title: The p53-induced Siva-1 plays a significant role in cisplatin-mediated apoptosis.
abstract: BACKGROUND
  The pro-apoptotic protein Siva-1 functions in both extrinsic and intrinsic cell death signaling; however, the exact contribution of the endogenous Siva-1 to DNA damage-induced apoptosis is unclear. Using cisplatin, a chemotherapeutic drug, to induce DNA damage and cell death, we determined the role of Siva-1.
  
  
  METHODS
  Cisplatin treated HCT116 colorectal carcinoma cells (p53+/+ and -/-) were used in the study. With the help of recombinant lentivirus that can express siSiva (siRNA that specifically targets Siva-1), we also generated Siva-1 knockdown HCT116 cells. Apoptosis was determined by tetramethyl rhodamine methyl ester (TMRM) staining and propidium iodide (PI) staining.
  
  
  RESULTS
  Treatment with cisplatin induced Siva-1 expression in a p53 dependent manner. In Siva-1 knockdown p53+/+ HCT116 colorectal carcinoma cells, loss of Siva-1 expression conferred significant resistance to cisplatin-induced apoptosis. Although Siva-1 levels were positively regulated by p53, Siva-1-induced apoptosis did not require p53. Despite the fact that Siva-1 lacks even a minimal BH3 domain, similar to other proapoptotic Bcl2 family members induced by p53, we showed that Siva-1 mediated apoptosis is characterized by Bax oligomerization and cytochrome c leakage from mitochondria. The putative amphipathic helical region in Siva-1 (SAH) appeared to function analogously to a BH3 domain.
  
  
  CONCLUSIONS
  The p53 induced Siva-1 is one of the effector molecules, which plays a significant role in DNA damage-induced cell death.
authors.affiliation: Department of Microbiology and Immunology, University of Illinois at Chicago, 835 S. Wolcott Ave., MC 790, Chicago, IL 60612, USA.
authors.forename: John L
authors.initials: JL
authors.lastname: Barkinge
authors.forename: Radhika
authors.initials: R
authors.lastname: Gudi
authors.forename: Hawkins
authors.initials: H
authors.lastname: Sarah
authors.forename: Fei
authors.initials: F
authors.lastname: Chu
authors.forename: Alip
authors.initials: A
authors.lastname: Borthakur
authors.forename: Bellur S
authors.initials: BS
authors.lastname: Prabhakar
authors.forename: Kanteti V S
authors.initials: KV
authors.lastname: Prasad