To establish the mechanism by which PDHPS1 controls YAP activity, we analyzed the phosphorylation level of YAP in cells treated by 50 mmol/L PDHPS1 for 48 h. WB results showed that PDHPS1 treatment significantly increased the level of phosphorylated YAP (Fig. 3E). Meanwhile, the mRNA expression levels of CTGF and CYR61, the known YAP-target genes, were significantly down- regulated (Fig. 3F), which further confirmed the inhibitory effect of PDHPS1 on YAP activity. We also analyzed the localization of YAP in the nucleus and cytoplasm, and the results indicated that the nucleus localized YAP was decreased while the cytoplasmic YAP was increased in the PDHPS1 treated ovarian cancer cells (Fig. 3G and H). IHC of subcutaneous tumors in mice also showed that the p-YAP level of PDHPS1-injected group was significantly higher than that of the control group (Fig. 3I and J). In addition, we examined the expression of proteins in Wnt/b-catenin and PI3K/AKT signaling pathways, which are also known regulated by PP2A, and there are no significant differences between control and PDHPS1-treated ovarian cancer cells (Supplementary Fig. S3). Taken together, these results identified PDHPS1 as a regulatory subunit of YAP that regulate ovarian cancer.