ChIP-Seq: Chromatin Immunoprecipitation Principles & Protocol

critical

No Product in Histone H3 Positive Control IP

Positive control Histone H3-IP with RPL30 primer set produces no PCR product, indicating fundamental problems with IP procedure or elution.

💡 4 · ✓ 4

critical

No or Minimal PCR Product in Input Control

Input chromatin PCR reactions produce no product or very little product, indicating problems with DNA quantity, PCR conditions, or primer design.

💡 5 · ✓ 5

severe

High Background Signal in Non-Specific Antibody Controls

ChIP experiments show elevated signal levels in non-specific antibody controls (IgG or no-antibody controls), making it difficult to distinguish true binding events from background noise. The signal-to-noise ratio is poor, compromising data interpretation.

💡 5 · ✓ 6

severe

Poor Chromatin Quality from Crosslinking or Fragmentation Issues

ChIP-seq shows high background noise with poorly defined peaks. DNA fragment size distribution is inconsistent, resulting in low resolution across genomic regions.

💡 4 · ✓ 5

severe

Poor Library Quality from Overamplification or Contamination

ChIP-seq data shows elevated background noise, high duplication rates, and presence of nonspecific fragments. Peak resolution is reduced with diffuse signal patterns.

💡 4 · ✓ 5

severe

Low Signal from Using N-ChIP for Weak DNA-Binding Proteins

Consistently low or absent signal when studying transcription factors or chromatin-associated proteins using native ChIP (N-ChIP). Histone ChIP experiments work well in the same laboratory.

💡 4 · ✓ 4

severe

High Background Signal Due to Insufficient ChIP Washing

Elevated background signal appears across all samples including negative controls, with nonspecific amplification in qPCR. PCR products may show multiple bands or high Ct values in control regions.

💡 4 · ✓ 5

severe

Low ChIP Signal Due to Chromatin Over-Fragmentation

Low or absent signal in ChIP experiment despite proper antibody and starting material. Chromatin fragments are smaller than 500 bp after sonication or enzymatic digestion.

💡 4 · ✓ 4

severe

No DNA Amplification in ChIP Samples

No PCR product is detected in ChIP samples by qPCR or gel electrophoresis. Ct values fail to appear or remain above threshold, and no visible bands are observed on gels.

💡 5 · ✓ 6

severe

Chromatin Over-Fragmentation to Mono-Nucleosome Length

More than 80% of DNA fragments are shorter than 500 bp, resulting in diminished PCR signal especially for amplicons >150 bp, and potential disruption of chromatin integrity and antibody epitopes.

💡 4 · ✓ 4

severe

No Product in Experimental Antibody IP

Experimental antibody-IP PCR reaction produces no product while positive control H3-IP works, indicating antibody-specific or target-specific issues.

💡 5 · ✓ 5

severe

Fragmented Chromatin Concentration Below Required Threshold

DNA concentration of chromatin preparation is insufficient for ChIP, falling below the recommended 50 µg/ml or unable to provide 5-10 µg per IP reaction.

💡 4 · ✓ 4

severe

Equivalent Signal in Negative IgG and Positive H3 Controls

Quantity of PCR product in negative control Rabbit IgG-IP equals that in positive control Histone H3-IP, indicating high non-specific binding or PCR over-amplification.

💡 5 · ✓ 5

moderate

Loss of Specific Signal Due to Overly Stringent Wash Conditions

Low signal at expected target regions while background is also very low. Positive control regions show reduced signal compared to expected levels.

💡 4 · ✓ 4

moderate

Low ChIP Signal from Ineffective Cell Lysis

Overall low signal with visible cell clumps or debris in lysate. Chromatin yield is lower than expected based on starting cell number.

💡 4 · ✓ 4

moderate

Insufficient Sequencing Depth for Target Type

ChIP-seq produces broad, noisy peaks with poor statistical confidence. Peaks are difficult to call reliably, especially for diffuse histone marks or low-abundance transcription factors.

💡 4 · ✓ 5