• Product nameAnti-p21 antibody [WA-1]
    See all p21 primary antibodies
  • Description
    Mouse monoclonal [WA-1] to p21
  • Specificityp21 protein [wild-type p53-activated fragment 1 (WAF-1) or Cdk-interacting protein (CIP1)].
  • Tested applicationsSuitable for: ICC/IF, IHC-Fr, ELISA, WBmore details
  • Species reactivity
    Reacts with: Rat, Human, Monkey
  • Immunogen

    Full length native protein (purified) (Human).

  • General notesThis antibody was advertised as suitable for use in immunohistochemistry on paraffin-embedded sections (retrieval of antigen by heating in citrate buffer in microwave oven is essential). However, please be aware that customer feedback debates whether it is suitable in this application and we would be interested to hear from any other researchers who have tested the antibody in this technique.



Our Abpromise guarantee covers the use of ab7903 in the following tested applications.

The application notes include recommended starting dilutions; optimal dilutions/concentrations should be determined by the end user.

Application Abreviews Notes
ICC/IF 1/100. PubMed: 18824567For PMID 21788368, cells were fixed in methanol.
IHC-Fr 1/100. PubMed: 18824567
ELISA Use at an assay dependent concentration.
WB Use at an assay dependent concentration. Predicted molecular weight: 18 kDa.


  • FunctionMay be the important intermediate by which p53/TP53 mediates its role as an inhibitor of cellular proliferation in response to DNA damage. Binds to and inhibits cyclin-dependent kinase activity, preventing phosphorylation of critical cyclin-dependent kinase substrates and blocking cell cycle progression. Functions in the nuclear localization and assembly of cyclin D-CDK4 complex and promotes its kinase activity towards RB1. At higher stoichiometric ratios, inhibits the kinase activity of the cyclin D-CDK4 complex.
  • Tissue specificityExpressed in all adult human tissues, with 5-fold lower levels observed in the brain.
  • Sequence similaritiesBelongs to the CDI family.
  • DomainThe PIP-box K+4 motif mediates both the interaction with PCNA and the recuitment of the DCX(DTL) complex: while the PIP-box interacts with PCNA, the presence of the K+4 submotif, recruits the DCX(DTL) complex, leading to its ubiquitination.
    The C-terminal is required for nuclear localization of the cyclin D-CDK4 complex.
  • Post-translational
    Phosphorylation of Thr-145 by Akt or of Ser-146 by PKC impairs binding to PCNA. Phosphorylation at Ser-114 by GSK3-beta enhances ubiquitination by the DCX(DTL) complex.
    Ubiquitinated by MKRN1; leading to polyubiquitination and 26S proteasome-dependent degradation. Ubiquitinated by the DCX(DTL) complex, also named CRL4(CDT2) complex, leading to its degradation during S phase or following UV irradiation. Ubiquitination by the DCX(DTL) complex is essential to control replication licensing and is PCNA-dependent: interacts with PCNA via its PIP-box, while the presence of the containing the 'K+4' motif in the PIP box, recruit the DCX(DTL) complex, leading to its degradation.
  • Cellular localizationCytoplasm. Nucleus.
  • Information by UniProt
  • Database links
  • Alternative names
    • CAP20 antibody
    • CDK-interacting protein 1 antibody
    • CDKI antibody
    • CDKN1 antibody
    • Cdkn1a antibody
    • CDN1A_HUMAN antibody
    • CIP1 antibody
    • Cyclin Dependent Kinase Inhibitor 1A antibody
    • Cyclin-dependent kinase inhibitor 1 antibody
    • Cyclin-dependent kinase inhibitor 1A (P21) antibody
    • Cyclin-dependent kinase inhibitor 1A (p21, Cip1) antibody
    • DNA Synthesis Inhibitor antibody
    • MDA-6 antibody
    • MDA6 antibody
    • Melanoma differentiation-associated protein 6 antibody
    • Melanoma differentiation-associated protein antibody
    • p21 antibody
    • P21 protein antibody
    • p21CIP1 antibody
    • p21Cip1/Waf1 antibody
    • p21WAF antibody
    • PIC1 antibody
    • SDI1 antibody
    • SLC12A9 antibody
    • WAF1 antibody
    • Wild type p53 activated fragment 1 (WAF1) antibody
    • Wild type p53 activated fragment 1 antibody
    • Wildtype p53-activated fragment 1 antibody
    see all

Anti-p21 antibody [WA-1] images

  • Immunocytochemistry/ Immunofluorescence analysis of human primary fibroblasts labeling p21 with ab7903 (green). Actin cytoskeleton decorated by phalloidin (red) and cell nuclei stained with DAPI (blue). 

  • Immunohistochemistry (Formalin/PFA-fixed paraffin-embedded sections) analysis of human colon carcinoma tissue sections labeling p21 with ab7903.

References for Anti-p21 antibody [WA-1] (ab7903)

This product has been referenced in:
  • Geißler S  et al. In serum veritas-in serum sanitas? Cell non-autonomous aging compromises differentiation and survival of mesenchymal stromal cells via the oxidative stress pathway. Cell Death Dis 4:e970 (2013). WB ; Rat . Read more (PubMed: 24357801) »
  • Krzywicka-Racka A & Sluder G Repeated cleavage failure does not establish centrosome amplification in untransformed human cells. J Cell Biol 194:199-207 (2011). ICC/IF ; Human . Read more (PubMed: 21788368) »

See all 4 Publications for this product

Product Wall

Thank you for confirming these details.

I am sorry that you did not receive the proper volume of ab7903. I noticed that you also had a shortage on ab24584 and reported this to us on August 8th. I have flagged up your account so that all vial...

Read More

I am sorry to hear that you are having problems with ab7903. There was a previous complaint concerning this antibody (a different batch, however) where the customer reported seeing bands of higher molecular weights. Because of this report and now yours...

Read More

detection of soluble p21. Antigen (included standard concentration range of p21) coated on plates. Detection by antibody WA-1 and by secondary HRP-conjugate. Chromogen visualization. In house ELISA test (not published). Corellated to commercial ELISA...

Read More

1 unit of ab7960 will be shipped to you on Monday of next week. No further effort is needed on your part in order to receive the replacement, but I would be most grateful if you could let me know how you get on with this antibody.

Our supplier has tested this antibody in ELISA with recombinant p21 and by Western Blotting in MCF-7 cells. The evidence for its suitability for use in IHC comes from the reference on the datasheet which it seems is a poster abstract. This is unsatisfa...

Read More

We have no images available, but p21 demonstrates nuclear staining. To the best of our knowledge, no further cross-reactivity data has been established. Ab7960, Rabbit polyclonal to p21, is suitable for IHC on frozen sections. This antibody shou...

Read More

Whole p21 was used as the immunogen and the exact epitope recognised by this antibody has not been determined. This antibody has not specifically been tested for cross-reactivity in hamster, but it is expected to cross-react with p21 from other mammals.

Read More

Thank you for your feedback. I note from the datasheets that this antibody has been shown to be suitable for use with human tissue in immunohistochemistry with formalin-fixed paraffin-embedded sections. It has not been tested for species cross reactivi...

Read More

This antibody has been tested on paraffin embedded sections in human tissue, but has not yet been tested with mouse tissue. However, we do expect that it would work. We give a 20 dollar Amazon reward voucher for reviews of antibodies with new informa...

Read More

To our knowledge, this antibody has not been specifically used for this purpose. However, it has been shown to work successfully on on paraffin-embedded sections (please see datasheet for more details). The immunogen was human p21 protein and the antib...

Read More

1-10 of 11 Abreviews or Q&A