Kinetochore-independent mechanisms of sister chromosome separation.
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 sep...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Public Library of Science (PLoS)
2021-01-01
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| Series: | PLoS Genetics |
| Online Access: | https://journals.plos.org/plosgenetics/article/file?id=10.1371/journal.pgen.1009304&type=printable |
| _version_ | 1826574431172952064 |
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| author | Hannah Vicars Travis Karg Brandt Warecki Ian Bast William Sullivan |
| author_facet | Hannah Vicars Travis Karg Brandt Warecki Ian Bast William Sullivan |
| author_sort | Hannah Vicars |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-12-21T05:53:23Z |
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| id | doaj.art-f6901eb7204a492c8072e17c2fe1b618 |
| institution | Directory Open Access Journal |
| issn | 1553-7390 1553-7404 |
| language | English |
| last_indexed | 2025-03-14T12:58:41Z |
| publishDate | 2021-01-01 |
| publisher | Public Library of Science (PLoS) |
| record_format | Article |
| series | PLoS Genetics |
| spelling | doaj.art-f6901eb7204a492c8072e17c2fe1b6182025-03-02T05:31:39ZengPublic Library of Science (PLoS)PLoS Genetics1553-73901553-74042021-01-01171e100930410.1371/journal.pgen.1009304Kinetochore-independent mechanisms of sister chromosome separation.Hannah VicarsTravis KargBrandt WareckiIan BastWilliam SullivanAlthough 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.https://journals.plos.org/plosgenetics/article/file?id=10.1371/journal.pgen.1009304&type=printable |
| spellingShingle | Hannah Vicars Travis Karg Brandt Warecki Ian Bast William Sullivan Kinetochore-independent mechanisms of sister chromosome separation. PLoS Genetics |
| title | Kinetochore-independent mechanisms of sister chromosome separation. |
| title_full | Kinetochore-independent mechanisms of sister chromosome separation. |
| title_fullStr | Kinetochore-independent mechanisms of sister chromosome separation. |
| title_full_unstemmed | Kinetochore-independent mechanisms of sister chromosome separation. |
| title_short | Kinetochore-independent mechanisms of sister chromosome separation. |
| title_sort | kinetochore independent mechanisms of sister chromosome separation |
| url | https://journals.plos.org/plosgenetics/article/file?id=10.1371/journal.pgen.1009304&type=printable |
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