Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA.
Nature. 2024 Oct;634(8036):1221-1228. doi: 10.1038/s41586-024-07999-5. Epub 2024 Oct 2.
A central feature of meiosis is the pairing of homologous maternal and paternal chromosomes ('homologues') along their lengths. Recognition between homologues and their juxtaposition in space is mediated by axis-associated recombination complexes. Also, pairing must occur without entanglements among unrelated chromosomes. Here we examine homologue juxtaposition in real time by four-dimensional fluorescence imaging of tagged chromosomal loci at high spatio-temporal resolution in budding yeast. We discover that corresponding loci come together from a substantial distance (1.8 µm) and complete pairing in a very short time, about 6 min (thus, rapid homologue juxtaposition or RHJ). Homologue loci first move rapidly together (in 30 s, at speeds of roughly 60 nm s) into an intermediate stage corresponding to canonical 400 nm axis coalignment. After a short pause, crossover/non-crossover differentiation (crossover interference) mediates a second short, rapid transition that ultimately gives close pairing of axes at 100 nm by means of synaptonemal complex formation. Furthermore, RHJ (1) occurs after chromosomes acquire prophase chromosome organization, (2) is nearly synchronous over thirds of chromosome lengths, but (3) is asynchronous throughout the genome. Finally, cytoskeleton-mediated movement is important for the timing and distance of RHJ onset and for ensuring its normal progression. General implications for local and global aspects of pairing are discussed.
减数分裂的一个核心特征是同源的母本和父本染色体（“同源染色体”）沿着它们的长度配对。同源染色体之间的识别和它们在空间中的并置是由轴相关的重组复合物介导的。此外，配对必须在不缠绕无关染色体的情况下发生。在这里，我们通过在芽殖酵母中以高时空分辨率对标记的染色体位点进行四维荧光成像，实时检查同源染色体的并置。我们发现，相应的位点从相当远的距离（1.8 μm）聚集在一起，并在很短的时间内（约 6 分钟）完成配对，因此，快速同源染色体聚集或 RHJ。同源染色体首先快速地一起移动（在 30 秒内，速度约为 60nm/s）进入与经典的 400nm 轴对准相对应的中间阶段。短暂停顿后，交叉/非交叉分化（交叉干扰）介导了第二个短暂的快速转变，最终通过联会复合体的形成实现了 100nm 的紧密配对。此外，RHJ（1）发生在染色体获得前期染色体组织之后，（2）在染色体长度的三分之一处几乎是同步的，但（3）在整个基因组中是异步的。最后，细胞骨架介导的运动对于 RHJ 起始的时间和距离以及确保其正常进展很重要。讨论了对配对的局部和全局方面的一般影响。
