PTEN and neoplasm: During tumorigenesis, the reduced nuclear translocation of PTEN impairs its tumor suppressing function, leading to reduced apoptotic cell death, suggesting that PTEN nuclear translocation is causally linked to its apoptotic activity.68 Though PTEN has two important ubiquitination sites K13 and K289 (Figure 2) the C2 domain ubiquitination site PTENK289 neither is involved in nuclear translocation nor in reducing apoptosis.