Our research group had recently found that an endoplasmic reticulum membrane protein, phosphatidylinositol glycan class S (PIGS), interacts with a protein involved in DNA repair, DNA polymerase beta (pol) (using yeast 2 hybrid system), suggesting a role of PIGS in base excision repair pathway. As an essential component of glycosylphosphatidylinositol (GPI) transamidase, PIGS helps many eukaryotic proteins to anchor on the cell surface. In the absence of PIGS, the carbonyl intermediate of GPI is not generated, and GPI biosynthesis remains incomplete. In order to further our understanding of the function of PIGS, we knocked down the gene by using siRNA technology in HeLa cells. The knocked down cell lines were tested for their sensitivity to ultraviolet (UV) radiation and hydrogen peroxide (H2O2) toxicity. The proliferation activity was compared by wound-healing assay. Apoptosis was studied by DNA fragmentation assay, colony forming assay, and caspase assay. Wound healing assay result indicates remarkably higher (1.5-2.7 times) proliferation rate of PIGS knocked down cells. The results from the sensitivity test to UV and H2O2, assessed using DNA fragmentation assay, show that PIGS siRNA cells are more sensitive than the control cells. Apoptosis of these sensitive cells is mediated by the release of cytochrome C in the cytosolic fraction followed by activation of caspase 9, 3 respectively. Therefore, in the future, RNAi technology may be used in the therapy of cervical cancer by depleting PIGS and then treating the patients with UV and H2O2
