Analikwu Brian T, Deshayes Alice, van der Torre Jaco, Guérin Thomas M, Katan Allard J, Béneut Claire, Barth Roman, Phipps Jamie, Scolari Vittore, Veaute Xavier, Busso Didier, Dubrana Karine, Mattarocci Stefano, Dekker Cees, Marcand Stéphane
Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands.
Université Paris-Saclay, Université Paris-Cité, CEA, Inserm, Institut de Biologie François Jacob, UMR Stabilité Génétique Cellules Souches et Radiations, Fontenay-aux-Roses, France.
Cell Rep. 2025 Jul 22;44(7):115900. doi: 10.1016/j.celrep.2025.115900. Epub 2025 Jun 24.
DNA loop extrusion by SMC proteins is a key process underlying chromosomal organization. It is unknown how loop extruders interact with telomeres where DNA is densely covered with proteins. Using complementary in vivo and in vitro single-molecule approaches, we study how loop-extruding condensin interacts with Rap1, the telomeric DNA-binding protein of Saccharomyces cerevisiae. We show that dense linear Rap1 arrays can completely halt DNA loop extrusion, with a blocking efficiency depending on the array length and the DNA gap size between proteins. In anaphase cells, dense Rap1 arrays are found to accumulate condensin and to cause a local chromatin decompaction, as monitored with a microscopy-based approach, with direct implications for the resolution of dicentric chromosomes produced by telomere fusions. Our findings show that linear arrays of DNA-bound proteins can efficiently halt DNA loop extrusion by SMC proteins, which may impact cellular processes from telomere functions to transcription and DNA repair.
SMC蛋白介导的DNA环挤压是染色体组织形成的关键过程。目前尚不清楚环挤压蛋白如何与端粒相互作用，因为端粒上的DNA被蛋白质密集覆盖。我们使用互补的体内和体外单分子方法，研究环挤压蛋白凝聚素如何与酿酒酵母的端粒DNA结合蛋白Rap1相互作用。我们发现，密集的线性Rap1阵列可以完全阻止DNA环挤压，其阻断效率取决于阵列长度和蛋白质之间的DNA间隙大小。在后期细胞中，通过基于显微镜的方法监测发现，密集的Rap1阵列会积累凝聚素并导致局部染色质解压缩，这对端粒融合产生的双着丝粒染色体的分辨率有直接影响。我们的研究结果表明，与DNA结合的蛋白质线性阵列可以有效地阻止SMC蛋白介导的DNA环挤压，这可能会影响从端粒功能到转录和DNA修复的细胞过程。
