School of Life Sciences, University of Nottingham, Queen's Medical Centre, NG7 2UH, UK.
Virginia Tech, Department of Biological Sciences, Fralin Life Sciences Institute, 1015 Life Science Circle, Blacksburg, VA 24061, USA.
Nucleic Acids Res. 2022 Jan 11;50(1):579-596. doi: 10.1093/nar/gkab1219.
We have used chromosome engineering to replace native centromeric DNA with different test sequences at native centromeres in two different strains of the fission yeast Schizosaccharomyces pombe and have discovered that A + T rich DNA, whether synthetic or of bacterial origin, will function as a centromere in this species. Using genome size as a surrogate for the inverse of effective population size (Ne) we also show that the relative A + T content of centromeric DNA scales with Ne across 43 animal, fungal and yeast (Opisthokonta) species. This suggests that in most of these species the A + T content of the centromeric DNA is determined by a balance between selection and mutation. Combining the experimental results and the evolutionary analyses allows us to conclude that A + T rich DNA of almost any sequence will function as a centromere in most Opisthokonta species. The fact that many G/C to A/T substitutions are unlikely to be selected against may contribute to the rapid evolution of centromeric DNA. We also show that a neo-centromere sequence is not simply a weak version of native centromeric DNA and suggest that neo-centromeres require factors either for their propagation or establishment in addition to those required by native centromeres.
我们利用染色体工程，在裂殖酵母 Schizosaccharomyces pombe 的两个不同菌株的天然着丝粒处，用不同的测试序列替换了天然着丝粒 DNA，发现富含 A+T 的 DNA，无论是合成的还是源自细菌的，都可以在该物种中作为着丝粒发挥作用。我们还使用基因组大小作为有效种群大小 (Ne) 的倒数的替代物，表明在跨越 43 种动物、真菌和酵母（后生动物）物种的着丝粒 DNA 中，A+T 含量与 Ne 呈负相关。这表明在大多数这些物种中，着丝粒 DNA 的 A+T 含量是由选择和突变之间的平衡决定的。将实验结果和进化分析相结合，使我们能够得出结论，即富含 A+T 的 DNA 几乎任何序列都可以在后生动物物种中作为着丝粒发挥作用。事实上，许多 G/C 到 A/T 的取代不太可能被选择所反对，这可能有助于着丝粒 DNA 的快速进化。我们还表明，新着丝粒序列不仅仅是天然着丝粒 DNA 的弱版本，并表明新着丝粒需要在天然着丝粒所需的因素之外，才能进行传播或建立。
