Epigenetically-inherited centromere and neocentromere DNA replicates earliest in S-phase

In order to address the replication timing of the centromeres in yeast Candida albicans, we have determined at high temporal and spatial resolution its genome-wide DNA replication timing profile. This was done by sorting S- and G1-phase cells by FACS and hybridizing DNA from both fractions onto genomic tiling arrays. Data was normalized, organized by chromosomal positition, and smoothed. Replication timing is inferred from the DNA copy number along the chromosome with data peaks corresponding to predicted origins of DNA replication. We observe that the centromeric loci coincide with replication origins that are the first to replicate on each chromosome. We further analyzed replication timing in strain 9929s, in which the centromere of chromosome 5 was deleted and a neocentromere has formed at a distant location. A replication origin, again the first to replicate, appeared at the site of neocentromere formation. We conclude that centromeres cause their own early and distinct DNA replication timing. Four repeats of the wild type strain (SC5314) and two repeats of strain YJB9929s, S phase- vs G1 phase-cell DNA with different Cy dyes for each. The supplementary file 'GSE17963_final_data.txt' contains the fully processed replication timing data; its contents is described in 'GSE17963_readme.txt'.

为解析白色念珠菌（Candida albicans）着丝粒的DNA复制时序，我们以高时空分辨率测定了其全基因组DNA复制时序图谱。本研究通过荧光激活细胞分选术（FACS）分离S期与G1期细胞，并将两个组分的DNA与基因组叠瓦式芯片（genomic tiling arrays）进行杂交。随后对所得数据开展标准化处理、按染色体位置排序并完成平滑化操作。我们基于染色体上的DNA拷贝数推断复制时序，数据峰值对应预测的DNA复制起始位点。研究观察到，着丝粒位点与各染色体上率先起始复制的复制起始位点相重合。我们进一步对菌株9929s开展了复制时序分析：该菌株的5号染色体着丝粒已被删除，并在远端区域形成了新着丝粒（neocentromere）。此时在新着丝粒形成的位点，再次出现了一个率先起始复制的复制起始位点。综上，我们得出结论：着丝粒可诱导自身发生早期且特异的DNA复制。野生型菌株SC5314共设置4次生物学重复，菌株YJB9929s共设置2次生物学重复，每组的S期与G1期细胞DNA分别采用不同的Cy染料标记。补充文件"GSE17963_final_data.txt"包含完整处理后的复制时序数据，其内容说明详见"GSE17963_readme.txt"。