DrosophilaCAP-D2 is required for condensin complex stability and resolution of sister chromatids

Abstract

The precise mechanism of chromosome condensation and decondensation remains a mystery, despite progress over the last 20 years aimed at identifying components essential to the mitotic compaction of the genome. In this study, we analyse the localization and role of the CAP-D2 non-SMC condensin subunit and its effect on the stability of the condensin complex. We demonstrate that a condensin complex exists in Drosophila embryos, containing CAP-D2, the anticipated SMC2 and SMC4 proteins, the CAP-H/Barren and CAP-G (non-SMC) subunits. We show that CAP-D2 is a nuclear protein throughout interphase, increasing in level during S phase, present on chromosome axes in mitosis, and still present on chromosomes as they start to decondense late in mitosis. We analysed the consequences of CAP-D2 loss after dsRNA-mediated interference, and discovered that the protein is essential for chromosome arm and centromere resolution. The loss of CAP-D2 after RNAi has additional downstream consequences on the stability of CAP-H, the localization of DNA topoisomerase II and other condensin subunits, and chromosome segregation. Finally, we discovered that even after interfering with two components important for chromosome architecture (DNA topoisomerase II and condensin), chromosomes were still able to compact, paving the way for the identification of further components or activities required for this essential process.

Escherichia coli condensin MukB stimulates topoisomerase IV activity by a direct physical interaction

“…It has been reported that the Drosophila non-SMC condensin subunit Barren (CAP-H) interacts with Topo II, stimulating its activity (66). Consistent with this report, depletion of the Condensin I non-SMC subunit CAP-D2 leads to an alteration of the spatial organization of Topo II in both Drosophila and humans, along with a change in CAP-H levels or localization (67,68). Moreover, Topo II appears to be improperly localized in mitotic chromosomes from SMC-2 or SMC-4 depleted cell extracts (for a review, see ref.…”

Chromosome Dynamics during Mitosis

“…Moreover, the condensin II-specific subunits apparently play less-important roles than the condensin I-specific subunits during the mitotic chromosome cycle in organisms, such as Drosophila (Savvidou et al 2005;Herzog et al 2013), Arabidopsis thaliana (Sakamoto et al 2011), and C. merolae (Fujiwara et al 2013). Consistent with this view, genome-wide screens for genes affecting chromosome condensation in yeasts and Drosophila have identified condensin I and topoisomerase II (Hirano et al 1986;Samejima et al 1993;Goshima et al 2007;Petrova et al 2012), implicating that no more "major" condensation factors remain to be discovered, at least in these organisms.…”

Disruption of Topoisomerase II Perturbs Pairing in Drosophila Cell Culture

“…Top2 encodes the single Drosophila type II DNA topoisomerase, which represents a class of enzymes that generate double-strand breaks (DSBs), can catenate and decatenate DNA, and are well known for their role in chromosome structure and condensation and sister chromatid segregation (reviewed by Porter and Farr 2004; also see Chang et al 2003;Coelho et al 2003;Savvidou et al 2005;Smiley et al 2007). We have found that treatment of log-phase Kc 167 cells with any one of three dsRNAs directed against Top2 function followed by FISH targeting 28B1 reduced the percentage of nuclei with a single signal from 87 6 1% to 55 6 5% (P , 0.0001; Figure 6, A and B) and lowered pairing levels from 91 to 71% (P , 0.0001; Figure 6C).…”