During cell division, chromosome segregation is orchestrated by the interaction of spindle microtubules with the centromere. A dramatic remodeling of interpolar microtubules into an organized central spindle between t...During cell division, chromosome segregation is orchestrated by the interaction of spindle microtubules with the centromere. A dramatic remodeling of interpolar microtubules into an organized central spindle between the separating chromatids is required for the initiation and execution ofcytokinesis. Central spindle organization requires mitotic kinesins, the chromosomal passenger protein complex, and microtubule bundling protein PRC 1. PRC 1 is phosphorylated by Cdc2 at Thr470 and Thr481 during mitosis. However, the functional relevance of PRC 1 phosphorylation at Thr470 has remained elusive. Here we show that expression of the non-phosphorylatable mutant PRC 1T470A but not the phospho-mimicking mutant PRC 1^T470E causes aberrant organization of the central spindle. Immunoprecipitation experiment indicates that both PRC 1^T470A and PRC 1^T470E mutant proteins associate with wild-type PRC 1, suggesting that phosphorylation of Thr470 does not alter PRC 1 self-association. In addition, in vitro co-sedimentation experiment showed that PRC 1 binds to microtubule independent of the phosphorylation state of Thr470. Gel-filtration experiment suggested that phosphorylation of Thr470 promotes oligomerization of PRC 1. Given the fact that prevention of the Thr470 phosphorylation inhibits PRC 1 oligomerization in vitro and causes an aberrant organization of central spindle in vivo, we propose that this phosphorylation-dependent PRC 1 oligomerization ensures that central spindle assembly occurs at the appropriate time in the cell cycle.展开更多
Dear Editor,Polycomb group(Pc G)proteins represent important roles in repressing gene expression throughout development.The Polycomb repressive complexes(PRCs)have been subdivided into two central protein complexes,PR...Dear Editor,Polycomb group(Pc G)proteins represent important roles in repressing gene expression throughout development.The Polycomb repressive complexes(PRCs)have been subdivided into two central protein complexes,PRC1 and PRC2.PRC1 catalyzes H2AK119ub and PRC2catalyzes H3K27me1/2/3(Fursova et al.,2019).PRC1 is further categorized as CBX-containing canonical PRC1(c PRC1)and RYBP/YAF2-containing variant PRC1(v PRC1)(Blackledge and Klose,2021).展开更多
Error-free cell division depends on the accurate assembly of the spindle midzone from dynamic spindle microtubules to ensure chromatid segregation during metaphase-anaphase transition.However,the mechanism underlying ...Error-free cell division depends on the accurate assembly of the spindle midzone from dynamic spindle microtubules to ensure chromatid segregation during metaphase-anaphase transition.However,the mechanism underlying the key transition from the mitotic spindle to central spindle before anaphase onset remains elusive.Given the prevalence of chromosome instability phenotype in gastric tumorigenesis,we developed a strategy to model context-dependent cell division using a combination of light sheet microscope and 3D gastric organoids.Light sheet microscopic image analyses of 3D organoids showed that CENP-E inhibited cells undergoing aberrant metaphase-anaphase transition and exhibiting chromosome segregation errors during mitosis.Highresolution real-time imaging analyses of 2D cell culture revealed that CENP-E inhibited cells undergoing central spindle splitting and chromosome instability phenotype.Using biotinylated syntelin as an affinity matrix,we found that CENP-E forms a complex with PRC1 in mitotic cells.Chemical inhibition of CENP-E in metaphase by syntelin prevented accurate central spindle assembly by perturbing temporal assembly of PRC1 to the midzone.Thus,CENP-E-mediated PRC1 assembly to the central spindle constitutes a temporal switch to organize dynamic kinetochore microtubules into stable midzone arrays.These findings reveal a previously uncharacterized role of CENP-E in temporal control of central spindle assembly.Since CENP-E is absent from yeast,we reasoned that metazoans evolved an elaborate central spindle organization machinery to ensure accurate sister chromatid segregation during anaphase and cytokinesis.展开更多
Polycomb group（PcG） proteins are crucial epigenetic regulators conferring transcriptional memory to cell lineages.They assemble into multi-protein complexes,e.g.,Polycomb Repressive Complex 1 and 2（PRC1,PRC2）,whic...Polycomb group（PcG） proteins are crucial epigenetic regulators conferring transcriptional memory to cell lineages.They assemble into multi-protein complexes,e.g.,Polycomb Repressive Complex 1 and 2（PRC1,PRC2）,which are thought to act in a sequential manner to stably maintain gene repression.PRC2 induces histone H3 lysine 27（H3K27） trimethylation（H3K27me3）,which is subsequently read by PRCl that further catalyzes H2A monoubiquitination（H2Aub1）,creating a transcriptional silent chromatin conformation.PRC2 components are conserved in plants and have been extensively characterized in Arabidopsis.In contrast,PRCl composition and function are more diverged between animals and plants.Only more recently,PRC1 existence in plants has been documented.Here we review the aspects of plant specific and conserved PRC1 and highlight critical roles of PRC1 components in seed embryonic trait determinacy,shoot stem cell fate determinacy,and flower development in Arabidopsis.展开更多
Epigenetic regulation on gene expression is key to the decision and maintenance of cell fates during development.One of the oldest and the most explored epigenetic machinery involves the Polycomb group(PcG)proteins,wh...Epigenetic regulation on gene expression is key to the decision and maintenance of cell fates during development.One of the oldest and the most explored epigenetic machinery involves the Polycomb group(PcG)proteins,which regulate a plethora of critical biological processes,including chromatin organization,X chromosome inactivation,proliferation and differentiation,and tumorigenesis.The functions of PcG proteins are further diversified by the highly sophisticated multi-subunit complex assembly like LEGOs[1].Biochemically,PcG proteins assemble into two major complexes with unique chromatin-modifying activities:Polycomb repressive complex(PRC)1 and PRC2.PRC1 contains a core involving E3 ubiquitin ligases RING1A and RING1B,and catalyzes monoubiquitination on lysine 119 of histone H2A(H2AK119ub1),whereas PRC2 catalyzes mono-,di-,and tri-methylation on lysine 27 of histone H3(H3K27me1/2/3).Although PRC1 and PRC2 cooperate intimately in mediating transcriptional silencing,emerging evidence suggests independent roles at a subset of PcG targets.Recently,Zhu et al.[2]revealed distinct requirements for H2AK119ub1 and H3K27me3 to repress the expression of canonical PcG targets and DNA methylation-independent non-canonical imprinting genes,respectively,during early embryonic development.展开更多
基金National Natural Science Foundation of China （39925018, 90508002 , 30121001） Chinese Academy of Science （KSCX 1-R65 and RSCX2-H10）+2 种基金 National Basic Research Program of China （973 project, 2002CB713700） American Cancer Society （RPG-99-173-01） a Gcc Breast Cancer Research award and National Institutes of Health grants DK56292 and CA89019 to XY （a GCC Eminent Scholar） and NS36194 （JW）.
文摘During cell division, chromosome segregation is orchestrated by the interaction of spindle microtubules with the centromere. A dramatic remodeling of interpolar microtubules into an organized central spindle between the separating chromatids is required for the initiation and execution ofcytokinesis. Central spindle organization requires mitotic kinesins, the chromosomal passenger protein complex, and microtubule bundling protein PRC 1. PRC 1 is phosphorylated by Cdc2 at Thr470 and Thr481 during mitosis. However, the functional relevance of PRC 1 phosphorylation at Thr470 has remained elusive. Here we show that expression of the non-phosphorylatable mutant PRC 1T470A but not the phospho-mimicking mutant PRC 1^T470E causes aberrant organization of the central spindle. Immunoprecipitation experiment indicates that both PRC 1^T470A and PRC 1^T470E mutant proteins associate with wild-type PRC 1, suggesting that phosphorylation of Thr470 does not alter PRC 1 self-association. In addition, in vitro co-sedimentation experiment showed that PRC 1 binds to microtubule independent of the phosphorylation state of Thr470. Gel-filtration experiment suggested that phosphorylation of Thr470 promotes oligomerization of PRC 1. Given the fact that prevention of the Thr470 phosphorylation inhibits PRC 1 oligomerization in vitro and causes an aberrant organization of central spindle in vivo, we propose that this phosphorylation-dependent PRC 1 oligomerization ensures that central spindle assembly occurs at the appropriate time in the cell cycle.
基金supported by the National Natural Science Foundation of China(31925009,U21A20195)the National Key Research and Development Program of China(2021YFA1100300)。
文摘Dear Editor,Polycomb group(Pc G)proteins represent important roles in repressing gene expression throughout development.The Polycomb repressive complexes(PRCs)have been subdivided into two central protein complexes,PRC1 and PRC2.PRC1 catalyzes H2AK119ub and PRC2catalyzes H3K27me1/2/3(Fursova et al.,2019).PRC1 is further categorized as CBX-containing canonical PRC1(c PRC1)and RYBP/YAF2-containing variant PRC1(v PRC1)(Blackledge and Klose,2021).
基金This work was supported in part by the National NaturalScience Foundation of China(31430054,31320103904,31621002,31671405,31601097,91854203,91753000,and91853115)'Strategic Priority Research Program'of the ChineseAcademy of Sciences(XDB19000000)+2 种基金the National Key Researchand Development Program of China(2017YFA0503600 and2016YFA-0100500)MOE Innovative Team project(IRT_17R102)and the US National Institutes of Health(CA164133,DK56292,and DK115812).
文摘Error-free cell division depends on the accurate assembly of the spindle midzone from dynamic spindle microtubules to ensure chromatid segregation during metaphase-anaphase transition.However,the mechanism underlying the key transition from the mitotic spindle to central spindle before anaphase onset remains elusive.Given the prevalence of chromosome instability phenotype in gastric tumorigenesis,we developed a strategy to model context-dependent cell division using a combination of light sheet microscope and 3D gastric organoids.Light sheet microscopic image analyses of 3D organoids showed that CENP-E inhibited cells undergoing aberrant metaphase-anaphase transition and exhibiting chromosome segregation errors during mitosis.Highresolution real-time imaging analyses of 2D cell culture revealed that CENP-E inhibited cells undergoing central spindle splitting and chromosome instability phenotype.Using biotinylated syntelin as an affinity matrix,we found that CENP-E forms a complex with PRC1 in mitotic cells.Chemical inhibition of CENP-E in metaphase by syntelin prevented accurate central spindle assembly by perturbing temporal assembly of PRC1 to the midzone.Thus,CENP-E-mediated PRC1 assembly to the central spindle constitutes a temporal switch to organize dynamic kinetochore microtubules into stable midzone arrays.These findings reveal a previously uncharacterized role of CENP-E in temporal control of central spindle assembly.Since CENP-E is absent from yeast,we reasoned that metazoans evolved an elaborate central spindle organization machinery to ensure accurate sister chromatid segregation during anaphase and cytokinesis.
基金supported by the French Centre National de la Recherche Scientifique(CNRS)the French Agence Nationale de la Recherche(ANR-08-BLAN- 0200-CSD7)
文摘Polycomb group（PcG） proteins are crucial epigenetic regulators conferring transcriptional memory to cell lineages.They assemble into multi-protein complexes,e.g.,Polycomb Repressive Complex 1 and 2（PRC1,PRC2）,which are thought to act in a sequential manner to stably maintain gene repression.PRC2 induces histone H3 lysine 27（H3K27） trimethylation（H3K27me3）,which is subsequently read by PRCl that further catalyzes H2A monoubiquitination（H2Aub1）,creating a transcriptional silent chromatin conformation.PRC2 components are conserved in plants and have been extensively characterized in Arabidopsis.In contrast,PRCl composition and function are more diverged between animals and plants.Only more recently,PRC1 existence in plants has been documented.Here we review the aspects of plant specific and conserved PRC1 and highlight critical roles of PRC1 components in seed embryonic trait determinacy,shoot stem cell fate determinacy,and flower development in Arabidopsis.
基金supported by the Chinese Ministry of Science and Technology(2019YFA0801401)the Chinese Academy of Sciences(QYZDY-SSW-SMC031)the Youth Innovation Promotion Association(2020097)of the Chinese Academy of Sciences。
文摘Epigenetic regulation on gene expression is key to the decision and maintenance of cell fates during development.One of the oldest and the most explored epigenetic machinery involves the Polycomb group(PcG)proteins,which regulate a plethora of critical biological processes,including chromatin organization,X chromosome inactivation,proliferation and differentiation,and tumorigenesis.The functions of PcG proteins are further diversified by the highly sophisticated multi-subunit complex assembly like LEGOs[1].Biochemically,PcG proteins assemble into two major complexes with unique chromatin-modifying activities:Polycomb repressive complex(PRC)1 and PRC2.PRC1 contains a core involving E3 ubiquitin ligases RING1A and RING1B,and catalyzes monoubiquitination on lysine 119 of histone H2A(H2AK119ub1),whereas PRC2 catalyzes mono-,di-,and tri-methylation on lysine 27 of histone H3(H3K27me1/2/3).Although PRC1 and PRC2 cooperate intimately in mediating transcriptional silencing,emerging evidence suggests independent roles at a subset of PcG targets.Recently,Zhu et al.[2]revealed distinct requirements for H2AK119ub1 and H3K27me3 to repress the expression of canonical PcG targets and DNA methylation-independent non-canonical imprinting genes,respectively,during early embryonic development.
