ChIP-seq profile of RPA in B upon HU treatment

In this study, we map sites of replication initiation and breakage in primary cells at high resolution under conditions of replication stress. We show that replication initiates between transcribed genes within nucleosome-depleted structures established by long asymmetrical poly(dA:dT) tracts flanking the initiation site. Paradoxically, large (>20 bp) homopolymeric (dA/dT) tracts are also preferential sites of polar replication fork stalling and collapse. We propose that the evolutionary expansion of poly(dA:dT) tracts in eukaryotic genomes serves to promote replication initiation, but at the cost of increasing chromosome fragility. Overall design: ChIP-seq profile of RPA in B upon HU treatment

本研究在复制应激条件下，以高分辨率绘制了原代细胞内复制起始与染色体断裂位点的图谱。
我们发现，复制起始发生于转录基因之间、由起始位点侧翼的长不对称聚(dA:dT)序列（poly(dA:dT) tracts）所形成的核小体缺失结构内部。
矛盾的是，长度大于20 bp的同源多聚(dA/dT)序列同样是极性复制叉停滞与崩解的偏好性位点。
我们提出，真核基因组中聚(dA:dT)序列的进化扩张虽可促进复制起始，但却以增加染色体脆性为代价。
实验整体设计：经羟基脲（HU）处理的B细胞内复制蛋白A（RPA）的染色质免疫沉淀测序（ChIP-seq）图谱。