ESCRT-III–mediated membrane fusion drives chromosome fragments through nuclear envelope channels

Warecki, Brandt; Ling, Xi; Bast, Ian; Sullivan, William M.

doi:10.1083/jcb.201905091

Cited by 23 publications

(15 citation statements)

References 84 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This indicates that the knockdowns in the genes identified in this study specifically disrupt acentric sister separation as the subsequent transmission occurs normally to allow incorporation of the acentric into the daughter nuclei. This interpretation is in accord with a model that acentrics experience different forces at different stages of their separation, transmission, and incorporation into daughter nuclei [64].…”

Section: Discussionsupporting

confidence: 87%

Kinetochore-independent mechanisms of sister chromosome separation

Vicars

Karg

Warecki

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

Although centromeres play a key role in sister chromatid separation and segregation, mitotic transmission of chromosome fragments lacking a centromere (acentrics) can be successful. In Drosophila neuroblasts, acentric chromosomes undergo delayed, but successful transmission revealing the existence of kinetochore-independent mechanisms driving transmission. In spite of delayed sister chromatid separation, bulk cohesin removal from the acentric is not delayed, suggesting factors other than cohesin are responsible for the delay. In contrast to intact kinetochore-bearing chromosomes, we discovered that acentrics align parallel as well as perpendicular to the mitotic spindle. In addition, sister acentrics undergo unconventional patterns of separation. For example, rather than the simultaneous separation of sisters, acentrics oriented parallel to the spindle often slide past one another toward opposing poles. To identify the mechanisms driving acentric separation, we screened 117 RNAi gene knockdowns for synthetic lethality with acentric chromosome fragments. In addition to well-established DNA repair and checkpoint mutants, this candidate screen identified synthetic lethality with X-chromosome-derived acentric fragments in knockdowns of Greatwall (cell cycle kinase), EB1 (plus-end tracking protein), and Map205 (microtubule-stabilizing protein). Additional image-based screening revealed that reductions in Topoisomerase II levels disrupted sister acentric separation. Intriguingly, live imaging revealed that knockdowns of EB1, Map205, and Greatwall preferentially disrupted the sliding mode of sister acentric separation. In spite of these failures in acentric separation, acentrics incorporated into daughter nuclei and there was no increase in micronuclei formation. Based on our analysis of EB1 localization and knockdown phenotypes, we propose that in the absence of a kinetochore, microtubule plus-end dynamics provide the force to resolve DNA catenations required for sister separation.AUTHOR SUMMARYCentromeres, the site on the chromosomes to which microtubules attach driving the separation and segregation of replicated sister chromosomes, have been viewed as essential for proper cell division and accurate transmission of chromosomes into daughter cells. However previous studies demonstrated that sister chromosomes lacking a centromere (acentrics) often undergo separation, segregation and transmission. Here we demonstrate that sister acentrics are held together through DNA intertwining. During anaphase, acentric sister separation is achieved through Topoisomerase activity, an enzyme that resolves these DNA linkages, as well as forces generated on the acentrics by the growing ends of highly dynamic microtubule polymers. We found acentric sister chromatids display unique patterns of separation using mechanisms independent of the centromere. Additionally, we identified the specific microtubule-associated proteins required for the successful mitotic transmission of acentric chromosomes to daughter cells. These studies reveal unsuspected, distinct forces that likely act on all chromosomes during mitosis independent of centromere-microtubule attachments.

show abstract

Section: Discussionsupporting

confidence: 87%

Kinetochore-independent mechanisms of sister chromosome separation

Vicars

Karg

Warecki

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…It should be noted that although these mutants resulted in a high frequency of failed acentric sister separation, we did not observe an equivalent increase in micronuclei. In contrast, mutants that disrupted acentric poleward transport or the final stages of incorporation into daughter nuclei resulted in an accompanying increase in micronuclei [ 66 – 68 ]. This indicates that the knockdowns in the genes identified in this study specifically disrupt acentric sister separation as the subsequent transmission occurs normally to allow incorporation of the acentric into the daughter nuclei.…”

Section: Discussionmentioning

confidence: 99%

Kinetochore-independent mechanisms of sister chromosome separation

et al. 2021

Self Cite

View full text Add to dashboard Cite

Although kinetochores normally play a key role in sister chromatid separation and segregation, chromosome fragments lacking kinetochores (acentrics) can in some cases separate and segregate successfully. In Drosophila neuroblasts, acentric chromosomes undergo delayed, but otherwise normal sister separation, revealing the existence of kinetochore- independent mechanisms driving sister chromosome separation. Bulk cohesin removal from the acentric is not delayed, suggesting factors other than cohesin are responsible for the delay in acentric sister separation. In contrast to intact kinetochore-bearing chromosomes, we discovered that acentrics align parallel as well as perpendicular to the mitotic spindle. In addition, sister acentrics undergo unconventional patterns of separation. For example, rather than the simultaneous separation of sisters, acentrics oriented parallel to the spindle often slide past one another toward opposing poles. To identify the mechanisms driving acentric separation, we screened 117 RNAi gene knockdowns for synthetic lethality with acentric chromosome fragments. In addition to well-established DNA repair and checkpoint mutants, this candidate screen identified synthetic lethality with X-chromosome-derived acentric fragments in knockdowns of Greatwall (cell cycle kinase), EB1 (microtubule plus-end tracking protein), and Map205 (microtubule-stabilizing protein). Additional image-based screening revealed that reductions in Topoisomerase II levels disrupted sister acentric separation. Intriguingly, live imaging revealed that knockdowns of EB1, Map205, and Greatwall preferentially disrupted the sliding mode of sister acentric separation. Based on our analysis of EB1 localization and knockdown phenotypes, we propose that in the absence of a kinetochore, microtubule plus-end dynamics provide the force to resolve DNA catenations required for sister separation.

show abstract

“…This would leave an open channel to the main nucleus through which the acentric can pass, suggesting that membrane fusion is not necessarily required for reintegration of these tethered acentrics. The specific role of ESCRT and other membrane remodeling proteins in this process merits additional study [126]. Because ESCRT normally seals the spindle-proximal core membranes [17], we speculate that ESCRT on these acentrics might reflect ESCRT's normal function at the core domain: sealing the assembling NE and removing the acentrics-associated microtubule bundles [127], rather than opening up a closed membrane to allow acentric entry.…”

Section: Transient Ne Subdomain Formation During Normal Ne Reassemblymentioning

confidence: 99%

“…A recent study from Warecki et al has raised the possibility of an ESCRT-III-mediated membrane fusion event associated the reintegration of nuclease-generated acentric chromosome fragments Drosophila neuroblasts [126]. However, in this case, the acentric is connected to the main chromosome mass by a chromatin bridge ('DNA tether').…”

Section: Transient Ne Subdomain Formation During Normal Ne Reassemblymentioning

confidence: 99%

The coordination of nuclear envelope assembly and chromosome segregation in metazoans

Liu

Pellman

2020

Nucleus

View full text Add to dashboard Cite

The nuclear envelope (NE) is composed of two lipid bilayer membranes that enclose the eukaryotic genome. In interphase, the NE is perforated by thousands of nuclear pore complexes (NPCs), which allow transport in and out of the nucleus. During mitosis in metazoans, the NE is broken down and then reassembled in a manner that enables proper chromosome segregation and the formation of a single nucleus in each daughter cell. Defects in coordinating NE reformation and chromosome segregation can cause aberrant nuclear architecture. This includes the formation of micronuclei, which can trigger a catastrophic mutational process commonly observed in cancers called chromothripsis. Here, we discuss the current understanding of the coordination of NE reformation with chromosome segregation during mitotic exit in metazoans. We review differing models in the field and highlight recent work suggesting that normal NE reformation and chromosome segregation are physically linked through the timing of mitotic spindle disassembly.

show abstract

ESCRT-III–mediated membrane fusion drives chromosome fragments through nuclear envelope channels

Cited by 23 publications

References 84 publications

Kinetochore-independent mechanisms of sister chromosome separation

Kinetochore-independent mechanisms of sister chromosome separation

Kinetochore-independent mechanisms of sister chromosome separation

The coordination of nuclear envelope assembly and chromosome segregation in metazoans

Contact Info

Product

Resources

About