ChIP-sequencing (ChIPSeq) – a combination of chromatin immunoprecipitation and next-generation, or parallel, sequencing. The feat was performed “with a speed and precision that goes beyond what has been achieved with previous technologies,” comments University of Washington geneticist Stanley Fields, in an accompanying essay in Science.
hIP is a well-established lab technique to identify those specific sites where proteins latch onto the DNA. Cells are treated with a chemical to fossilize the links between DNA and protein, the chromatin is then isolated, the DNA broken up, and the attached proteins immunoprecipitated. Finally, the DNA stuck to the protein can be released and analyzed. Until now, the most high-throughput application of this technique involved using microarrays containing thousands of gene spots able to identify binding sites for transcription factors and the like.
Next-Generation Sequencing Invades Microarray Turf By Kevin Davies June 14, 2007 | Two new papers unveil a new dimension to commercial next-generation sequencing applications – one that could potentiallypose a threat to more-established microarray technologies. Using theGenome Analyzer from Illumina/Solexa, two groups working independentlyhave been able to map the locations across the genome where a specific
DNA-binding protein latches onto the DNA.
ChIPSeq is a cost-effective alternative to microarray methods, with a significant upside. “Other ultrahigh-throughput sequencing platforms, such as the one from 454 LifeSciences, could also be used to assay ChIP products, but whatever sequencing platform is used, our results indicate that read numbercapacity and input ChIP DNA size are key parameters,” Johnson et al. writes.ChIPSeq might be an order of magnitude cheaper than microarray alternatives, with the eight flow cell lanes in theGenome Analyzer offering excellent design flexibility. Fewer materialsare required, and the method can be applied to any organism – it is not restricted to available gene arrays.
The advantages of ChIPSeq over ChIP-chip include the ability to interrogate the entire genome rather than just the genesrepresented on a microarray. (For example, Johnson et al. point out thata similar experiment using Affymetrix-style microarrays would requireroughly 1 billion features per array.) There is also the benefit of
sidestepping known hybridization complications with microarrayplatforms. “Perhaps most usefully,” writes Fields, “ChIPSeq canimmediately be applied to any of those [available] genomes, rather thanonly those for which microarrays are available.”
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