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Chromatin Immunoprecipitation (ChIP) Troubleshooting Guide

  • How to troubleshoot low or no signal in ChIP assay?

    Low or no ChIP signal is most commonly caused by insufficient chromatin input, poor antibody performance, over-crosslinking with formaldehyde, overly stringent washing, or inefficient chromatin shearing. To improve ChIP signal, ensure sufficient chromatin input (≥25 μg per IP), optimize fixation and shearing conditions, and verify that the antibody and Protein A/G/L beads are compatible for immunoprecipitation.

     

    Common causes of low or no signal in ChIP assay and how to and troubleshooting solutions
      Possible Causes What You Can Do
    Not enough cells/chromatin Add enough chromatin for each IP experiment. We suggest using at least 25 μg of chromatin for each IP.
    Incorrect Protein A/G/L used
    Make sure that the Protein A/G/L beads are capable of binding to the antibody subclass being used.
    Cross-linking process too long
    		 Over Cross-linking with formaldehyde might mask the antibody binding sites and reduce antibody binding ability. It is advisable to optimize the cross-linking steps by using different concentration of formaldehyde or reducing cross-linking time.
    Not enough antibody
    		 Titre antibody amount used for each IP to determine the optimal condition. Up to 10ug of antibody can be used for each IP experiment.
    Washes too stringent Reduce the number of washes. Reduce salt concentration in the wash buffer.
    Antibody not capable of
    immunoprecipitation    		 Try a different antibody. Try polyclonal antibody if monoclonal antibody does not work well.
    The chromatin size might be too small Make sure that the shearing condition is not too harsh which might results in fragments of DNA smaller than what the primers are able to amplify.
    Incomplete elution from the Protein
    A/G/L beads    		 Incubate beads in elution buffer at 65°C with frequent mixing.

     

  • How to fix a positive signal in ChIP no template control (NTC)?

    A positive signal in a ChIP no template control (NTC) usually indicates PCR reagent contamination. Prepare fresh solutions from stock to resolve this issue.

     

    Cause and solution for positive signal in ChIP no template control
      Possible Cause What You Can Do
    PCR reagents may be contaminated Prepare new solutions from stock.

  • How to reduce high background in the negative control of a ChIP assay?

    High background in ChIP negative controls usually indicates non-specific binding or technical contamination during the immunoprecipitation or PCR steps. The issue is most commonly caused by insufficient washing, antibody or bead-related non-specific interactions, or contaminated reagents.

    Common causes of high background in ChIP assay and how to reduce nonspecific signal
      Possible Causes What You Can Do
    Inadequate washing
    Use a more stringent washing buffer. Try to  use a high salt washing buffer or increase the number of washes.
    Non specific binding to Protein A,G or L
    		 Include a pre-clear step by incubating lysate with Protein A/G/L agarose beads.
    Too much DNA template added
    to the PCR reaction, or too many
    cycles of amplification
    		 Add less DNA template or reduce the number of cycles of amplification.  Alternatively, real-time PCR can be used for the detection of ChIPed DNA products.
    Buffers may be contaminated Use freshly prepared lysis or wash buffers.