Stable transmission of genetic information during cell division requires faithful mitotic spindle assembly and chromosome segregation. The Ran GTPase plays a key role in mitotic spindle assembly. However, how the gene...Stable transmission of genetic information during cell division requires faithful mitotic spindle assembly and chromosome segregation. The Ran GTPase plays a key role in mitotic spindle assembly. However, how the generation of a chemical gradient of Ran-GTP at the spindle is coupled to mitotic post-translational modifications has never been characterized. Here, we solved the complex structure of Ran with the nucleotide release factor Mogl and delineated a novel mitosis-specific acetylation-regulated Ran-Mogl interaction dur- ing chromosome segregation. Our structure-guided functional analyses revealed that Mogl compotes with RCCl for Ran binding in a GTP/GDP-dependent manner. Biochemical characterization demonstrated that Mogl-bound Ran prevents RCCl binding and subse- quent GTP loading. Surprisingly, Ran is a bono fide substrate of TIP60, and the acetylation of Lys134 by TIP60 liberates Mogl from Ran binding during mitosis. Importantly, this acetylation-elicited switch of Ran binding to RCC1 promotes high level of Ran-GTP, which is essential for chromosome alignment. These results establish a previously uncharacterized regulatory mechanism in which TIP60 pro- vides a homeostatic control of Ran-GTP level by tuning Ran effector binding for chromosome segregation in mitosis.展开更多
Mammalian AlkB homologue 2(ALKBH2)is the primary housekeeping DNA demethylase,effectively repairing endogenously formed methylated lesions in double-stranded DNA.Our previous studies demonstrated that a hydrophobicβ-...Mammalian AlkB homologue 2(ALKBH2)is the primary housekeeping DNA demethylase,effectively repairing endogenously formed methylated lesions in double-stranded DNA.Our previous studies demonstrated that a hydrophobicβ-hairpin motif of ALKBH2 could play crucial roles in base-pair stability interrogation and damaged base flipping.Using chemical cross-linking strategy,we obtained two crystal structures of human ALKBH2 mutant bound to duplex DNA.The structural analysis suggests that theβ-hairpin motif is flexible in conformation and is likely to slide along the DNA duplex in local regions to search for damaged base.This study provides a new mechanistic insight into DNA damage detection by ALKBH2.展开更多
文摘Stable transmission of genetic information during cell division requires faithful mitotic spindle assembly and chromosome segregation. The Ran GTPase plays a key role in mitotic spindle assembly. However, how the generation of a chemical gradient of Ran-GTP at the spindle is coupled to mitotic post-translational modifications has never been characterized. Here, we solved the complex structure of Ran with the nucleotide release factor Mogl and delineated a novel mitosis-specific acetylation-regulated Ran-Mogl interaction dur- ing chromosome segregation. Our structure-guided functional analyses revealed that Mogl compotes with RCCl for Ran binding in a GTP/GDP-dependent manner. Biochemical characterization demonstrated that Mogl-bound Ran prevents RCCl binding and subse- quent GTP loading. Surprisingly, Ran is a bono fide substrate of TIP60, and the acetylation of Lys134 by TIP60 liberates Mogl from Ran binding during mitosis. Importantly, this acetylation-elicited switch of Ran binding to RCC1 promotes high level of Ran-GTP, which is essential for chromosome alignment. These results establish a previously uncharacterized regulatory mechanism in which TIP60 pro- vides a homeostatic control of Ran-GTP level by tuning Ran effector binding for chromosome segregation in mitosis.
基金financially supported by the Hundred Talents Program of the Chinese Academy of Sciences,Key Project of Chinese National Programs for Fundamental Research and Development(2009CB918502)
文摘Mammalian AlkB homologue 2(ALKBH2)is the primary housekeeping DNA demethylase,effectively repairing endogenously formed methylated lesions in double-stranded DNA.Our previous studies demonstrated that a hydrophobicβ-hairpin motif of ALKBH2 could play crucial roles in base-pair stability interrogation and damaged base flipping.Using chemical cross-linking strategy,we obtained two crystal structures of human ALKBH2 mutant bound to duplex DNA.The structural analysis suggests that theβ-hairpin motif is flexible in conformation and is likely to slide along the DNA duplex in local regions to search for damaged base.This study provides a new mechanistic insight into DNA damage detection by ALKBH2.
