A role for condensin-mediator interaction in mitotic chromosomal organization

Eukaryotic genomes are organized by condensin into 3D chromosomal architectures suitable for chromosomal segregation during mitosis. However, molecular mechanisms underlying the condensin-mediated chromosomal organization remain largely unclear. Here, we investigate the role of newly identified interaction between the Cnd1 condensin and Pmc4 mediator subunits in fission yeast, Schizosaccharomyces pombe. We develop a condensin mutation, cnd1-K658E, that impairs the condensin-mediator interaction and find that this mutation diminishes condensin-mediated chromatin domains during mitosis and causes chromosomal segregation defects. The condensin-mediator interaction is involved in recruiting condensin to highly transcribed genes and mitotically activated genes, the latter of which demarcate condensin-mediated domains. Furthermore, this study predicts that mediator-driven transcription of mitotically activated genes contributes to forming domain boundaries via phase separation. This study provides a novel insight into how genome-wide gene expression during mitosis is transformed into the functional chromosomal architecture suitable for chromosomal segregation. O_FIG O_LINKSMALLFIG WIDTH=189 HEIGHT=200 SRC="FIGDIR/small/600663v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@488ab5org.highwire.dtl.DTLVardef@8a7a73org.highwire.dtl.DTLVardef@16d416eorg.highwire.dtl.DTLVardef@1e2d3db_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG In BriefMitotic chromosomes are organized by condensin into an architecture suitable for their segregation, although molecular mechanisms underlying how condensin assembles the functional chromosomal architecture remain unclear. This study with the fission yeast model organism shows that the protein interaction between condensin and mediator is involved in chromosomal segregation by forming a mitotic chromosomal architecture. A similar mechanism involving the condensin-mediator interaction is likely conserved in human cells, implying the evolutionary conservation of this mechanism. HighlightsO_LIThe Cnd1 condensin subunit interacts with the Pmc4 mediator component in fission yeast. C_LIO_LIThe condensin-mediator interaction is required to recruit condensin to highly transcribed and mitotically activated genes. C_LIO_LIThe condensin-mediator interaction is required to form chromatin domains during mitosis. C_LIO_LIMediator participates in the boundary formation of mitotic chromatin domains. C_LI