Two-step regulation of centromere distribution by condensin II and the nuclear envelope proteins

Abstract

The arrangement of centromeres within the nucleus differs among species and cell types. However, neither the mechanisms determining centromere distribution nor its biological significance are currently well understood. In this study, we demonstrate the importance of centromere distribution for the maintenance of genome integrity through the cytogenic and molecular analysis of mutants defective in centromere distribution. We propose a two-step regulatory mechanism that shapes the non-Rabl-like centromere distribution in Arabidopsis thaliana through condensin II and the linker of the nucleoskeleton and cytoskeleton (LINC) complex. Condensin II is enriched at centromeres and, in cooperation with the LINC complex, induces the scattering of centromeres around the nuclear periphery during late anaphase/telophase. Then, after entering interphase, the positions of the scattered centromeres are stabilized by nuclear lamina proteins of the CROWDED NUCLEI (CRWN) family. We also found that, despite their strong impact on centromere distribution, condensin II and CRWNs have little effect on chromatin organization involved in the control of gene expression, indicating the robustness of chromatin organization regardless of the type of centromere distribution.

Nucleomorph: A Fascinating Remnant of Endosymbiosis

“…Moreover, Hi-C analysis suggests that while nucleomorphic chromosomes form telomere-to-telomere contacts, the majority of the genes do not interact. The data also suggest that the centromeres do not interact with each other (Marinov et al 2022), unlike many other eukaryotes (Hoencamp et al 2021, Sakamoto et al 2022). Surprisingly, it was also observed that the genomes of the host-derived mitochondrion and the nucleomorph interact (Marinov et al 2022).…”