Abstract: Objective To study the interaction of PES1 with estrogen recaptor(ER) and its effect on the transactivation activity of ER. Methods GST pull-down was used to verify if PES1 could interact with ERa and ERb in vitro after PES1 was translated and mixed with GST-ERa or GST-ERb purified. The interaction of PES1 with ER in vivo was tested by co-immunoPrecipitation(co-IP) after HA-PES1 was co-transfected with FLAG-ERa? or FLAGC-ERb in 293T cells. The effects of PES1 on ERa and ERb transactivation acitivities were analyzed with estrogen receptor element luciferase. Results PES1 interacted with ERa and ERb in vitro and vivo by GST pull-down and co-IP. PES1 binded ERb strongerly compared to ERa.E2 enhanced the binding of PES1 and ERa but had no effect on that of PES1 and ERb. PES1 raised the transactivation acitivity of ERa and inhibited the transactivation acitivity of ERb in E2-denpent manner. Conclusions PES1 may be a new ER coregulator and can inversely regulate the transactivation acitivities of ERa and ERb. Further researches are needed to elucidate its functions on the ER signaling pathway and on the tumorigenesis and development of E2- induced neoplasms.

Key words: PES1, Estrogen receptor, Ovarian neoplasms, Transactivation