• Product nameAnti-p21 antibody [CP74]
    See all p21 primary antibodies
  • Description
    Mouse monoclonal [CP74] to p21
  • SpecificityCo-precipitates cdk4
  • Tested applicationsSuitable for: WB, IP, IHC-P, Flow Cytmore details
  • Species reactivity
    Reacts with: Rat, Human
  • Immunogen

    Recombinant full length Human protein

  • EpitopeN terminal residues 1-80.
  • Positive control
    • Raji, PC12 cells; Colon carcinoma tissue.



Our Abpromise guarantee covers the use of ab80633 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
WB Use a concentration of 1 - 2 µg/ml. Predicted molecular weight: 18 kDa.
IP Use at 2 µg/mg of lysate. Native verified. Use Protein A.
IHC-P Use a concentration of 5 µg/ml. Perform heat mediated antigen retrieval before commencing with IHC staining protocol.
Flow Cyt Use 1µg for 106 cells. ab170192-Mouse monoclonal IgG2b, is suitable for use as an isotype control with this antibody.


  • 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 [CP74] images

  • IHC image of ab80633 staining in Breast Cancer formalin fixed paraffin embedded tissue section, performed on a Leica BondTM system using the standard protocol F. The section was pre-treated using heat mediated antigen retrieval with sodium citrate buffer (pH6, epitope retrieval solution 1) for 20 mins. The section was then incubated with ab80633, 5µg/ml, for 15 mins at room temperature and detected using an HRP conjugated compact polymer system. DAB was used as the chromogen. The section was then counterstained with haematoxylin and mounted with DPX.

    For other IHC staining systems (automated and non-automated) customers should optimize variable parameters such as antigen retrieval conditions, primary antibody concentration and antibody incubation times.

  • Predicted band size : 18 kDa

    Image from Linley AJ et al, J Biol Chem. 2012 Apr 20;287(17):13633-43. Epub 2012 Mar 5, Fig 3. DOI 10.1074/jbc.M111.308973 April 20, 2012 The Journal of Biological Chemistry, 287, 13633-13643.

    ab80633 used at a 1/250 dilution for Western Blot.
    Human cancer cells were collected, washed with 1× PBS, lysed in 1× solution containing 50 mm Tris-HCl (pH 6.8), 100 mm dithiothreitol, 2% (w/v) SDS, 0.1% (w/v) bromphenol blue, and 10% (v/v) glycerol and loaded on Tris/glycine SDS-polyacrylamide gels. Proteins were separated alongside a molecular weight marker. Protein bands were transferred onto PVDF membranes. Membranes were blocked with 10% milk/TBS solution with 0.05% Tween 20 containing sodium orthovanadate and sodium fluoride. Following TBS solution with 0.05% Tween 20 washes, membranes were incubated with primary antibodies (in blocking solution) at 4 °C overnight followed by washing and incubation with secondary antibodies for 1 hour at room temperature.
  • Overlay histogram showing HeLa cells stained with ab80633 (red line). The cells were fixed with 4% paraformaldehyde (10 min) and then permeabilized with 0.1% PBS-Tween for 20 min. The cells were then incubated in 1x PBS / 10% normal goat serum / 0.3M glycine to block non-specific protein-protein interactions followed by the antibody (ab80633, 1µg/1x106 cells) for 30 min at 22ºC. The secondary antibody used was anti-mouse DyLight® 488 (ab96879) at 1/500 dilution for 30 min at 22ºC. Isotype control antibody (black line) was mouse IgG2b [PLPV219] (ab91366, 2µg/1x106 cells) used under the same conditions. Unlabelled sample (blue line). Acquisition of >5,000 events were collected using a 20mW Argon ion laser (488nm) and 525/30 bandpass filter. This antibody gave a positive signal in HeLa cells fixed with 80% methanol (5 min)/permeabilized with 0.1% PBS-Tween for 20 min used under the same conditions.

References for Anti-p21 antibody [CP74] (ab80633)

This product has been referenced in:
  • Kilarkaje N & Al-Bader MM Diabetes-Induced Oxidative DNA Damage Alters p53-p21CIP1/Waf1 Signaling in the Rat Testis. Reprod Sci N/A:N/A (2014). WB ; Rat . Read more (PubMed: 24828139) »
  • Linley AJ  et al. The Helicase HAGE Expressed by Malignant Melanoma-Initiating Cells Is Required for Tumor Cell Proliferation in Vivo. J Biol Chem 287:13633-43 (2012). WB ; Human . Read more (PubMed: 22393060) »

See all 2 Publications for this product

Product Wall

Application Immunohistochemistry (Formalin/PFA-fixed paraffin-embedded sections)
Sample Human Tissue sections (endometriosis)
Antigen retrieval step Heat mediated - Buffer/Enzyme Used: Citrat-Buffer pH 6,0
Permeabilization No
Specification endometriosis
Blocking step Serum as blocking agent for 30 minute(s) · Concentration: 3% · Temperature: 20°C
Fixative Formaldehyde

Abcam user community

Verified customer

Submitted Jan 13 2017

Application Immunohistochemistry (Formalin/PFA-fixed paraffin-embedded sections)
Blocking step BSA as blocking agent for 15 minute(s) · Concentration: 2% · Temperature: 37°C
Antigen retrieval step Heat mediated
Sample Rat Tissue sections (Testis)
Specification Testis
Permeabilization No
Fixative Bouin's fluid

Dr. Kilarkaje Narayana

Verified customer

Submitted Jul 07 2014