane with 25 ml TBS for 5 min at room temperature.
  2. Incubate membrane in 25 ml of blocking buffer for 1 hr at room temperature.
  3. Wash three times for 5 min each with 15 ml of TBST.

II. Primary Antibody Incubation

  1. Incubate membrane and primary antibody (at the appropriate dilution and diluent as recommended in the product datasheet) in 10 ml primary antibody dilution buffer with gentle agitation overnight at 4°C.
  2. Wash three times for 5 min each with 15 ml of TBST.
  3. Incubate membrane with Anti-rabbit IgG, HRP-linked Antibody (#7074 at 1:2000) and anti-biotin, HRP-linked Antibody (#7075 at 1:1000–1:3000) to detect biotinylated protein markers in 10 ml of blocking buffer with gentle agitation for 1 hr at room temperature.
  4. Wash three times for 5 min each with 15 ml of TBST.
  5. Proceed with detection (Section D).

D. Detection of Proteins

Directions for Use:

  1. Wash membrane-bound HRP (antibody conjugate) three times for 5 minutes in TBST.
  2. Prepare 1X SignalFire™ ECL Reagent (#6883) by diluting one part 2X Reagent A and one part 2X Reagent B (e.g. for 10 ml, add 5 ml Reagent A and 5 ml Reagent B). Mix well.
  3. Incubate substrate with membrane for 1 minute, remove excess solution (membrane remains wet), wrap in plastic and expose to X-ray film.

* Avoid repeated exposure to skin.

posted June 2005

revised November 2013

protocol id: 10

Western Blot Reprobing Protocol

Reprobing of an existing membrane is a convenient means to immunoblot for multiple proteins independently when only a limited amount of sample is available. It should be noted that for the best possible results a fresh blot is always recommended. Reprobing can be a valuable method but with each reprobing of a blot there is potential for increased background signal. Additionally, it is recommended that you verify the removal of the first antibody complex prior to reprobing so that signal attributed to binding of the new antibody is not leftover signal from the first immunoblotting experiment. This can be done by re-exposing the blot to ECL reagents and making sure there is no signal prior to adding the next primary antibody.

A. Solutions and Reagents

NOTE: Prepare solutions with reverse osmosis deionized (RODI) or equivalently purified water.

  1. Wash Buffer: Tris Buffered Saline with Tween® 20 (TBST-10X) (#9997)
  2. Stripping Buffer: To prepare 100 ml, mix 0.76 g Tris base, 2 g SDS and 700 μl β-mercaptoethanol. Bring to 100 ml with deionized H2O. Adjust pH to 6.8 with HCl.

B. Protocol

  1. After film exposure, wash membrane four times for 5 min each in TBST. Best results are obtained if the membrane is not allowed to dry.
  2. Incubate membrane for 30 min at 50°C in stripping buffer (with slight agitation).
  3. Wash membrane six times for 5 min each in TBST.
  4. (Optional) To assure that the original signal is removed, wash membrane twice for 5 min each with 10 ml of TBST. Incubate membrane with LumiGLO® with gentle agitation for 1 min at room temperature. Drain membrane of excess developing solution. Do not let dry. Wrap in plastic wrap and expose to x-ray film.
  5. Wash membrane again four times for 5 min each in TBST.
  6. The membrane is now ready to reuse. Start detection at the "Membrane Blocking and Antibody Incubations" step in the Western Immunoblotting Protocol.

posted June 2005

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Immunohistochemistry (Paraffin)

A. Solutions and Reagents

NOTE: Prepare solutions with reverse osmosis deionized (RODI) or equivalent grade water.

  1. Xylene.
  2. Ethanol, anhydrous denatured, histological grade (100% and 95%).
  3. Deionized water (dH2O).
  4. Hematoxylin (optional).
  5. Wash Buffer:
    1. 1X Tris Buffered Saline with Tween® 20 (TBST): To prepare 1L 1X TBST add 100 ml 10X Tris Buffered Saline with Tween® 20 (#9997) to 900 ml dH20, mix.
  6. SignalStain® Antibody Diluent (#8112).
  7. Antigen Unmasking Citrate: 10 mM Sodium Citrate Buffer: To prepare 1 L, add 2.94 g sodium citrate trisodium salt dihydrate (C6H5Na3O7•2H2O) to 1 L dH2O. Adjust pH to 6.0.
  8. 3% Hydrogen Peroxide: To prepare 100 ml, add 10 ml 30% H2O2 to 90 ml dH2O.
  9. Blocking Solution: TBST/5% Normal Goat Serum: to 5 ml 1X TBST, add 250 µl Normal Goat Serum (#5425).
  10. Detection System: SignalStain® Boost IHC Detection Reagents (HRP, Rabbit #8114).
  11. Substrate: SignalStain® DAB Substrate Kit (#8059).

B. Deparaffinization/Rehydration

NOTE: Do not allow slides to dry at any time during this procedure.

  1. Deparaffinize/hydrate sections:
    1. Incubate sections in three washes of xylene for 5 min each.
    2. Incubate sections in two washes of 100% ethanol for 10 min each.
    3. Incubate sections in two washes of 95% ethanol for 10 min each.
  2. Wash sections two times in dH2O for 5 min each.

C. Antigen Unmasking

For Citrate: Bring slides to a boil in 10 mM sodium citrate buffer, pH 6.0; maintain at a sub-boiling temperature for 10 min. Cool slides on bench top for 30 min.

D. Staining

  1. Wash sections in dH2O three times for 5 min each.
  2. Incubate sections in 3% hydrogen peroxide for 10 min.
  3. Wash sections in dH2O two times for 5 min each.
  4. Wash sections in wash buffer for 5 min.
  5. Block each section with 100–400 µl blocking solution for 1 hr at room temperature.
  6. Remove blocking solution and add 100–400 µl primary antibody diluted in SignalStain® Antibody Diluent (#8112) to each section. Incubate overnight at 4°C.
  7. Equilibrate SignalStain® Boost Detection Reagent (HRP, Rabbit #8114) to room temperature.
  8. Remove antibody solution and wash sections with wash buffer three times for 5 min each.
  9. Cover section with 1–3 drops SignalStain® Boost Detection Reagent (HRP, Rabbit #8114) as needed. Incubate in a humidified chamber for 30 min at room temperature.
  10. Wash sections three times with wash buffer for 5 min each.
  11. Add 1 drop (30 µl) SignalStain® DAB Chromogen Concentrate to 1 ml SignalStain® DAB Diluent and mix well before use.
  12. Apply 100–400 µl SignalStain® DAB to each section and monitor closely. 1–10 min generally provides an acceptable staining intensity.
  13. Immerse slides in dH2O.
  14. If desired, counterstain sections with hematoxylin per manufacturer’s instructions.
  15. Wash sections in dH2O two times for 5 min each.
  16. Dehydrate sections:
    1. Incubate sections in 95% ethanol two times for 10 sec each.
    2. Repeat in 100% ethanol, incubating sections two times for 10 sec each.
    3. Repeat in xylene, incubating sections two times for 10 sec each.
  17. Mount sections with coverslips.

posted February 2010

revised November 2013

protocol id: 283

Page

Immunofluorescence (Immunocytochemistry)

A. Solutions and Reagents

NOTE: Prepare solutions with reverse osmosis deionized (RODI) or equivalent grade water.

  1. 20X Phosphate Buffered Saline (PBS): (9808) To prepare 1L 1X PBS: add 50 ml 20X PBS to 950 ml dH2O, mix. Adjust pH to 8.0.
  2. Formaldehyde: 16%, methanol free, Polysciences, Inc. (cat# 18814), use fresh and store opened vials at 4°C in dark, dilute in 1X PBS for use.
  3. Blocking Buffer (1X PBS / 5% normal serum / 0.3% Triton™ X-100): To prepare 10 ml, add 0.5 ml normal serum from the same species as the secondary antibody (e.g., Normal Goat Serum (#5425)) and 0.5 mL 20X PBS to 9.0 mL dH2O, mix well. While stirring, add 30 µl Triton™ X-100.
  4. Antibody Dilution Buffer (1X PBS / 1% BSA / 0.3% Triton X-100): To prepare 10 ml, add 30 µl Triton™ X-100 to 10 ml 1X PBS. Mix well then add 0.1 g BSA (9998), mix.
  5. Recommended Fluorochrome-conjugated Anti-Rabbit secondary antibodies:

  6. Prolong® Gold AntiFade Reagent (#9071), Prolong® Gold AntiFade Reagent with DAPI (#8961).

B. Specimen Preparation - Cultured Cell Lines (IF-IC)

NOTE: Cells should be grown, treated, fixed and stained directly in multi-well plates, chamber slides or on coverslips.

  1. Aspirate liquid, then cover cells to a depth of 2–3 mm with 4% formaldehyde diluted in 1X PBS.

    NOTE: Formaldehyde is toxic, use only in a fume hood.

  2. Allow cells to fix for 15 min at room temperature.
  3. Aspirate fixative, rinse three times in 1X PBS for 5 min each.
  4. Proceed with Immunostaining (Section C).

C. Immunostaining

NOTE: All subsequent incubations should be carried out at room temperature unless otherwise noted in a humid light-tight box or covered dish/plate to prevent drying and fluorochrome fading.

  1. Block specimen in Blocking Buffer for 60 min.
  2. While blocking, prepare primary antibody by diluting as indicated on datasheet in Antibody Dilution Buffer.
  3. Aspirate blocking solution, apply diluted primary antibody.
  4. Incubate overnight at 4°C.
  5. Rinse three times in 1X PBS for 5 min each.
  6. Incubate specimen in fluorochrome-conjugated secondary antibody diluted in Antibody Dilution Buffer for 1–2 hr at room temperature in the dark.
  7. Rinse three times in 1X PBS for 5 min each.
  8. Coverslip slides with Prolong® Gold Antifade Reagent (#9071) or Prolong® Gold Antifade Reagent with DAPI (#8961).
  9. For best results, allow mountant to cure overnight at room temperature. For long-term storage, store slides flat at 4°C protected from light.

posted November 2006

revised November 2013

protocol id: 24

Product Usage Information

Application Dilutions
Western Blotting 1:1000
Immunohistochemistry 1:100
Immunofluorescence 1:50

Storage: Supplied in 10 mM sodium HEPES (pH 7.5), 150 mM NaCl, 100 µg/ml BSA, 50% glycerol and less than 0.02% sodium azide. Store at –20°C. Do not aliquot the antibody.

Specificity / Sensitivity

Histone H2A.X (D17A3) XP® Rabbit mAb recognizes endogenous levels of total histone H2A.X protein. This antibody does not cross-react with other histone H2A proteins.


Species Reactivity: Human, Mouse, Rat, Monkey

Source / Purification

Monoclonal antibody is produced by immunizing animals with a synthetic peptide corresponding to residues surrounding Val124 of human histone H2A.X protein.

Histone H2A.X is a variant histone that represents approximately 10% of the total H2A histone proteins in normal human fibroblasts (1). H2A.X is required for checkpoint-mediated cell cycle arrest and DNA repair following double-stranded DNA breaks (1). DNA damage, caused by ionizing radiation, UV-light, or radiomimetic agents, results in rapid phosphorylation of H2A.X at Ser139 by PI3K-like kinases, including ATM, ATR, and DNA-PK (2,3). Within minutes following DNA damage, H2A.X is phosphorylated at Ser139 at sites of DNA damage (4). This very early event in the DNA-damage response is required for recruitment of a multitude of DNA-damage response proteins, including MDC1, NBS1, RAD50, MRE11, 53BP1, and BRCA1 (1). In addition to its role in DNA-damage repair, H2A.X is required for DNA fragmentation during apoptosis and is phosphorylated by various kinases in response to apoptotic signals. H2A.X is phosphorylated at Ser139 by DNA-PK in response to cell death receptor activation, c-Jun N-terminal Kinase (JNK1) in response to UV-A irradiation, and p38 MAPK in response to serum starvation (5-8). H2A.X is constitutively phosphorylated on Tyr142 in undamaged cells by WSTF (Williams-Beuren syndrome transcription factor) (9,10). Upon DNA damage, and concurrent with phosphorylation of Ser139, Tyr142 is dephosphorylated at sites of DNA damage by recruited EYA1 and EYA3 phosphatases (9). While phosphorylation at Ser139 facilitates the recruitment of DNA repair proteins and apoptotic proteins to sites of DNA damage, phosphorylation at Tyr142 appears to determine which set of proteins are recruited. Phosphorylation of H2A.X at Tyr142 inhibits the recruitment of DNA repair proteins and promotes binding of pro-apoptotic factors such as JNK1 (9). Mouse embryonic fibroblasts expressing only mutant H2A.X Y142F, which favors recruitment of DNA repair proteins over apoptotic proteins, show a reduced apoptotic response to ionizing radiation (9). Thus, it appears that the balance of H2A.X Tyr142 phosphorylation and dephosphorylation provides a switch mechanism to determine cell fate after DNA damage.


1.  Yuan, J. et al. (2010) FEBS Lett 584, 3717-24.

2.  Mukherjee, B. et al. (2006) DNA Repair (Amst) 5, 575-90.

3.  Solier, S. et al. (2009) Mol Cell Biol 29, 68-82.

4.  Lu, C. et al. (2006) Mol Cell 23, 121-32.

5.  Lu, C. et al. (2008) FEBS Lett 582, 2703-8.

6.  Cook, P.J. et al. (2009) Nature 458, 591-6.

7.  Rogakou, E.P. et al. (1998) J. Biol. Chem. 273, 5858-5868.

8.  Xiao, A. et al. (2009) Nature 457, 57-62.

9.  Burma, S. et al. (2001) J. Biol. Chem. 276, 42462-42467.

10.  Rogakou, E.P. et al. (1999) J. Cell Biol. 146, 905-916.


Entrez-Gene Id 3014
Swiss-Prot Acc. P16104


For Research Use Only. Not For Use In Diagnostic Procedures.
Cell Signaling Technology® is a trademark of Cell Signaling Technology, Inc.
XP® is a trademark of Cell Signaling Technology, Inc.