BRCA1 and its phosphorylation involved in caffeine-inhibitable event upstream of G2 checkpoint  

作　　者：LI Ning ZHANG Hong WANG YanLing HAO JiFang 

机构地区：[1]Institute of Modern Physics,Chinese Academy of Sciences,Lanzhou 730000,China [2]Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences,Lanzhou 730000,China [3]Key Laboratory of Heavy Ion Radiation Medicine of Gansu Province,Lanzhou 730000,China [4] Graduate University of Chinese Academy of Sciences,Beijing 100039,China

出　　处：《Science China(Physics,Mechanics & Astronomy)》2010年第7期1281-1285,共5页中国科学:物理学、力学、天文学(英文版)

基　　金：supported by the National Basic Research Program of China (Grant No. 2010CB834202);the National Natural Science Foundation of China (Grant Nos. 10835011and 10805064);the Scientific Technology Research Projects of Gansu Province (Grant Nos. 0806RJYA020 and 099RJYA015);Western Talent Program of Chinese Academy of Sciences (Grant No. 0860260XBO)

摘　　要：Caffeine,which specifically inhibits ATM/ATR kinases,efficiently abrogates the ionizing radiation(IR)-induced G2 arrest and increases the sensitivity of various tumor cells to IR.Mechanisms for the effect of caffeine remain to be elucidated.As a target of ATM/ATR kinases,BRCA1 becomes activated and phosphorylated in response to IR.Thus,in this work,we investigated the possible role of BRCA1 in the effect of caffeine on G2 checkpoint and observed how BRCA1 phosphorylation was regulated in this process.For these purposes,the BRCA1 protein level and the phosphorylation states were analyzed by Western blotting by using an antibody against BRCA1 and phospho-specific antibodies against Ser-1423 and Ser-1524 residues in cells exposed to a combination of IR and caffeine.The results showed that caffeine down-regulated IR-induced BRCA1 expression and specifically abolished BRCA1 phosphorylation of Ser-1524,which was followed by an override of G2 arrest by caffeine.In addition,the ability of BRCA1 to transactivate p21 may be required for MCF-7 but not necessary for Hela response to caffeine.These data suggest that BRCA1 may be a potential target of caffeine.BRCA1 and its phosphorylation are most likely to be involved in the caffeine-inhibitable event upstream of G2 arrest.Caffeine,which specifically inhibits ATM/ATR kinases,efficiently abrogates the ionizing radiation(IR)-induced G2 arrest and increases the sensitivity of various tumor cells to IR.Mechanisms for the effect of caffeine remain to be elucidated.As a target of ATM/ATR kinases,BRCA1 becomes activated and phosphorylated in response to IR.Thus,in this work,we investigated the possible role of BRCA1 in the effect of caffeine on G2 checkpoint and observed how BRCA1 phosphorylation was regulated in this process.For these purposes,the BRCA1 protein level and the phosphorylation states were analyzed by Western blotting by using an antibody against BRCA1 and phospho-specific antibodies against Ser-1423 and Ser-1524 residues in cells exposed to a combination of IR and caffeine.The results showed that caffeine down-regulated IR-induced BRCA1 expression and specifically abolished BRCA1 phosphorylation of Ser-1524,which was followed by an override of G2 arrest by caffeine.In addition,the ability of BRCA1 to transactivate p21 may be required for MCF-7 but not necessary for Hela response to caffeine.These data suggest that BRCA1 may be a potential target of caffeine.BRCA1 and its phosphorylation are most likely to be involved in the caffeine-inhibitable event upstream of G2 arrest.

关 键 词：BRCA1 PHOSPHORYLATION ionizing irradiation CAFFEINE G2 checkpoint 

分 类 号：Q343[生物学—遗传学]