@article{1594b910714a44f9aa4882bfb9c33a56,
title = "Nuclear exclusion of separase prevents cohesin cleavage in interphase cells",
abstract = "During mitosis, equal transmission of the duplicated chromosomes demands a strict regulation of separase, which cleaves cohesin and triggers sister chromatid separation in anaphase. Vertebrate separase is inhibited by securin and the inhibitory phosphorylation of separase. However, knockout experiments indicate that securin is dispensable and the inhibitory phosphorylation was observed only in M phase cells. This begs the question how cohesin cleavage by separase is prevented in the absence these two mechanisms. Here we show that separase is excluded from cohesin by the nuclear envelope, which forms in telophase and disassembles in mitosis. The exclusion is achieved passively by its large physical mass and may be backed up by the CRM1-dependent nuclear export. A functional NES motif is identified in separase. We demonstrated that the nuclear envelope is sufficient to prevent active separase from cleaving nuclear cohesin. We propose that the nuclear exclusion is important to prevent cohesin cleavage during interphase in the absence of securin and the phosphorylation inhibition.",
keywords = "Cell cycle, Chromatid separation, Mitosis, Nuclear export, Separate",
author = "Yuxiao Sun and Hong Yu and Hui Zou",
note = "Funding Information: Separase, chromatid separation, nuclear export, mitosis, cell cycle Immediately after DNA replication, sister chromatids are physically attached to each other by the four-subunit cohesin complex (kleisin SCC1/MCD1/RAD21, SCC3, SMC1 and SMC3). Although co.h eDsioOn iNs eOstablished in S phase, the binding of the cohesin We thank C. Lengauer for generously complex to chromosomes occurs earlier and this pre-S-phase association is believed to be providing the securin deletion HCT116 cells. the first step of a multi-phase mechanism that leads to the establishment of sister-chro-We are also grateful to D. Pellman for the stable matid cohesion.1,2 At the metaphase-anaphase transition, cohesion is dissolved following separase-V5 cell line. H.Z. is the Kenneth the proteolytic cleavage of cohesin at the kleisin subunit by a cysteine endopeptidase called G. and Elaine A. Langone Scholar supported separase,3 which triggers the final separation of sister-chromatids. by the Damon Runyon Cancer Foundation The cleavage of cohesin by separase is both sufficient and necessary for chromatid (DRS-#35-03). The work is also supported by separation.4-7 To ensure timely separation of chromatids, the activity of separase is a Research Scholar Grant from the American regulated by redundant mechanisms: separase is inhibited by securin5,8-11 and, in Cancer Society (RSG-04-171-01-CCG) and vertebrates, by phosphorylation on separase.12-14 In addition, more regulatory mecha-a research grant from the Welch Foundation nisms are expected based on several observations. First, in telophase and early G1, both (I-1594) to H.Z. aforementioned inhibitory mechanisms are shutdown by the anaphase-promoting complex or cyclosome (APC/C). Despite the activity of separase during these stages of the cell cycle, the vertebrate cohesin complex colocalizes with chromosomes.15 Second, human cells and mice deleted of both alleles of securin are alive and largely normal.16-19Third, despite the sensitivity to microtubule poisons, mouse ES cells, containing homozygous deletion of securin and heterozygous of a phosphorylation-inhibition resistant separase,20 is largely normal. Taken together, these results suggest that separase is regulated by additional mechanisms. In this report, we demonstrated that vertebrate separase is excluded from the nucleus in interphase cells. The exclusion is ensured by both its large size and the nuclear export mechanism. We propose that nuclear exclusion is yet another mechanism that prevents the",
year = "2006",
month = nov,
day = "1",
doi = "10.4161/cc.5.21.3407",
language = "English (US)",
volume = "5",
pages = "2537--2542",
journal = "Cell Cycle",
issn = "1538-4101",
publisher = "Landes Bioscience",
number = "21",
}