Comparison of Hi-C results using in-solution versus in-nucleus ligation

Chromosome conformation capture (3C) and derivative (4C, 5C and Hi-C) methods employ ligation of diluted cross-linked chromatin complexes, intended to favor proximity-dependent, intra-complex ligation. We previously described an alternative Hi-C protocol with ligation in preserved nuclei rather than in solution. Here we directly compare Hi-C methods employing "in-nucleus ligation" and the standard "in-solution ligation". The results show that in-nucleus ligation captures chromatin interactions more consistently over a wider range of distances, and significantly reduces both experimental noise and bias. Thus in-nucleus ligation not only simplifies the experimental procedures, but also produces higher quality data with benefits for the entire range of 3C applications. Overall design: We created Hi-C libraries by two different methods, in-solution ligation and in-nucleus ligation, from two biological replicates each of mouse foetal liver cells (mouse-1 and mouse-2) and human ES cells (human-1 and human-2) or the mixture of these two species. We also sequenced a random ligation library prepared by reversal of the cross-links and purification of the DNA prior to ligation.