Chromosome segregation requires both compaction and disentanglement of sister chromatids. We describe SisterC, a chromosome conformation capture assay that distinguishes interactions between and along identical sister chromatids. SisterC employs 5-bromo-2′-deoxyuridine (BrdU) incorporation during S-phase to label newly replicated strands, followed by Hi-C and then the destruction of 5-bromodeoxyuridine-containing strands via Hoechst/ultraviolet treatment. After sequencing of the remaining intact strands, this allows assignment of Hi-C products as inter- and intra-sister interactions based on the strands that reads are mapped to. We performed SisterC on mitotic Saccharomyces cerevisiae cells. We find precise alignment of sister chromatids at centromeres. Along arms, sister chromatids are less precisely aligned, with inter-sister connections every ~35 kilobase (kb). Inter-sister interactions occur between cohesin binding sites that are often offset by 5 to 25 kb. Along sister chromatids, cohesin results in the formation of loops of up to 50 kb. SisterC allows study of the complex interplay between sister chromatid compaction and their segregation during mitosis.

染色体分离需要姐妹染色单体的压实和解缠。我们描述了SisterC，这是一种染色体构象捕获测定法，可区分相同姐妹染色单体之间以及沿着同一姐妹染色单体之间的相互作用。SisterC在S期使用5-溴2'-脱氧尿苷（BrdU）掺入以标记新复制的链，然后进行Hi-C标记，然后通过Hoechst /紫外线处理破坏含5-溴脱氧尿苷的链。在对剩余的完整链进行测序之后，这允许基于读取的链将Hi-C产物分配为姐妹间和姐妹内相互作用。我们对有丝分裂的酿酒酵母进行了SisterC细胞。我们发现着丝粒姐妹染色单体的精确比对。沿着臂，姐妹染色单体的排列较不精确，姐妹之间的连接每35 kb（kb）。姐妹之间的相互作用发生在黏附素结合位点之间，该位点之间通常相距5到25 kb。沿着姐妹染色单体，粘着蛋白导致形成高达50 kb的环。SisterC可以研究姐妹染色单体压实与其在有丝分裂期间的分离之间的复杂相互作用。