分类： 生物学 >> 生物物理学 >> 细胞生物学 提交时间： 2016-05-12
Yu, Zhouliang
Zhou, Xiang
Wang, Wenjing
Deng, Wenqiang
Fang, Junnan
Hu, Hao
Wang, Zichen
Cui, Lei
Shen, Jing
Ou, Guangshuo
Yang, Na
Chen, Ping
Xu, Rui-Ming
Li, Guohong
Yu, Zhouliang
Deng, Wenqiang
Fang, Junnan
Hu, Hao
Peng, Shengyi
Li, Shangze
摘要： The H3 histone variant CENP-A is an epigenetic marker critical for the centromere identity and function. However, the precise regulation of the spatiotemporal deposition and propagation of CENP-A at centromeres during the cell cycle is still poorly understood. Here, we show that CENP-A is phosphorylated at Ser68 during early mitosis by Cdk1. Our results demonstrate that phosphorylation of Ser68 eliminates the binding of CENP-A to the assembly factor HJURP, thus preventing the premature loading of CENP-A to the centromere prior to mitotic exit. Because Cdk1 activity is at its minimum at the mitotic exit, the ratio of Cdk1/PP1 alpha activity changes in favor of Ser68 dephosphorylation, thus making CENP-A available for centromeric deposition by HJURP. Thus, we reveal that dynamic phosphorylation of CENP-A Ser68 orchestrates the spatiotemporal assembly of newly synthesized CENP-A at active centromeres during the cell cycle.
分类： 生物学 >> 生物物理学 >> 细胞生物学 提交时间： 2016-05-12
Fang, Junnan
Liu, Yuting
Wei, Yun
Deng, Wenqiang
Yu, Zhouliang
Huang, Li
Teng, Yan
Yao, Ting
You, Qinglong
Ruan, Haihe
Chen, Ping
Xu, Rui-Ming
Li, Guohong
Fang, Junnan
Liu, Yuting
Deng, Wenqiang
Yu, Zhouliang
You, Qinglong
摘要： Specific recognition of centromere-specific histone variant CENP-A-containing chromatin by CENP-N is an essential process in the assembly of the kinetochore complex at centromeres prior to mammalian cell division. However, the mechanisms of CENP-N recruitment to centromeres/kinetochores remain unknown. Here, we show that a CENP-A-specific RG loop (Arg80/Gly81) plays an essential and dual regulatory role in this process. The RG loop assists the formation of a compact "ladder-like" structure of CENP-A chromatin, concealing the loop and thus impairing its role in recruiting CENP-N. Upon G1/S-phase transition, however, centromeric chromatin switches from the compact to an open state, enabling the now exposed RG loop to recruit CENP-N prior to cell division. Our results provide the first insights into the mechanisms by which the recruitment of CENP-N is regulated by the structural transitions between compaction and relaxation of centromeric chromatin during the cell cycle.
分类： 生物学 >> 生物物理学 >> 细胞生物学 提交时间： 2016-05-12
Cao, Duanfang
Wang, Mingzhu
Yang, Na
Xu, Rui-Ming
Cao, Duanfang
Xu, Rui-Ming
Qiu, Xiayang
Liu, Dongxiang
Jiang, Hualiang
摘要： Sirtuins with an extended N-terminal domain (NTD), represented by yeast Sir2 and human SIRT1, harbor intrinsic mechanisms for regulation of their NAD-dependent deacetylase activities. Elucidation of the regulatory mechanisms is crucial for understanding the biological functions of sirtuins and development of potential therapeutics. In particular, SIRT1 has emerged as an attractive therapeutic target, and the search for SIRT1-activating compounds (STACs) has been actively pursued. However, the effectiveness of a class of reported STACs (represented by resveratrol) as direct SIRT1 activators is under debate due to the complication involving the use of fluorogenic substrates in in vitro assays. Future efforts of SIRT1-based therapeutics necessitate the dissection of the molecular mechanism of SIRT1 stimulation. We solved the structure of SIRT1 in complex with resveratrol and a 7-amino-4-methylcoumarin (AMC)-containing peptide. The structure reveals the presence of three resveratrol molecules, two of which mediate the interaction between the AMC peptide and the NTD of SIRT1. The two NTD-bound resveratrol molecules are principally responsible for promoting tighter binding between SIRT1 and the peptide and the stimulation of SIRT1 activity. The structural information provides valuable insights into regulation of SIRT1 activity and should benefit the development of authentic SIRT1 activators.
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