The tumor suppressor p53 locates at the key point of cell growth or apoptosis balance, and the expression level of p53 is tightly controlled by ubiquitin ligases including MDM2. Upon DNA damage stresses, p53 was accum...The tumor suppressor p53 locates at the key point of cell growth or apoptosis balance, and the expression level of p53 is tightly controlled by ubiquitin ligases including MDM2. Upon DNA damage stresses, p53 was accumulated and activated, leading to cell cycle arrest or apoptosis. We previously showed that Smad ubiquitylation regulatory factor 1/2 (Smurf1/2) promotes p53 degradation by interacting with and stabilizing MDM2, and consequently enhancing MDM2-mediated ubiquitylation of p53. However, it is unclear how the Smurf1-MDM2 interaction is regulated in response to DNA damage stress. Here, we show that in response to etoposide treatment Smurf1 dissociates from MDM2, resulting in MDM2 destabilization and p53 accumulation. The negative regulation of Smurf1 on apoptosis is released. Notably, this dissociation is a slow process rather than a rapid response, implicating high expression of Smurf1 might confer the resistance against p53 activation. Consistent with this notion, we observed that Smurf1/2 ligases are highly expressed in colon cancer, esophageal squamous cell carcinoma and pancreatic cancer tissues, suggesting the oncogenic tendency of Smurf1/2.展开更多
The post translational modifications of histone variants are playing an important role in the structure of chromatin, the regulation of gene activities and the diagnosis of diseases, and conducting in-depth researches...The post translational modifications of histone variants are playing an important role in the structure of chromatin, the regulation of gene activities and the diagnosis of diseases, and conducting in-depth researches and discovering new sites depend on new and rational analytical methods to some extent. In this work, the combinatorial method of high resolution LTQ-Orbitrap mass spectrometry and multiple enzymes was employed to identify the post translational modifications （PTMs） of histone H4 of human liver cells. The novel methylation site, argnine 67 （R 67）, was observed besides some sites reported previously such as lysine 31 （K 31）, lysine 44 （K 44）, argnine 55 （R 55） and lysine 59 （K 59） in the global domain. Meanwhile, various combinations of acetylation of lysine 5 （K 5）, lysine 8 （K 8）, lysine 12 （K 12）, lysine 16 （K 16） and methylation of lysine 20 （K 20） in the NH2-terminal tails were also identified after the LC-MS/MS analysis of trypsin, Arg-C, Glu-C and chymotrypsin digests.展开更多
基金supported by the National Natural Science Foundation of China (31100554, 30800177)the National Basic Research Program of China (2007CB914601, 2011CB910802)
文摘The tumor suppressor p53 locates at the key point of cell growth or apoptosis balance, and the expression level of p53 is tightly controlled by ubiquitin ligases including MDM2. Upon DNA damage stresses, p53 was accumulated and activated, leading to cell cycle arrest or apoptosis. We previously showed that Smad ubiquitylation regulatory factor 1/2 (Smurf1/2) promotes p53 degradation by interacting with and stabilizing MDM2, and consequently enhancing MDM2-mediated ubiquitylation of p53. However, it is unclear how the Smurf1-MDM2 interaction is regulated in response to DNA damage stress. Here, we show that in response to etoposide treatment Smurf1 dissociates from MDM2, resulting in MDM2 destabilization and p53 accumulation. The negative regulation of Smurf1 on apoptosis is released. Notably, this dissociation is a slow process rather than a rapid response, implicating high expression of Smurf1 might confer the resistance against p53 activation. Consistent with this notion, we observed that Smurf1/2 ligases are highly expressed in colon cancer, esophageal squamous cell carcinoma and pancreatic cancer tissues, suggesting the oncogenic tendency of Smurf1/2.
基金Project supported by the National Science and Technology Key Project （No. 2009CB825607）, National Natural Science Foundation of China （Nos. 20875016, 31070732）, Ministry of Education of China （20080246011）, Shanghai Projects （Shuguang Eastern Scholar and B 109）.
文摘The post translational modifications of histone variants are playing an important role in the structure of chromatin, the regulation of gene activities and the diagnosis of diseases, and conducting in-depth researches and discovering new sites depend on new and rational analytical methods to some extent. In this work, the combinatorial method of high resolution LTQ-Orbitrap mass spectrometry and multiple enzymes was employed to identify the post translational modifications （PTMs） of histone H4 of human liver cells. The novel methylation site, argnine 67 （R 67）, was observed besides some sites reported previously such as lysine 31 （K 31）, lysine 44 （K 44）, argnine 55 （R 55） and lysine 59 （K 59） in the global domain. Meanwhile, various combinations of acetylation of lysine 5 （K 5）, lysine 8 （K 8）, lysine 12 （K 12）, lysine 16 （K 16） and methylation of lysine 20 （K 20） in the NH2-terminal tails were also identified after the LC-MS/MS analysis of trypsin, Arg-C, Glu-C and chymotrypsin digests.
