Scythe/BAT3 regulates apoptotic cell death induced by papillomavirus binding factor in human osteosarcoma.
Papillomavirus binding factor (PBF) was first identified as a transcription factor regulating the promoter activity of human papillomavirus. We previously demonstrated that PBF is an osteosarcoma-associated antigen and 92% of osteosarcoma tissues express PBF in the nucleus. Moreover, PBF-positive osteosarcoma has a significantly poorer prognosis than that with negative expression of PBF. In the present study, we assessed the biological role of PBF in cell survival. Overexpression of PBF induced cell death-mediated lactate dehydrase (LDH) release from 293EBNA cells. Cleaved poly(ADP-ribose) polymerase and active caspase-3 were also detected. However, PBF-induced apoptosis did not affect caspase-9 activity. Next, to identify the apoptosis regulator of PBF, we screened a cDNA library constructed from mRNA of the osteosarcoma cell line OS2000 using a yeast two-hybrid system and isolated Scythe/BAT3. Scythe/BAT3 mRNA was detected in 56% of osteosarcoma tissues and ubiquitously in various normal tissues. Although Scythe/BAT3 was localized to the cytoplasm in normal tissue, it was localized to the nucleus in osteosarcoma tissue. PBF and Scythe/BAT3 also colocalized to the cytoplasm in 293T cells and the nucleus in OS2000. Furthermore, overexpression of Scythe/BAT3 suppressed cell death events that resulted from overexpression of PBF in OS2000, but not in 293EBNA cells. Thus, our results support the ideas that: (i) PBF could induce apoptotic cell death via a caspase-9-independent pathway; (ii) the apoptosis regulator Scythe/BAT3 is a PBF-associated molecule acting as a nucleus-cytoplasm shuttling protein; and (iii) colocalization of PBF and Scythe/BAT3 in the nucleus might be an important factor for survival of osteosarcoma cells.
Tsukahara
Tomohide
T
Department of Pathology, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-ku, Sapporo 060-8556, Japan. tukahara@sapmed.ac.jp
Kimura
Shigeharu
S
Ichimiya
Shingo
S
Torigoe
Toshihiko
T
Kawaguchi
Satoshi
S
Wada
Takuro
T
Yamashita
Toshihiko
T
Sato
Noriyuki
N
D017209:Apoptosis; D001859:Bone Neoplasms / Q000473:pathology*; D053453:Caspase 9 / Q000502:physiology; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000502:physiology*; D006801:Humans; D018832:Molecular Chaperones; D012516:Osteosarcoma / Q000473:pathology*; D011506:Proteins / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology*
C092009:BAG6 protein, human; D004268:DNA-Binding Proteins; D018832:Molecular Chaperones; D011506:Proteins; D014157:Transcription Factors; C484332:ZNF395 protein, human; D053453:Caspase 9