Condensin II collaborates with cohesin to establish and maintain interphase chromosome territories

Abstract

Despite the well-established role of condensin II in mitotic chromosome assembly, its function in interphase chromosome organization remains poorly understood. Here, we applied multiscale fluorescence in situ hybridization (FISH) techniques to human cell lines engineered for single or double depletion of condensin II and cohesin, and examined their functional interplay at two distinct stages of the cell cycle. Our results demonstrate that a functional "handover" from condensin II to cohesin during the mitosis-to-G1 transition is critical for establishing chromosome territories (CTs) in the newly assembling nucleus. During G2 phase, condensin II and cohesin cooperate to maintain global CT morphology, although they act at different genomic scales. Strikingly, double depletion of both complexes causes CTs to collapse and accumulate abnormally at the nucleolar periphery. Based on these findings, we will discuss how the condensin and cohesin complexes act in an orderly and cooperative manner to orchestrate chromatin dynamics across genomic scales, thereby supporting higher-order chromosome organization throughout the cell cycle.