title: BRAT1 deficiency causes increased glucose metabolism and mitochondrial malfunction.
abstract: BACKGROUND
  BRAT1 (BRCA1-associated ATM activator 1) interacts with both BRCA1, ATM and DNA-PKcs, and has been implicated in DNA damage responses. However, based on our previous results, it has been shown that BRAT1 may be involved in cell growth and apoptosis, besides DNA damage responses, implying that there are undiscovered functions for BRAT1.
  
  
  METHODS
  Using RNA interference against human BRAT1, we generated stable BRAT1 knockdown cancer cell lines of U2OS, Hela, and MDA-MA-231. We tested cell growth properties and in vitro/in vivo tumorigenic potentials of BRAT1 knockdown cells compared to control cells. To test if loss of BRAT1 induces metabolic abnormalities, we examined the rate of glycolysis, ATP production, and PDH activity in both BRAT1 knockdown and control cells. The role of BRAT1 in growth signaling was determined by the activation of Akt/Erk, and SC79, Akt activator was used for validation.
  
  
  RESULTS
  By taking advantage of BRAT1 knockdown cancer cell lines, we found that loss of BRAT1 expression significantly decreases cell proliferation and tumorigenecity both in vitro and in vivo. Cell migration was also remarkably lowered when BRAT1 was depleted. Interestingly, glucose uptake and production of mitochondrial ROS (reactive oxygen species) are highly increased in BRAT1 knockdown HeLa cells. Furthermore, both basal and induced activity of Akt and Erk kinases were suppressed in these cells, implicating abnormality in signaling cascades for cellular growth. Consequently, treatment of BRAT1 knockdown cells with Akt activator can improve their proliferation and reduces mitochondrial ROS concentration.
  
  
  CONCLUSIONS
  These findings suggest novel roles of BRAT1 in cell proliferation and mitochondrial functions.
authors: Eui Young
authors: EY
authors: So
authors: Department of Cancer Genetics, Roswell Park Cancer Institute, Elm and Carlton Streets, 14263 Buffalo, NY, USA. Toru.Ouchi@RoswellPark.org.
authors: Toru
authors: T
authors: Ouchi
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005260:Female; D055785:Gene Knockdown Techniques; D005947:Glucose / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D008928:Mitochondria / Q000378:metabolism*; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction
chemical_list: C573230:BRAT1 protein, human; C000597968:BRAT1 protein, mouse; D009687:Nuclear Proteins; D017382:Reactive Oxygen Species; D000255:Adenosine Triphosphate; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D005947:Glucose